Search

We present a study of the molecular gas in five closely-spaced ($R_{\perp}<20$ kpc) dual quasars ($L_{\rm bol}\gtrsim10^{44}~\mathrm{erg~s}^{-1}$) at redshifts $0.4

Travel to academic conferences -- where international flights are the norm -- is responsible for a sizeable fraction of the greenhouse gas (GHG) emissions associated with academic work. In order to provide a benchmark for comparison with other fields, as well as for future reduction strategies and assessments, we estimate the CO2-equivalent emissions for conference travel in the field of astronomy for the prepandemic year 2019. The GHG emission of the international astronomical community's 362 conferences and schools in 2019 amounted to 42,500 tCO2e, assuming a radiative-forcing index factor of 1.95 for air travel. This equates to an average of 1.0 $\pm$ 0.6 tCO2e per participant per meeting. The total travel distance adds up to roughly 1.5 Astronomical Units, that is, 1.5 times the distance between the Earth and the Sun. We present scenarios for the reduction of this value, for instance with virtual conferencing or hub models, while still prioritizing the benefits conferences bring to the scientific community., Comment: Supplementary material is available at PNAS Nexus online: https://academic.oup.com/pnasnexus/article/3/5/pgae143/7659884

JWST is revealing a new remarkable population of high-redshift ($z\gtrsim4$), low-luminosity Active Galactic Nuclei (AGNs) in deep surveys and detecting the host galaxy stellar light in the most luminous and massive quasars at $z\sim 6$ for the first time. Latest results claim supermassive black holes (SMBHs) in these systems to be significantly more massive than expected from the local BH mass - stellar mass ($\mathcal{M}_{\rm BH} - \mathcal{M}_\star$) relation and that this is not due to sample selection effects. Through detailed statistical modeling, we demonstrate that the coupled effects of selection biases (i.e., finite detection limit and requirements on detecting broad lines) and measurement uncertainties in $\mathcal{M}_{\rm BH}$ and $\mathcal{M}_\star$ can in fact largely account for the reported offset and flattening in the observed $\mathcal{M}_{\rm BH} - \mathcal{M}_\star$ relation toward the upper envelope of the local relation, even for those at $\mathcal{M}_{\rm BH} < 10^8\,M_{\odot}$. We further investigate the possible evolution of the $\mathcal{M}_{\rm BH} - \mathcal{M}_\star$ relation at $z\gtrsim 4$ with careful treatment of observational biases and consideration of the degeneracy between intrinsic evolution and dispersion in this relation. The bias-corrected intrinsic $\mathcal{M}_{\rm BH} - \mathcal{M}_\star$ relation in the low-mass regime suggests that there might be a large population of low-mass BHs (${\rm log}\,\mathcal{M}_{\rm BH} \lesssim 5$), possibly originating from lighter seeds, remaining undetected or unidentified even in the deepest JWST surveys. These results have important consequences for JWST studies of BH seeding and the coevolution between SMBHs and their host galaxies at the earliest cosmic times., Comment: 21 pages, 9 figures, submitted to ApJ

Our knowledge of relations between supermassive black holes and their host galaxies at $z\gtrsim1$ is still limited, even though being actively sought out to $z\sim6$. Here, we use the high resolution and sensitivity of JWST to measure the host galaxy properties for 61 X-ray-selected type-I AGNs at $0.7

We report the identification of 64 new candidates of compact galaxies, potentially hosting faint quasars with bolometric luminosities of $L_\mathrm{bol} = 10^{43}$--10$^{46}$ erg s$^{-1}$, residing in the reionization epoch within the redshift range of $6 \lesssim z \lesssim 8$. These candidates were selected by harnessing the rich multiband datasets provided by the emerging JWST-driven extragalactic surveys, focusing on COSMOS-Web, as well as JADES, UNCOVER, CEERS, and PRIMER. Our search strategy includes two stages: applying stringent photometric cuts to catalog-level data and detailed spectral energy distribution fitting. These techniques effectively isolate the quasar candidates while mitigating contamination from low-redshift interlopers, such as brown dwarfs and nearby galaxies. The selected candidates indicate physical traits compatible with low-luminosity active galactic nuclei, likely hosting $\approx10^5$--$10^7~M_\odot$ supermassive black holes (SMBHs) living in galaxies with stellar masses of $\approx10^8$--$10^{10}~M_\odot$. The SMBHs selected in this study, on average, exhibit an elevated mass compared to their hosts, with the mass ratio distribution slightly higher than those of galaxies in the local Universe. As with other high-$z$ studies, this is at least in part due to the selection method for these quasars. An extensive Monte Carlo analysis provides compelling evidence that heavy black hole seeds from the direct collapse scenario appear to be the preferred pathway to mature this specific subset of SMBHs by $z\approx7$. This work underscores the significance of further spectroscopic observations, as the quasar candidates presented here offer exceptional opportunities to delve into the nature of the earliest galaxies and SMBHs that formed during cosmic infancy., Comment: Accepted for publication in the Astronomy & Astrophysics journal. 19 pages, 10 figures, and 4 tables. We welcome comments from the reader

In this letter, we report the discovery of the highest redshift, heavily obscured, radio-loud AGN candidate selected using JWST NIRCam/MIRI, mid-IR, sub-mm, and radio imaging in the COSMOS-Web field. Using multi-frequency radio observations and mid-IR photometry, we identify a powerful, radio-loud (RL), growing supermassive black hole (SMBH) with significant spectral steepening of the radio SED ($f_{1.28 \mathrm{GHz}} \sim 2$ mJy, $q_{24\mu m} = -1.1$, $\alpha_{1.28-3\mathrm{GHz}}=-1.2$, $\Delta \alpha = -0.4$). In conjunction with ALMA, deep ground-based observations, ancillary space-based data, and the unprecedented resolution and sensitivity of JWST, we find no evidence of AGN contribution to the UV/optical/NIR data and thus infer heavy amounts of obscuration (N$_{\mathrm{H}} > 10^{23}$ cm$^{-2}$). Using the wealth of deep UV to sub-mm photometric data, we report a singular solution photo-z of $z_\mathrm{phot}$ = 7.7$^{+0.4}_{-0.3}$ and estimate an extremely massive host-galaxy ($\log M_{\star