Search

We present the serendipitous discovery of a galaxy group in the XMM-LSS field with MIGHTEE Early Science observations. 20 galaxies are detected in H i in this z ∼0.044 group, with a 3σ column density sensitivity of NHI = 1.6 × 1020 cm-2. This group has not been previously identified, despite residing in a well-studied extragalactic legacy field. We present spatially resolved H i total intensity and velocity maps for each of the objects which reveal environmental influence through disturbed morphologies. The group has a dynamical mass of log10(Mdyn/M⊙) = 12.32, and is unusually gas-rich, with an H i-to-stellar mass ratio of log10(f∗HI) = -0.2, which is 0.7 dex greater than expected. The group's high H i content, spatial, velocity, and identified galaxy type distributions strongly suggest that it is in the early stages of its assembly. The discovery of this galaxy group is an example of the importance of mapping spatially resolved H i in a wide range of environments, including galaxy groups. This scientific goal has been dramatically enhanced by the high sensitivity, large field-of-view, and wide instantaneous bandwidth of the MeerKAT telescope. © 2021 The Author(s)., The research of SR and RPD is supported by the South African Research Chairs Initiative (grant ID 77948) of the Department of Science and Innovation and National Research Foundation. SR, RPD, and MJJ acknowledge the financial assistance of the South African Radio Astronomy Observatory (SARAO) towards this research (www.ska.ac.za). The HSC instrumentation and software were developed by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IMPU), the University of Tokyo, the High Energy Accelerator Research Organization (KEK), the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA), and Princeton University. Funding was contributed by the FIRST program from Japanese Cabinet Office, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), Japan Science and Technology Agency (JST), the Toray Science Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University. AAP acknowledges the support of the STFC consolidated grant ST/S000488/1. WM is supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation. RB acknowledges support from the Glasstone Foundation and from an STFC Ernest Rutherford Fellowship [grant number ST/T003596/1]. NM acknowledges support from the Bundesministerium für Bildung und Forschung (BMBF) award 05A20WM4. MJJ acknowledges support from the UK Science and Technology Facilities Council [ST/S000488/1 and ST/N000919/1]. MT and MJJ acknowledge support from the Oxford Hintze Centre for Astrophysical Surveys which are funded through generous support from the Hintze Family Charitable Foundation. LVM acknowledges financial support from the grants AYA2015-65973-C3-1-R and RTI2018-096228-B-C31 (MINECO/FEDER, UE), as well as from the State Agency for Research of the Spanish Ministry of Science, Innovation and Universities through the ‘Center of Excellence Severo Ochoa’ award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). This research made use of Astropy,4 a community-developed core PYTHON package for Astronomy. MG and JC acknowledge financial support from the Inter-University Institute for Data Intensive Astronomy (IDIA).

We present the integrated 3-point shear correlation function $i\zeta_{\pm}$ -- a higher-order statistic of the cosmic shear field -- which can be directly estimated in wide-area weak lensing surveys without measuring the full 3-point shear correlation function, making this a practical and complementary tool to 2-point statistics for weak lensing cosmology. We define it as the 1-point aperture mass statistic $M_{\mathrm{ap}}$ measured at different locations on the shear field correlated with the corresponding local 2-point shear correlation function $\xi_{\pm}$. Building upon existing work on the integrated bispectrum of the weak lensing convergence field, we present a theoretical framework for computing the integrated 3-point function in real space for any projected field within the flat-sky approximation and apply it to cosmic shear. Using analytical formulae for the non-linear matter power spectrum and bispectrum, we model $i\zeta_{\pm}$ and validate it on N-body simulations within the uncertainties expected from the sixth year cosmic shear data of the Dark Energy Survey. We also explore the Fisher information content of $i\zeta_{\pm}$ and perform a joint analysis with $\xi_{\pm}$ for two tomographic source redshift bins with realistic shape-noise to analyse its power in constraining cosmological parameters. We find that the joint analysis of $\xi_{\pm}$ and $i\zeta_{\pm}$ has the potential to considerably improve parameter constraints from $\xi_{\pm}$ alone, and can be particularly useful in improving the figure of merit of the dynamical dark energy equation of state parameters from cosmic shear data.

We report on the stellar content, half-light radii and star formation rates of a sample of 10 known high-redshift ($z\gtrsim 2$) galaxies selected on strong neutral hydrogen (HI) absorption (log(N(HI)/cm$^{-2})>19$) toward background quasars. We use observations from the {\it Hubble Space Telescope} (HST) Wide Field Camera 3 in three broad-band filters to study the spectral energy distribution(SED) of the galaxies. Using careful quasar point spread function subtraction, we study their galactic environments, and perform the first systematic morphological characterisation of such absorption-selected galaxies at high redshifts. Our analysis reveals complex, irregular hosts with multiple star-forming clumps. At a spatial sampling of 0.067 arcsec per pixel (corresponding to 0.55 kpc at the median redshift of our sample), 40% of our sample requires multiple S��rsic components for an accurate modelling of the observed light distributions. Placed on the mass-size relation and the `main sequence' of star-forming galaxies, we find that absorption-selected galaxies at high redshift extend known relations determined from deep luminosity-selected surveys to an order of magnitude lower stellar mass, with objects primarily composed of star-forming, late-type galaxies. We measure half-light radii in the range $r_{1/2} \sim$ 0.4 to 2.6 kpc based on the reddest band (F160W) to trace the oldest stellar populations, and stellar masses in the range $\log (\mathrm{M}_{\star}/\mathrm{M}_{\odot}) \sim$ 8 to 10 derived from fits to the broad-band SED. Spectroscopic and SED-based star formation rates are broadly consistent, and lie in the range log(SFR/M$_{\odot} $yr$^{-1}$) $\sim$0.0 to 1.7., 17 pages, Accepted for publication in MNRAS. This revision has minor text changes

We characterize the conditional distributions of the HI gas-to-stellar mass ratio, $R_{HI}\equiv M_{HI}/M_{\ast}$, given the stellar mass, $M_{\ast}$, of local galaxies from $M_{\ast}\sim 10^7$ to $10^{12}$ $M_{\odot}$ separated into centrals and satellites as well as into late- and early-type galaxies (LTGs and ETGs, respectively). To do so, we use (1) the homogeneous "eXtended GALEX Arecibo SDSS Survey", xGASS (Catinella et al. 2018), by re-estimating their upper limits and taking into account them in our statistical analysis; and (2) the results from a large compilation of HI data reported in Calette et al. (2018). We use the $R_{HI}$ conditional distributions combined with the Galaxy Stellar Mass Function to infer the bivariate $M_{HI}$ and $M_{\ast}$ distribution of all galaxies as well of the late/early-type and central/satellite subsamples and their combinations. Satellites are on average less HI gas-rich than centrals at low and intermediate masses, with differences being larger for ETGs than LTGs; at $M_{\ast}>3-5\times 10^{10}$ $M_{\odot}$ the differences are negligible. The differences in the HI gas content are much larger between LTGs and ETGs than between centrals and satellites. Our empirical HI Mass Function is strongly dominated by central galaxies at all masses. The empirically constrained bivariate $M_{HI}$ and $M_{\ast}$ distributions presented here can be used to compare and constrain theoretical predictions as well as to generate galaxy mock catalogues., In press, 21 pages, 15 figures. Minor corrections in text, results unchanged. Supplementary material available at ancillary files

We explore the potential of the kinetic Sunyaev-Zel'dovich (kSZ) effect as the cornerstone of a future observational probe for halo spin bias, the secondary dependence of halo clustering on halo spin at fixed halo mass. Using the IllustrisTNG magneto-hydrodynamical cosmological simulation, we measure both the kSZ and the thermal SZ (tSZ) effects produced by the baryonic content of more than 50,000 haloes within the halo mass range $11 < \log_{10} ({\rm M_{vir}}/ h^{-1} {\rm M_{\odot}}) \lesssim 14.5$. First, we confirm that the magnitude of both effects depends strongly on the total gas and virial mass of the haloes, and that the integrated kSZ signal displays a significant correlation with the angular momentum of the intra-halo gas, particularly for massive haloes. Second, we show that both the integrated kSZ signal and the ratio of the integrated kSZ and tSZ signals trace total halo spin, even though significant scatter exists. Finally, we demonstrate that, in the absence of observational and instrumental uncertainties, these SZ-related statistics can be used to recover most of the underlying IllustrisTNG halo spin bias signal. Our analysis represents the first attempt to develop a future observational probe for halo spin bias, bringing forward alternative routes for measuring the secondary bias effects., 17 pages, 10 figures, submitted to MNRAS

The inflow of cosmological gas onto haloes, while challenging to directly observe and quantify, plays a fundamental role in the baryon cycle of galaxies. Using the EAGLE suite of hydrodynamical simulations, we present a thorough exploration of the physical properties of gas accreting onto haloes -- namely, its spatial characteristics, density, temperature, and metallicity. Classifying accretion as ``hot'' or `` cold'' based on a temperature cut of $10^{5.5}{\rm K}$, we find that the covering fraction ($f_{\rm cov}$) of cold-mode accreting gas is significantly lower than the hot-mode, with $z=0$ $f_{\rm cov}$ values of $\approx 50\%$ and $\approx 80\%$ respectively. Active Galactic Nuclei (AGN) feedback in EAGLE reduces inflow $f_{\rm cov}$ values by $\approx 10\%$, with outflows decreasing the solid angle available for accretion flows. Classifying inflow by particle history, we find that gas on first-infall onto a halo is metal-depleted by $\approx 2$~dex compared to pre-processed gas, which we find to mimic the circum-galactic medium (CGM) in terms of metal content. We also show that high (low) halo-scale gas accretion rates are associated with metal-poor (rich) CGM in haloes below $10^{12}M_{\odot}$, and that variation in halo-scale gas accretion rates may offer a physical explanation for the enhanced scatter in the star-forming main sequence at low ($\lesssim10^{9}M_{\odot}$) and high ($\gtrsim10^{10}M_{\odot}$) stellar masses. Our results highlight how gas inflow influences several halo- and galaxy-scale properties, and the need to combine kinematic and chemical data in order to confidently break the degeneracy between accreting and outgoing gas in CGM observations., 24 pages, 13 figures. Final version accepted for publication in MNRAS

We constrain the mass distribution in nearby, star-forming galaxies with the Star Formation Reference Survey (SFRS), a galaxy sample constructed to be representative of all known combinations of star formation rate (SFR), dust temperature, and specific star formation rate (sSFR) that exist in the Local Universe. An innovative two-dimensional bulge/disk decomposition of the 2MASS/$K_{s}$-band images of the SFRS galaxies yields global luminosity and stellar mass functions, along with separate mass functions for their bulges and disks. These accurate mass functions cover the full range from dwarf galaxies to large spirals, and are representative of star-forming galaxies selected based on their infra-red luminosity, unbiased by AGN content and environment. We measure an integrated luminosity density $j$ = 1.72 $\pm$ 0.93 $\times$ 10$^{9}$ L$_{\odot}$ $h^{-1}$ Mpc$^{-3}$ and a total stellar mass density $\rho_{M}$ = 4.61 $\pm$ 2.40 $\times$ 10$^{8}$ M$_{\odot}$ $h^{-1}$ Mpc$^{-3}$. While the stellar mass of the \emph{average} star-forming galaxy is equally distributed between its sub-components, disks globally dominate the mass density budget by a ratio 4:1 with respect to bulges. In particular, our functions suggest that recent star formation happened primarily in massive systems, where they have yielded a disk stellar mass density larger than that of bulges by more than 1 dex. Our results constitute a reference benchmark for models addressing the assembly of stellar mass on the bulges and disks of local ($z = 0$) star-forming galaxies., Comment: 33 pages, 21 figures, published in MNRAS, 504, 3831-3861 (2021)

We present a panchromatic study of 11 (sub-)millimetre selected DSFGs with spectroscopically confirmed redshift ($1.5< z_{\rm spec}, Comment: 23 pages, 6 figures, 13 tables. Accepted for publication in MNRAS

We examine how the post-processed content of molecular hydrogen (H$_2$) in galaxies from the TNG100 cosmological, hydrodynamic simulation changes with environment at $z\!=\!0$, assessing central/satellite status and host halo mass. We make close comparisons with the carbon monoxide (CO) emission survey xCOLD GASS where possible, having mock-observed TNG100 galaxies to match the survey's specifications. For a representative sample of host haloes across $10^{11}\!\lesssim\!M_{\rm 200c}/{\rm M}_{\odot}\!, Comment: Accepted in MNRAS. Minor proofing and reference edits from v1. Main body: 19 pages, 11 figures

Accurate stellar parameters of stars in open clusters can help constrain models of stellar structure and evolution. Here we wish to determine the age and metallicity content of the open cluster NGC 2506. To this end we investigated three detached eclipsing binaries (DEBs; V2032, V4, and V5) for which we determined their masses and radii, as well as four red giant branch stars for which we determined their effective temperatures, surface gravities, and metallicities. Three of the stars in the DEBs have masses close to the cluster turn-off mass, allowing for extremely precise age determination. Comparing the values for the masses and radii of the binaries to BaSTI isochrones we estimated a cluster age of $2.01 \pm 0.10$ Gyr. This does depend on the models used in the comparison, where we have found that the inclusion of convective core-overshooting is necessary to properly model the cluster. From red giant branch stars we determined values for the effective temperatures, the surface gravities, and the metallicities. From these we find a cluster metallicity of $-0.36 \pm 0.10$ dex. Using this value and the values for the effective temperatures we determine the reddening to be E$(b - y) = 0.057 \pm 0.004$ mag. Furthermore, we derived the distance to the cluster from Gaia parallaxes and found $3.101 \pm 0.017$ kpc, and we have performed a radial velocity membership determination for stars in the field of the cluster. Finally, we report on the detection of oscillation signals in $\gamma$ Dor and $\delta$ Scuti members in data from the TESS mission, including the possible detection of solar-like oscillations in two of the red giants., Comment: 30 pages, 16 figures, accepted for publication in MNRAS

We introduce a new methodology for efficiently tuning sub-grid models of star formation and supernovae feedback in cosmological simulations and at the same time understanding their physical implications. Based on a set of 71 zoom simulations of a Milky Way (MW)-sized halo, we explore the feasibility of calibrating a widely used star formation and feedback model in the enzo simulation code. We propose a novel way to match observations, using functional fits to the observed baryon makeup over a wide range of halo masses. The model MW galaxy is calibrated using three parameters: the star formation efficiency (f*), the efficiency of thermal energy from stellar feedback (ϵ), and the region into which feedback is injected (r and s). We find that changing the amount of feedback energy affects the baryon content most significantly. We then identify two sets of feedback parameter values that are both able to reproduce the baryonic properties for haloes between $10^{10}\, \mathrm{M_\odot }$ and $10^{12}\, \mathrm{M_\odot }$. We can potentially improve the agreement by incorporating more parameters or physics. If we choose to focus on one property at a time, we can obtain a more realistic halo baryon makeup. Contrasting both star formation criteria and the corresponding combination of optimal feedback parameters, we also highlight that feedback effects can be complementary: to match the same baryonic properties, with a relatively higher gas-to-stars conversion efficiency, the feedback strength required is lower, and vice versa. Lastly, we demonstrate that chaotic variance in the code can cause deviations of approximately 10 per cent and 25 per cent in the stellar and baryon mass in simulations evolved from identical initial conditions.

We use the EAGLE suite of hydrodynamical simulations to analyse accretion rates (and the breakdown of their constituent channels) onto haloes over cosmic time, comparing the behaviour of baryons and dark matter (DM). We also investigate the influence of sub-grid baryon physics on halo-scale inflow, specifically the consequences of modelling radiative cooling, as well as feedback from stars and active galactic nuclei (AGN). We find that variations in halo baryon fractions at fixed mass (particularly their circum-galactic medium gas content) are very well correlated with variations in the baryon fraction of accreting matter, which we show to be heavily suppressed by stellar feedback in low-mass haloes, $M_{\rm halo}\lesssim10^{11.5}M_{\odot}$. Breaking down accretion rates into first infall, recycled, transfer and merger components, we show that baryons are much more likely to be smoothly accreted than to have originated from mergers when compared to DM, finding (averaged across halo mass) a merger contribution of $\approx6\%$ for baryons, and $\approx15\%$ for DM at $z\approx0$. We also show that the breakdown of inflow into different channels is strongly dependent on sub-grid physics, particularly the contribution of recycled accretion (accreting matter that has been previously ejected from progenitor haloes). Our findings highlight the dual role that baryonic feedback plays in regulating the evolution of galaxies and haloes: by (i) directly removing gas from haloes, and (ii) suppressing gas inflow to haloes., Final version accepted for publication by MNRAS. 24 pages, 10 figures

We use dust masses ($M_{dust}$) derived from far-infrared data and molecular gas masses ($M_{mol}$) based on CO luminosity, to calibrate proxies based on a combination of the galaxy Balmer decrement, disk inclination and gas metallicity. We use such proxies to estimate $M_{dust}$ and $M_{mol}$ in the local SDSS sample of star-forming galaxies (SFGs). We study the distribution of $M_{dust}$ and $M_{mol}$ along and across the Main Sequence (MS) of SFGs. We find that $M_{dust}$ and $M_{mol}$ increase rapidly along the MS with increasing stellar mass ($M_*$), and more marginally across the MS with increasing SFR (or distance from the relation). The dependence on $M_*$ is sub-linear for both $M_{dust}$ and $M_{mol}$. Thus, the fraction of dust ($f_{dust}$) and molecular gas mass ($f_{mol}$) decreases monotonically towards large $M_*$. The star formation efficiency (SFE, the inverse of the molecular gas depletion time) depends strongly on the distance from the MS and it is constant along the MS. As nearly all galaxies in the sample are central galaxies, we estimate the dependence of $f_{dust}$ and $f_{gas}$ on the host halo mass and find a tight anti-correlation. As the region where the MS is bending is numerically dominated by massive halos, we conclude that the bending of the MS is due to lower availability of molecular gas mass in massive halos rather than a lower efficiency in forming stars., Accepted for publication in MNRAS, 12 pages, 9 figures

Using deep images from the Hyper Suprime-Cam (HSC) survey and taking advantage of its unprecedented weak lensing capabilities, we reveal a remarkably tight connection between the stellar mass distribution of massive central galaxies and their host dark matter halo mass. Massive galaxies with more extended stellar mass distributions tend to live in more massive dark matter haloes. We explain this connection with a phenomenological model that assumes, (1) a tight relation between the halo mass and the total stellar content in the halo, (2) that the fraction of in-situ and ex-situ mass at $r, 22 Pages, 12 Figures, 1 Table; Submitted to MNRAS. The model and Jupyter notebooks to reproduce the figures are available here: https://github.com/dr-guangtou/asap

Growing observational evidence confirms the existence of massive black holes ($M_{BH} \sim 10^9 M_{\odot}$), accreting at rates close to the Eddington limit, at very high redshifts ($z \gtrsim 6-7$) in the early Universe. Recent observations indicate that the host galaxies of the first quasars are chemically evolved systems, containing unexpectedly large amounts of dust. Such a combination of high luminosities and large dust content should form favourable physical conditions for radiative dusty feedback. We explore the impact of the active galactic nucleus (AGN) feedback, driven by radiation pressure on dust, on the early growth of massive black holes. Assuming Eddington-limited exponential black hole growth, we find that the dynamics and energetics of the radiation pressure-driven outflows also follow exponential trends at late times. We obtain modest outflow energetics (with momentum flux $\dot{p} \lesssim L/c$ and kinetic power $\dot{E}_{k} \lesssim 10^{-3} L$), comparable with available observations of quasar-driven outflows at very high redshifts, but significantly lower than typically observed in local quasars and predicted by wind energy-driven models. AGN radiative dusty feedback may thus play an important role in powering galactic outflows in the first quasars in the early Universe., Comment: MNRAS, in press

The origin of dust in galaxy halos or in the circum-galactic medium (CGM) is still a mystery. We investigate if the radiation pressure in high-redshift ($z\sim 10$) galaxies can efficiently transport dust to halos. To clarify the first dust enrichment of galaxy halos in the early Universe, we solve the motion of a dust grain considering radiation pressure, gas drag, and gravity in the vertical direction of the galactic disc. Radiation pressure is estimated in a consistent manner with the stellar spectra and dust extinction. As a consequence, we find that dust grains with radii $a\sim 0.1~\mu$m successfully escape from the galactic disc if the ongoing star formation episode converts more than 15 per cent of the baryon content into stars and lasts $\gtrsim 30$ Myr, while larger and smaller grains are trapped in the disc because of gravity and gas drag, respectively. We also show that grain charge significantly enhances gas drag at a few--10 scale heights of the galactic disc, where the grain velocities are suppressed to $\sim 1$ km s$^{-1}$. There is an optimum dust-to-gas ratio ($\sim 10^{-3}$) in the galactic disc and an optimum virial mass $\sim 10^{10}$--$10^{11}$ M$_{\odot}$ for the transport of $a\sim 0.1~\mu$m grains to the halo. We conclude that early dust enrichment of galaxy halos at $z\gtrsim 10$ is important for the origin of dust in the CGM., Comment: 14 pages, 8 figures, accepted for publication in MNRAS

The study of the "chromosome maps" of Galactic Globular Clusters has shown that the stars identified as `first generation' often define an extended sequence in the $m_{F275W}-m_{F814W}$ colour, whose straightforward interpretation, by comparison with synthetic spectra, is that they are inhomogeneous in helium content. The cluster M 3 (NGC 5272) is one of the most prominent example of this phenomenon, since its first generation is distributed on an extended colour range, formally corresponding to a large helium enhancement ($ \sim 0.1$). It is necessary to ask whether the bulk of photometric observations available for this cluster supports or falsifies this interpretation. For this purpose, we examine the horizontal branch morphology, the period and magnitude distributions of the RR Lyrae variables, and the main sequence colour distribution. Simulating the first generation stars with such internal variation of helium content we can not meet all the observational constraints at the same time, concluding that the origin of the first generation colour spread is still without a straightforward explanation., Comment: 13 pages, 9 figures, 2 tables. Accepted for publication in MNRAS

We investigate the connection between the HI~content, SFR and environment of galaxies using a hydrodynamic simulation that incorporates scaling relations for galactic wind and a heuristic halo mass-based quenching prescription. We run two zoom-in simulations of galaxy groups with $M_{halo}>10^{13}M_\odot$ at z=0, selected to have quiet merger histories. We track galaxies as they become satellites, and compute the delay time $\tau_{d}$ during which the satellites are similar to central galaxies at a given stellar mass, and a fading time $\tau_{f}$ during which satellites go from gas-rich and star-forming to gas-poor and quiescent. We find $0.7< \tau_{d}< 3$ Gyr at $z=0$, and depends inversely on the satellite halo mass at infall. At z ~ 1 we find ~$0.3< \tau_{d} < 2$ Gyr, broadly consistent with a positive correlation with the Hubble time. For a given halo mass, lower stellar mass galaxies at infall time have higher $\tau_{d}$. We generally find $\tau_{f}\ll \tau_{d}$, ranging between ~ 150 Myr at z~0 and ~ 80 Myr at z ~ 1 based on linear interpolation, with some uncertainty because they are smaller than our simulation output frequency ($200-300$ Myr). $\tau_{f}$ has no obvious dependency on infall halo mass. Both timescales show little difference between HI depletion and SF quenching, indicating that using up the gas reservoir by star formation without refilling is the main mechanism to transform satellite galaxies at these halo masses. At a given physical distance from the center of the main halo of interest, higher redshift galaxies have on average higher cold gas content, but the ratio of gas (HI or H$_2$) to star formation rate is similar, indicating that star formation is consistently fed through reservoirs of HI then H$_2$. For a given amount of HI, galaxies have shorter consumption times in more massive halo structures.

We have used the NIHAO simulations to explore how supernovae (SNe) affect star formation in galaxies. We find that SN feedback operates on all scales from the interstellar medium (ISM) to several virial radii. SNe regulate star formation by preventing condensation of HI into H$_2$ and by moving cold neutral gas to the hot HII phase. The first effect explains why the cold neutral gas in dwarf galaxies forms stars inefficiently. The second maintains the hot ISM of massive galaxies (HII vents out at lower masses). At $v_{\rm vir}\simeq 67{\rm\,km\,s}^{-1}$, the outflow rate follows the relation: $\dot{M}_{\rm out}=23\,(v_{\rm vir}/67{\rm\,km\,s}^{-1})^{-4.6}\,{\rm SFR}$. $20\%$ to $70\%$ of the gas expelled from galaxies escapes from the halo (ejective feedback) but outflows are dominated by cold swept-up gas, most of which falls back onto the galaxy on a $\sim 1\,$Gyr timescale. This `fountain feedback' reduces the masses of galaxies by a factor of two to four, since gas spends half to three quarter of its time in the fountain. Less than $10\%$ of the ejected gas mixes with the hot circumgalactic medium and this gas is usually not reaccreted. On scales as large as $6r_{\rm vir}$, galactic winds divert the incoming gas from cosmic filaments and prevent if from accreting onto galaxies (pre-emptive feedback). This process is the main reason for the low baryon content of ultradwarves., Comment: Submitted for publication in MNRAS

We present new cosmological hydrodynamic simulations that incorporate Dark Matter Annihilation Feedback (DMAF), whereby energy released from the annihilation of dark matter particles through decay channels such as photon or positron-electron pairs provide additional heating sources for local baryonic material. For annihilation rates comparable to WIMP-like particles, we find that the key influence of DMAF is to inhibit gas accretion onto halos. Such diminished gas accretion early in the lifetimes of halos results in reduced gas fractions in smaller halos, and the delayed halo formation times of larger structures, suggesting that DMAF could impact the stellar age distribution in galaxies, and morphology of dwarfs. For a dark matter particle mass of $m_\chi\sim10$~MeV, there is a `critical halo mass' of $\sim10^{13}$ M$_{\odot}$ at $z=0$, below which there are large differences when compared to $\Lambda$CDM, such as a reduction in the abundance of halo structures as large as 25 percent, reduced gas content by 50 percent and central gas densities reduced down to 10 percent within halos of mass $\sim10^{12}$ M$_{\odot}$ but with increasing effects in smaller halos. Higher dark matter particle mass models have a smaller `critical halo mass'. For a $m_\chi\sim100$~MeV model, we find differences start appearing below halo masses of $\sim10^{12}$ M$_\odot$ and a $m_\chi\gtrsim 1$~GeV model, this mass scale lies below the resolution of our simulations, though we still observe changes in the morphology of dwarf galaxies., Comment: 16 pages, 12 figures

We study the environmental properties of z10^{23.5} W Hz^{-1} sr^{-1}$ are twice more likely to be found in clusters with respect to fainter sources (~38% vs ~15%), just as radio-selected AGN with stellar masses $M*>10^{11} M_\odot$ are twice more likely to be found in overdense environments with respect to objects of lower mass (~24% vs ~11%). Comparisons with galaxy samples further suggest that radio-selected AGN of large stellar mass tend to avoid underdense environments more than normal galaxies with the same stellar content. Stellar masses also seem to determine the location of radio-active AGN within clusters: ~100% of the sources found as satellite galaxies have $M*10^{11} M_\odot$. No different location within the cluster is instead observed for AGN of various radio luminosities. Radio AGN which also emit in the MIR show a marked preference to be found as isolated galaxies (~70%) at variance with those also active in the X-ray which all seem to reside within overdensities. What emerges from our work is a scenario whereby physical processes on sub-pc and kpc scales (e.g. emission respectively related to the AGN and to star formation) are strongly interconnected with the large-scale environment of the AGN itself., 8 pages, 6 figures, to appear on MNRAS

We present the cold neutral content (H I and C I gas) of 13 quasar 2175 \AA$ $ dust absorbers (2DAs) at $z$ = 1.6 - 2.5 to investigate the correlation between the presence of the UV extinction bump with other physical characteristics. These 2DAs were initially selected from the Sloan Digital Sky Surveys I - III and followed up with the Keck-II telescope and the Multiple Mirror Telescope as detailed in our Paper I. We perform a correlation analysis between metallicity, redshift, depletion level, velocity width, and explore relationships between 2DAs and other absorption line systems. The 2DAs on average have higher metallicity, higher depletion levels, and larger velocity widths than Damped Lyman-$\alpha$ absorbers (DLAs) or subDLAs. The correlation between [Zn/H] and [Fe/Zn] or [Zn/H] and log$\Delta$V$_{90}$ can be used as alternative stellar mass estimators based on the well-established mass-metallicity relation. The estimated stellar masses of the 2DAs in this sample are in the range of $\sim$ 10$^9$ to $\sim$2 $\times$ 10$^{11}$ $M_{\odot}$ with a median value of $\sim$2 $\times$ 10$^{10}$ $M_{\odot}$. The relationship with other quasar absorption line systems can be described as (1) 2DAs are a subset of Mg II and Fe II absorbers, (2) 2DAs are preferentially metal-strong DLAs/subDLAs, (3) More importantly, all of the 2DAs show C I detections with logN(C I) $>$ 14.0 cm$^{-2}$, (4) 2DAs can be used as molecular gas tracers. Their host galaxies are likely to be chemically enriched, evolved, massive (more massive than typical DLA/subDLA galaxies), and presumably star-forming galaxies., Comment: 12 pages, 11 figures; accepted for publication in MNRAS

In this paper, we stack neutral atomic hydrogen (HI) spectra for 9,720 star forming galaxies along the mass-metallicity relation. The sample is selected according to stellar mass (10$^9 \leq$ M$_{\star}$/M$_{\odot}\leq$10$^{11}$) and redshift ($0.02 \leq z \leq 0.05$) from the overlap of the Sloan Digital Sky Survey and Arecibo Legacy Fast ALFA survey. We confirm and quantify the strong anti-correlation between HI mass and gas-phase metallicity at fixed stellar mass. Furthermore, we show for the first time that the relationship between gas content and metallicity is consistent between different metallicity estimators, contrary to the weaker trends found with star formation which are known to depend on the observational techniques used to derive oxygen abundances and star formation rates. When interpreted in the context of theoretical work, this result supports a scenario where galaxies exist in an evolving equilibrium between gas, metallicity and star formation. The fact that deviations from this equilibrium are most strongly correlated with gas mass suggests that the scatter in the mass-metallicity relation is primarily driven by fluctuations in gas accretion., Accepted to MNRAS, 12 pages, 5 figures

We study the gas and stellar mass content of galaxy groups and clusters in the FABLE suite of cosmological hydrodynamical simulations, including the evolution of their central brightest cluster galaxies (BCGs), satellite galaxies and intracluster light (ICL). The total gas and stellar mass of FABLE clusters are in very good agreement with observations and show negligible redshift evolution at fixed halo mass for $M_{500} \gtrsim 3 \times 10^{14} M_{\odot}$ at $z \lesssim 1$, in line with recent findings from Sunyaev-Zel'dovich (SZ)-selected cluster samples. Importantly, the simulations predict significant redshift evolution in these quantities in the low mass ($M_{500} \sim 10^{14} M_{\odot}$) regime, which will be testable with upcoming SZ surveys such as SPT-3G. While the stellar masses of FABLE BCGs are in reasonable agreement with observations, the total stellar mass in satellite galaxies is lower than observed and the total mass in ICL is somewhat higher. This may be caused by enhanced tidal stripping of satellite galaxies due to their large sizes. BCGs are characterised by moderate stellar mass growth at $z < 1$ coincident with a late-time development of the ICL. The level of BCG mass growth is in good agreement with recent observations, however, we caution that the inferred growth depends sensitively on the mass definition. We further show that in-situ star formation contributes more than half the mass of a BCG over its lifetime, the bulk of which is gained at $z > 1$ where star formation rates are highest. The stellar mass profiles of the BCG+ICL component are similar to observed profiles out to $\sim 100$ kpc at $z \approx 0$ and follow a close to power law shape out to several hundred kpc. We further demonstrate that the inferred size growth of BCGs can be severely biased by the choice of parametric model and the outer radius of the fit., 27 pages, 13 figures, 1 appendix; MNRAS accepted

We report the detection of thermal Sunyaev-Zeldovich effect (SZ) fluctuations in the intracluster medium (ICM) of Coma cluster observed with ${\it Planck}$. The SZ data links the maximum observable X-ray scale to the large Mpc scale, extending our knowledge of the power spectrum of ICM fluctuations. Deprojecting the 2-d SZ perturbations into 3-d pressure fluctuations, we find an amplitude spectrum which peaks at $\delta P/P = 33\pm 12\%$ and $74\pm19\%$ in the $15'$ and $40'$ radius region, respectively. We perform tests to ensure fluctuations are intrinsic to the cluster and not due to noise contamination. By using high-resolution hydrodynamical models, we improve the ICM turbulence constraints in Coma, finding 3-d Mach number ${\rm Ma_{3d}}= 0.8\pm0.3$ (15' region), increasing to supersonic values at larger radii (40'), and an injection scale $L_{\rm inj}\approx 500$ kpc. Such properties are consistent with driving due to mergers, in particular tied to internal galaxy groups. The large pressure fluctuations show that Coma is in adiabatic mode (mediated by sound waves), rather than isobaric mode (mediated by buoyancy waves). As predicted by turbulence models, the distribution of SZ fluctuations is log-normal with mild non-Gaussianities (heavy tails). The substantial non-thermal pressure support implies hydrostatic mass bias $b_M=-15\%$ to $-45\%$ from the core to the outskirt region, respectively. While total SZ power probes the thermal energy content, the SZ fluctuations constrain the non-thermal deviations important for precision cosmology. The proposed, novel approach can be exploited by multifrequency observations using ground based interferometers and future space CMB missions., Comment: Accepted version

We present our multiwavelength analysis of a prototype \HI-excess galaxy, GASS 3505, selected based on having a large gas content ($M_{\rm HI} = 10^{9.9}$ \msun) compared to its little associated star formation activity ($\sim$0.1 \msun\ yr$^{-1}$) in the GALEX Arecibo SDSS Survey (GASS). Very Large Array (VLA) observations show that the \HI\ in GASS 3505 is distributed in a regularly rotating, extended ($\sim$50 kpc radius) gas ring. In the SDSS optical image GASS 3505 appears as a bulge-dominated galaxy, however deep optical imaging reveals low surface brightness ($\gtrsim25$ mag arcsec$^{-2}$) stellar emission around the central bulge. Direct evidence for accretion is detected in form of an extended ($\sim$60 kpc) stellar stream, showing that GASS 3505 has experienced a minor merger in the recent past. We investigate the possibility that the \HI\ ring in GASS 3505 was accreted in such a merger event using N-body and smoothed particle hydrodynamic (SPH) simulations. The best model that reproduces the general properties (i.e., gas distribution and kinematics, stellar morphology) of the galaxy involves a merger between the central bulge and a gas-rich ($M_{\star}$ = 10$^9$ \msun\ and $M_{\rm HI}$/$M_{\star}$ = 10) disk galaxy. However, small discrepancies in the observed and modeled properties could suggest that other sources of gas have to be involved in the build-up of the gas reservoir. This work is the first step toward a larger program to investigate the physical mechanisms that drive the large scatter in the gas scaling relations of nearby galaxies., Comment: Accepted for publication in MNRAS

Despite being $>10$Myr, there are $\sim$10 debris discs with as much CO gas as in protoplanetary discs. Such discs have been assumed to be "hybrid", i.e., with secondary dust but primordial gas. Here we show that both the dust and gas in such systems could instead be secondary, with the high CO content caused by accumulation of neutral carbon (C$^0$) that shields CO from photodissociating; i.e., these could be "shielded secondary discs". New ALMA observations are presented of HD131835 that detect $\sim 3 \times 10^{-3}$ M$_\oplus$ of C$^0$, the majority 40-200au from the star, in sufficient quantity to shield the previously detected CO. A simple semi-analytic model for the evolution of CO, C and O originating in a volatile-rich planetesimal belt shows how CO shielding becomes important when the viscous evolution is slow (low $\alpha$ parameter) and/or the CO production rate is high. Shielding by C$^0$ may also cause the CO content to reach levels at which CO self-shields, and the gas disc may become massive enough to affect the dust evolution. Application to the HD 131835 observations shows these can be explained if $\alpha \sim 10^{-3}$; an inner cavity in C$^0$ and CO may also mean the system has yet to reach steady state. Application to other debris discs with high CO content finds general agreement for $\alpha=10^{-3}$ to $0.1$. The shielded secondary nature of these gas discs can be tested by searching for C$^0$, as well as CN, N$_2$ and CH$^{+}$, which are also expected to be shielded by C$^0$., Comment: accepted to MNRAS

Globular clusters (GCs) are the ideal environment for the formation of neutron stars (NSs) and millisecond pulsars (MSPs). NSs origin and evolution provide a useful information on stellar dynamics and evolution in star clusters, and are among the most interesting astrophysical objects, being precursors of several high-energy phenomena such as gravitational waves and gamma-ray bursts. Due to a large velocity kick that they receive at birth, most of the NSs escape the local field, affecting the evolution and dynamics of their parent cluster. In this paper, we study the origin and dynamical evolution of NSs within GCs with different initial masses, metallicities and primordial binary fractions. We find that the radial profile of NSs is shaped by the BH content of the cluster, which partially quenches the NS segregation until most of the BHs are ejected from the system. Independently on the cluster mass and initial configuration, the NSs map the average stellar population, as their average radial distance is $\approx 60-80\%$ of the cluster half-mass radius. Finally, by assuming a recycling fraction of $f_\mathrm{rec}=0.1$ and an average MSP gamma-ray emission of $L_\gamma=2\times 10^{33}$ erg s$^{-1}$, we show that the typical gamma-ray emission from our GCs agrees with observations and supports the MSP origin of the gamma-ray excess signal observed by the Fermi-LAT telescope in the Galactic Centre., Comment: 9 pages, 4 figures, 2 Tables, accepted by MNRAS

We provide a new view on the Cygnus-X north complex by accessing for the first time the low mass content of young stellar populations in the region. CFHT/WIRCam camera was used to perform a deep near-IR survey of this complex, sampling stellar masses down to ~0.1 M$_\odot$. Several analysis tools, including a extinction treatment developed in this work, were employed to identify and uniformly characterise a dozen unstudied young star clusters in the area. Investigation of their mass distributions in low-mass domain revealed a relatively uniform log-normal IMF with a characteristic mass of 0.32$\pm$0.08 M$_\odot$ and mass dispersion of 0.40$\pm$0.06. In the high mass regime, their derived slopes showed that while the youngest clusters (age < 4 Myr) presented slightly shallower values with respect to the Salpeter's, our older clusters (4 Myr < age < 18 Myr) showed IMF compliant values and a slightly denser stellar population. Although possibly evidencing a deviation from an 'universal' IMF, these results also supports a scenario where these gas dominated young clusters gradually 'build up' their IMF by accreting low-mass stars formed in their vicinity during their first ~3 Myr, before the gas expulsion phase, emerging at the age of ~4 Myr with a fully fledged IMF. Finally, the derived distances to these clusters confirmed the existence of at least 3 different star forming regions throughout Cygnus-X north complex, at distances of 500-900 pc, 1.4-1.7 kpc and 3.0 kpc, and revealed evidence of a possible interaction between some of these stellar populations and the Cygnus-OB2 association.

We have probed the pulsating variable star content of the isolated Local Group dwarf galaxy, DDO210 (Aquarius), using archival Advanced Camera for Surveys/$Hubble$ $Space$ $Telescope$ imaging in the F475W and F814W passbands. We find a total of 32 RR Lyrae stars (24 ab-type, 8 c-type) and 75 Cepheid variables. The mean periods of the ab-type and c-type RR Lyrae stars are calculated to be $\langle$P$_{\mathrm{ab}}\rangle = 0.609\pm0.011$ and $\langle$P$_{\mathrm{c}}\rangle = 0.359\pm0.025$ days, respectively. The light curve properties of the fundamental mode RR Lyrae stars yield a mean metallicity of $\langle$[Fe/H]$\rangle$ = -1.63$\pm$0.11 dex for this ancient population, consistent with a recent synthetic colour-magnitude diagram analysis. We find this galaxy to be Oosterhoff-intermediate and lacking in high-amplitude, short-period ab-type RR Lyrae, consistent with behavior recently observed for many dwarf spheroidals and ultra-faint dwarfs in the Local Group. We find a distance modulus of $\mu = 25.07\pm 0.12$ as determined by the RR Lyrae stars, slightly larger but agreeing with recent distance estimates from the red giant branch tip. We also find a sizable population of Cepheid variables in this galaxy. We provide evidence in favor of most if not all of these stars being short-period classical Cepheids. Assuming all of these stars to be classical Cepheids, we find that most of these Cepheids are $\sim$300 Myr old, with the youngest Cepheids being offset from the older Cepheids and the centre of the galaxy. We conclude that this may have resulted from a migration of star formation in DDO210., Comment: Accepted for publication into MNRAS, 17 pages, 13 figures, 4 tables

The thermal Sunyaev-Zel'dovich (tSZ) effect offers a means of probing the hot gas in and around massive galaxies and galaxy groups and clusters, which is thought to constitute a large fraction of the baryon content of the Universe. The Planck collaboration recently performed a stacking analysis of a large sample of `locally brightest galaxies' (LBGs) and, surprisingly, inferred an approximately self-similar relation between the tSZ flux and halo mass. At face value, this implies that the hot gas mass fraction is independent of halo mass, a result which is in apparent conflict with resolved X-ray observations. We test the robustness of the inferred trend using synthetic tSZ maps generated from cosmological hydrodynamical simulations and using the same tools and assumptions applied in the Planck study. We show that, while the detection and the estimate of the `total' flux (within $5 r_{500}$) is reasonably robust, the inferred flux originating from within $r_{500}$ (i.e. the limiting radius to which X-ray observations typically probe) is highly sensitive to the assumed pressure distribution of the gas. Using our most realistic simulations with AGN feedback, that reproduce a wide variety of X-ray and optical properties of groups and clusters, we estimate that the derived tSZ flux within $r_{500}$ is biased high by up to to an order of magnitude for haloes with masses $M_{500} \sim 10^{13}$ M$_{\odot}$. Moreover, we show that the AGN simulations are consistent with the total tSZ flux-mass relation observed with Planck, whereas a self-similar model is ruled out., Comment: 16 pages, 10 figures, MNRAS, accepted after minor revision

In this article we investigate the outer and inner mass distributions of the irregular galaxies UGC 4284 and UGC 11861, taking advantage of published HI and H{\alpha} high resolution rotation curves and constraining the stellar disk of both galaxies throughout stellar population synthesis studies. In addition we take into account the gas content of both galaxies deriving the HI+He rotation curve. The deduced baryonic rotation curves (star+gas) are inadequate to account for the total mass of UGC 4284 and UGC 11861, for that reason we examine the possibility of dark matter to explain the incongruity between the observed HI and H{\alpha} rotation curves of UGC 4284 and UGC 11861 and the derived baryonic rotation curves. We consider NFW, Burkert, DiCintio, Einasto, and the Stadel dark matter halos, to analyse the dark matter content of UGC 4284 and UGC 11861. The principal results of this work are that cored dark matter models better reproduce the dark matter H{\alpha} and HI rotation curves of UGC 11861 and the dark matter HI rotation curve of UGC 4284, while, the H{\alpha} rotation curve of UGC 4284 is better reproduced by a cuspy DiCintio DM model. In general, cored exponential two-parameters models Einasto and Stadel, give better fits than Burkert. This trend, as well as to confirm past results, presents for the first time a comparison between two different exponential dark matter models, Einasto and Stadel, in an attempt to better constrain the range of possible exponential dark matter models applied to real galaxies., Comment: Accepted for publication in MNRAS. 19 pages, 15 figures

We study the impact of relatively weak AGN feedback on the interstellar medium of intermediate and massive elliptical galaxies. We find that the AGN activity, while globally heating the ISM, naturally stimulates some degree of hot gas cooling on scales of several kpc. This process generates the persistent presence of a cold ISM phase, with mass ranging between 10$^4$ and $\gtrsim$ 5 $\times$ 10$^7$ M$_\odot$, where the latter value is appropriate for group centered, massive galaxies. Widespread cooling occurs where the ratio of cooling to free-fall time before the activation of the AGN feedback satisfies $t_{cool}/t_{ff} \lesssim 70$, that is we find a less restrictive threshold than commonly quoted in the literature. This process helps explaining the body of observations of cold gas (both ionized and neutral/molecular) in Ellipticals and, perhaps, the residual star formation detected in many early-type galaxies. The amount and distribution of the off-center cold gas vary irregularly with time. The cold ISM velocity field is irregular, initially sharing the (outflowing) turbulent hot gas motion. Typical velocity dispersions of the cold gas lie in the range 100-200 km/s. Freshly generated cold gas often forms a cold outflow and can appear kinematically misaligned with respect to the stars. We also follow the dust evolution in the hot and cold gas. We find that the internally generated cold ISM has a very low dust content, with representative values of the dust-to-gas ratio of 10$^{-4}$- 10$^{-5}$. Therefore, this cold gas can escape detection in the traditional dust-absorption maps., We better explained formulas in Section 2, to clarify the implementation of dust physics in the code. 23 pages, 12 figures. Published in MNRAS

A large number of high-redshift galaxies have been discovered via their narrow-band Lyα line or broad-band continuum colours in recent years. The nature of the escaping process of photons from these early galaxies is crucial to understand galaxy evolution and the cosmic reionization. Here, we investigate the escape of Lyα, non-ionizing UV-continuum (λ = 1300-1600 A in rest frame), and ionizing photons (λ < 912 A) from galaxies by combining a cosmological hydrodynamic simulation with three-dimensional multiwavelength radiative transfer calculations. The galaxies are simulated in a box of 5^3 h^−3 Mpc^3 with high resolutions using the Aquila initial condition which reproduces a Milky Way-like galaxy at redshift z = 0. We find that the escape fraction (f_esc) of these different photons shows a complex dependence on redshift and galaxy properties: $f_{\rm esc}^{\rm \rm {Ly{\alpha }}}$ and $f_{\rm esc}^{\rm UV}$ appear to evolve with redshift, and they show similar, weak correlations with galaxy properties such as mass, star formation, metallicity, and dust content, while $f_{\rm esc}^{\rm Ion}$ remains roughly constant at ∼0.2 from z ∼ 0 to 10, and it does not show clear dependence on galaxy properties. $f_{\rm esc}^{\rm \rm {Ly{\alpha }}}$ correlates more strongly with $f_{\rm esc}^{\rm UV}$ than with $f_{\rm esc}^{\rm Ion}$. In addition, we find a relation between the emergent Lyα luminosity and the ionizing photon emissivity of Lyman Alpha Emitters (LAEs). By combining this relation with the observed luminosity functions of LAEs at different redshift, we estimate the contribution from LAEs to the reionization of intergalactic medium (IGM). Our result suggests that ionizing photons from LAEs alone are not sufficient to ionize IGM at z ≳ 6, but they can maintain the ionization of IGM at z ∼ 0–5.

We study the baryonic, chemical and dynamical properties of a significantly large sample of early proto-galaxies in the first 500 Myr of the Universe (redshift z>9), obtained from high-resolution numerical, N-body, hydrodynamical, chemistry simulations including atomic and molecular networks, gas cooling, star formation, stellar evolution and metal spreading for population III and population II-I regimes according to proper stellar yields and lifetimes. We find that first star formation events take place in halos with dark-matter mass M_{DM} > 2\times 10^6 M_{sun}. Early star forming objects have: molecular fractions from x_{mol} < 10^{-4} in quiescent structures up to x_{mol} > 0.1 in active regions; star formation rates SFR ~10^{-8}-10^{-3}M_{sun}/yr; and metallicities in the range ~10^{-8}-10^{-2}Z_{sun}. Roughly ~10% of high-z haloes host population II-I star formation and dominate the cosmic SFR density. They usually are bursty objects with mean specific SFR around ~10 Gyr^{-1} at z~9 and increasing with redshift up to ~10^2 Gyr^{-1}. Stellar feedback effects alter the baryonic content of the haloes and locally affect their chemical and thermo-dynamical properties, as reflected by the broadening of various physical relations. The establishment of gaseous rotationally-supported cores is quite uncommon, weakly related to the large-scale dark-matter behaviour and evolving in an intermittent fashion. The colder, molecular-rich phase tends to maintain any established rotational motion longer with respect to the hotter, metal-rich component, which is very sensitive to environmental processes. While the fraction of haloes featuring a significant amount of co-rotating, molecular-rich gas increases with cosmic time (from a few percent at z~20 up to ~5-15% at z~9), the chaotic nature of metal-enriched material does not lead to particular trends., Comment: 20 pages, 19 figures; MNRAS, in press

We present a method for populating dark matter simulations with haloes of mass below the resolution limit. It is based on stochastically sampling a field derived from the density field of the halo catalogue, using constraints from the conditional halo mass function n(m|{\delta}). We test the accuracy of the method and show its application in the context of building mock galaxy samples. We find that this technique allows precise reproduction of the two-point statistics of galaxies in mock samples constructed with this method. Our results demonstrate that the full information content of a simulation can be communicated efficiently using only a catalogue of the more massive haloes., Comment: 6 pages, 4 figures, accepted for publication in MNRAS

One key piece of information missing from high redshift galaxy surveys is the galaxies' cold gas contents. We present a new method to indirectly determine cold gas surface densities and integrated gas masses from galaxy star formation rates and to separate the atomic and molecular gas components. Our predicted molecular and total gas surface densities and integrated masses are in very good agreement with direct measurements quoted in the literature for low and high-z galaxies. We apply this method to predict the gas content for a sample of $\sim 57000$ galaxies in the COSMOS field at $0.5 \leq z \leq 2.0$, selected to have $I_{AB} < 24$ mag. This approach allows us to investigate in detail the redshift evolution of galaxy cold and molecular gas content versus stellar mass and to provide fitting formulae for galaxy gas fractions. We find a clear trend between galaxy gas fraction, molecular gas fraction and stellar mass with redshift, suggesting that massive galaxies consume and/or expel their gas at higher redshift than less massive objects and have lower fractions of their gas in molecular form. The characteristic stellar mass separating gas- from stellar-dominated galaxies decreases with time. This indicates that massive galaxies reach a gas-poor state earlier than less massive objects. These trends can be considered to be another manifestation of downsizing in star formation activity.

We analyze the central dark-matter (DM) content of \sim 4,500 massive (M* \gsim 10^{10} Msun), low-redshift (z

The present paper extends to clusters of galaxies the study of Del Popolo (2012), concerning how the baryon-dark matter (DM) interplay shapes the density profile of dwarf galaxies. Cluster density profiles are determined taking into account dynamical friction, random and ordered angular momentum and the response of dark matter halos to condensation of baryons. We find that halos containing only DM are characterized by Einasto's profiles, and that the profile flattens with increasing content of baryons, and increasing values of random angular momentum. The analytical results obtained in the first part of the paper were applied to well studied clusters whose inner profiles have slopes flatter than NFW predictions (A611, A383) or are characterized by profiles in agreement with the NFW model (MACS J1423.8+2404, RXJ1133). By using independently-measured baryonic fraction, a typical spin parameter value $\lambda \simeq 0.03$, and adjusting the random angular momentum, we re-obtain the mass and density profiles of the quoted clusters. Finally, we show that the baryonic mass inside $\simeq 10$ kpc, $M_{b,in}$ is correlated with the total mass of the clusters, %finding a correlation among the two quantities, as $M_{b,in} \propto M_{500}^{0.4}$.

We report a study of the stellar content of the Near-infrared cluster [DBS2003]\,157 embedded in the extended H\,{\sc ii} region GAL\,331.31-00.34, which is associated with the IRAS source 16085-5138. $JHK$ photometry was carried out in order to identify potential ionizing candidates, and the follow-up NIR spectroscopy allowed the spectral classification of some sources, including two O-type stars. A combination of NIR photometry and spectroscopy data was used to obtain the distance of these two stars, with the method of spectroscopic parallax: IRS\,298 (O6\,{\sc V}, $3.35 \pm 0.61$\,kpc) and IRS\,339 (O9\,{\sc V}, $3.24 \pm 0.56$\,kpc). Adopting the average distance of $3.29 \pm 0.58$\,kpc and comparing the Lyman continuum luminosity of these stars with that required to account for the radio continuum flux of the H\,{\sc ii} region, we conclude that these two stars are the ionizing sources of GAL\,331.31-00.34. Young stellar objects (YSOs) were searched by using our NIR photometry and MIR data from the GLIMPSE survey. The analysis of NIR and MIR colour-colour diagrams resulted in 47 YSO candidates. The GLIMPSE counterpart of IRAS\,16085-5138, which presents IRAS colour indices compatible with an ultra-compact H\,{\sc ii} region, has been identified. The analysis of its spectral energy distribution between 2 and $100\,\mu$m revealed that this source shows a spectral index $\alpha = 3.6$ between 2 and $25\,\mu$m, which is typical of a YSO immersed in a protostellar envelope. Lower limits to the bolometric luminosity and the mass of the embedded protostar have been estimated as $L=7.7\times10^3L_{\sun}$ and $M = 10\,M_{\sun}$, respectively, which corresponds to a B0--B1\,{\sc V} ZAMS star.

We use Herschel-PACS far-infrared data, combined with previous multi-band information and mid-IR spectra, to properly account for the presence of an active nucleus and constrain its energetic contribution in luminous infrared (IR) sources at z\sim2. The sample is composed of 24 sources in the GOODS-South field, with typical IR luminosity of 10^{12} Lo. Data from the 4 Ms Chandra X-ray imaging in this field are also used to identify and characterize AGN emission. We reproduce the observed spectral energy distribution (SED), decomposed into a host-galaxy and an AGN component. A smooth-torus model for circum-nuclear dust is used to account for the direct and re-processed contribution from the AGN. We confirm that galaxies with typical L_{8-1000um}\sim10^{12}Lo at z\sim2 are powered predominantly by star-formation. An AGN component is present in nine objects (\sim35% of the sample) at the 3sigma confidence level, but its contribution to the 8-1000 um emission accounts for only \sim5% of the energy budget. The AGN contribution rises to \sim23% over the 5-30 um range (in agreement with Spitzer IRS results) and to \sim60% over the narrow 2-6 um range. The presence of an AGN is confirmed by X-ray data for 3 (out of nine) sources, with X-ray spectral analysis indicating the presence of significant absorption, i.e. NH\sim10^{23}-10^{24} cm^{-2}. An additional source shows indications of obscured AGN emission from X-ray data. The comparison between the mid-IR--derived X-ray luminosities and those obtained from X-ray data suggests that obscuration is likely present also in the remaining six sources that harbour an AGN according to the SED-fitting analysis.

We present a detailed analysis of two fields located 26 kpc (~5 scalelengths) from the centre of M31. One field samples the major axis populations--the Outer Disc field--while the other is offset by ~18' and samples the Warp in the stellar disc. The CMDs based on HST/ACS imaging reach old main-sequence turn-offs (~12.5 Gyr). We apply the CMD-fitting technique to the Warp field to reconstruct the star formation history (SFH). We find that after undergoing roughly constant SF until about 4.5 Gyr ago, there was a rapid decline in activity and then a ~1.5 Gyr lull, followed by a strong burst lasting 1.5 Gyr and responsible for 25% of the total stellar mass in this field. This burst appears to be accompanied by a decline in metallicity which could be a signature of the inflow of metal-poor gas. The onset of the burst (~3 Gyr ago) corresponds to the last close passage of M31 and M33 as predicted by detailed N-body modelling, and may have been triggered by this event. We reprocess the deep M33 outer disc field data of Barker et al. (2011) in order to compare consistently-derived SFHs. This reveals a similar duration burst that is exactly coeval with that seen in the M31 Warp field, lending further support to the interaction hypothesis. The complex SFHs and the smoothly-varying age-metallicity relations suggest that the stellar populations observed in the far outer discs of both galaxies have largely formed in situ rather than migrated from smaller galactocentric radii. The strong differential reddening affecting the CMD of the Outer Disc field prevents derivation of the SFH. Instead, we quantify this reddening and find that the fine-scale distribution of dust precisely follows that of the HI gas. This indicates that the outer HI disc of M31 contains a substantial amount of dust and therefore suggests significant metal enrichment in these parts, consistent with inferences from our CMD analysis.

We review the soft X-ray properties of 3C 390.3, 3C 120, 3C 382 and 3C 445, the only Broad Line Radio Galaxies (BLRG) for which good quality gratings data are currently available. The XMM-Newton/RGS data of 3C 390.3 and 3C 120 were re-analyzed searching for warm absorbers, already discovered in 3C 382 and 3C 445. We confirm the absence of ionized absorption features in 3C 120, but find signatures of outflowing gas (v_out \sim 10^2 km s^-1) in 3C 390.3. Its warm absorber (Log\xi \sim 2 erg cm s^-1, N_H\sim 10^20 cm^-2), similar to that observed in 3C 382, is probably placed in the Narrow Line Regions. Its gas content is slower and less dense than the accretion disk wind discovered in 3C 445. Independently from the location of the warm gas, the outflowing masses (\dotM_out) of BLRGs are significantly (but improbably) predominant with respect to the accretion masses (\dotM_acc), suggesting a clumpy configuration of the warm absorber. However, even assuming overestimated values of \dotM_out, the kinetic luminosity of the outflow (\dotE_out) is well below 1% of the kinetic power of the jet (P_jet). Thus, the jet remains the major driver of the radio-loud AGN feedback at least on pc scale and beyond. The warm absorber parameters (N_H, \xi) of BLRGs span similar range of values of type 1 radio-quiet AGNs. However, when the mass outflow rate of BLRGs and Seyfert 1s is plotted as a function of the radio-loudness, R=Log [\nu L_\nu(5GHz)/L_(2-10keV)], the mass outflow rate seems to increase with radio power.

We investigate the influence of dark energy on structure formation, within five different cosmological models, namely a concordance $\Lambda$CDM model, two models with dynamical dark energy, viewed as a quintessence scalar field (using a RP and a SUGRA potential form) and two extended quintessence models (EQp and EQn) where the quintessence scalar field interacts non-minimally with gravity (scalar-tensor theories). We adopted for all models the normalization of the matter power spectrum $\sigma_{8}$ to match the CMB data. In the models with dynamical dark energy and quintessence, we describe the equation of state with $w_0\approx-0.9$, still within the range allowed by observations. For each model, we have performed hydrodynamical simulations in a cosmological box of $(300 \ {\rm{Mpc}} \ h^{-1})^{3}$ including baryons and allowing for cooling and star formation. The contemporary presence of evolving dark energy and baryon physics allows us to investigate the interplay between the different background cosmology and the evolution of the luminous matter. Since cluster baryon fraction can be used to constrain other cosmological parameters such as $\Omega_{m}$, we also analyse how dark energy influences the baryon content of galaxy clusters. We find that, in models with dynamical dark energy, the evolving cosmological background leads to different star formation rates and different formation histories of galaxy clusters, but the baryon physics is not affected in a relevant way. We investigate several proxies of the cluster mass function based on X-ray observables like temperature, luminosity, $M_{gas}$, and $Y_{gas}$. We conclude that the X-ray temperature and $M_{gas}$ functions are better diagnostic to disentangle the growth of structures among different dark energy models. [Abridged]

An anomalous radio continuum component at cm-wavelengths has been observed in various sources, including dark clouds. This continuum component represents a new property of the ISM. In this work we focus on one particular dark cloud, the bright reflection nebula M 78. The main goal of this work is to invetigate cm-wave continuum emission in a prominent molecular cloud, nearby and with complementary observational data. We acquired Cosmic Background Imager (CBI) visibility data of M 78 at 31 GHz with an angular resolution of $\sim 5.8\arcmin$ and CBI2 data at an angular resolution of $\sim 4.2\arcmin$. A morphological analysis was undertaken to search for possible correlations with templates that trace different emission mechanisms. Using data from WMAP and the Rhodes/HartRAO 2326 MHz survey we constructed the spectral energy distribution (SED) of M 78 in a $45\arcmin$ circular aperture. We used results from the literature to constrain the physical conditions and the stellar content. The 5 GHz -- 31 GHz spectral index in flux density ($\alpha = 1.89\pm 0.15$) is significantly different from optically thin free-free values. We also find closer morphological agreement with IR dust tracers than with free-free sources. Dust-correlated cm-wave emission that is not due to free-free is significant at small scales ($\sim 8\arcmin$). However, a free-free background dominates at cm-wavelengths on large scales ($\sim 1$ deg). We correct for this uniform background by differencing against a set of reference fields. The differenced SED of M 78 shows excess emission at 10-70 GHz over free-free and a modified blackbody, at $3.4\sigma$. The excess is matched by the spinning dust model from Draine and Lazarian (1998).

We present a near infrared study of the stellar content of 35 H\,{\sc{ii}} regions in the Galactic plane. In this work, we have used the near infrared domain $J-$, $H-$ and $K_{s}-$ band color images to visually inspect the sample. Also, color-color and color-magnitude diagrams were used to indicate ionizing star candidates, as well as, the presence of young stellar objects such as classical TTauri Stars (CTTS) and massive young stellar objects (MYSOs). We have obtained {\it Spitzer} IRAC images for each region to help further characterize them. {\it Spitzer} and near infrared morphology to place each cluster in an evolutionary phase of development. {\it Spitzer} photometry was also used to classify the MYSOs. Comparison of the main sequence in color-magnitude diagrams to each observed cluster was used to infer whether or not the cluster kinematic distance is consistent with brightnesses of the stellar sources. We find qualitative agreement for a dozen of the regions, but about half the regions have near infrared photometry that suggests they may be closer than the kinematic distance. A significant fraction of these already have spectrophotometric parallaxes which support smaller distances. These discrepancies between kinematic and spectrophotometric distances are not due to the spectrophotometric methodologies, since independent non-kinematic measurements are in agreement with the spectrophotometric results. For instance, trigonometric parallaxes of star-forming regions were collected from the literature and show the same effect of smaller distances when compared to the kinematic results. In our sample of H\,{\sc{ii}} regions, most of the clusters are evident in the near infrared images. Finally, it is possible to distinguish among qualitative evolutionary stages for these objects.

We present wide area radio (12 mm) Mopra Telescope observations of the complex and rich massive star forming region G305. Our goals are to determine the reservoir for star formation within G305 using NH3 to trace the dense molecular content, and thus, the gas available to form stars; estimate physical parameters of detected NH3 clumps (temperature, column density, mass etc); locate current areas of active star formation via the presence of H2O and methanol masers and the distribution of YSOs and ultra compact HII regions associated with this region. This paper details the NH3 (J,K), (1,1), (2,2) and (3,3) inversion transition and 22 GHz H2O maser observations. We observed a \sim 1.5\circ x 1\circ region with \sim 2' angular resolution and a sensitivity of \sim 60 mK per 0.4 km s^-1 channel. We identify 15 NH3 (1,1), 12 NH3 (2,2) and 6 NH3 (3,3) clumps surrounding the central HII region. The sizes of the clumps vary between 10^4 M\odot and find the total molecular mass of the complex to be \sim 6x10^5 M\odot. We note the positions of 56 star formation tracers, and discover a high degree of correlation with detected NH3 clumps. We have detected 16 H2O masers, find they correlate with the detected ammonia clumps and in general are found closer to the NH3 clump cores than star formation tracers of later evolutionary stages.

We report the discovery of a new broad interstellar (or circumstellar) band at 7088.8 +- 2.0 \AA coincident to within the measurement uncertainties with the strongest band of the anthracene cation (C$_{14}$H$_{10}$$^+$) as measured in gas-phase laboratory spectroscopy at low temperatures (Sukhorukov et al.2004). The band is detected in the line of sight of star Cernis 52, a likely member of the very young star cluster IC 348, and is probably associated with cold absorbing material in a intervening molecular cloud of the Perseus star forming region where various experiments have recently detected anomalous microwave emission. From the measured intensity and available oscillator strength we find a column density of N$_{an^+}$= 1.1(+-0.4) x 10$^{13}$ cm$^{-2}$ implying that ~0.008% of the carbon in the cloud could be in the form of C$_{14}$H$_{10}$$^+$. A similar abundance has been recently claimed for the naphthalene cation (Iglesias-Groth et al. 2008) in this cloud. This is the first location outside the Solar System where specific PAHs are identified. We report observations of interstellar lines of CH and CH$^+$ that support a rather high column density for these species and for molecular hydrogen. The strength ratio of the two prominent diffuse interstellar bands at 5780 and 5797 \AA suggests the presence of a ``zeta'' type cloud in the line of sight (consistent with steep far-UV extinction and high molecular content). The presence of PAH cations and other related hydrogenated carbon molecules which are likely to occur in this type of clouds reinforce the suggestion that electric dipole radiation from fast spinning PAHs is responsible of the anomalous microwave emission detected toward Perseus.

We have obtained deep near-infrared $J$- (1.25 $\mu$m), $H$- (1.65$ \mu$m) and $K_s$-band (2.15 $\mu$m) imaging for a sample of six dwarf galaxies ($M_B\ga-17$ mag) in the Local Volume (LV, $D\la10$ Mpc). The sample consists mainly of early-type dwarf galaxies found in various environments in the LV. Two galaxies (LEDA 166099 and UGCA 200) in the sample are detected in the near-infrared for the first time. The deep near-infrared images allow for a detailed study of the photometric and structural properties of each galaxy. The surface brightness profiles of the galaxies are detected down to the ~$24 mag arcsec^{-2}$ isophote in the $J$- and $H$-bands, and $23 mag arcsec^{-2}$ in the $K_s$-band. The total magnitudes of the galaxies are derived in the three wavelength bands. For the brightest galaxies ($M_B\la-15.5$ mag) in the sample, we find that the Two Micron All Sky Survey (2MASS) underestimates the total magnitudes of these systems by up to $\la0.5$ mag. The radial surface brightness profiles of the galaxies are fitted with an exponential (for those galaxies having a stellar disk) or Sersic law to derive the structure of the underlying stellar component. In particular, the effective surface brightness ($\mu_e$) and effective radius ($r_e$) are determined from the analytic fits to the surface brightness profile. The $J$-$K_s$ colours for the galaxies have been measured to explore the luminosity-metallicity relation for early-type dwarfs. In addition, the $B$-$K_s$ colours of the galaxies are used to assess their evolutionary state relative to other galaxy morphologies. The total stellar masses of the dwarf galaxies are derived from the $H$-band photometric measurements. These will later be compared to the dynamical mass estimates for the galaxies to determine their dark matter content.

We present a quantitative estimate of the relative AGN/starburst content in a sample of 59 nearby (z85% of the observed infrared luminosity. The subsample of sources optically classified as LINERs (31 objects) shows a similar AGN/starburst distribution as the whole sample, indicating a composite nature for this class of objects. We also show that a few ULIRGs, optically classified as starbursts, have L-band spectral features suggesting the presence of a buried AGN., 8 Pages, 5 figures. Accepted for publication in MNRAS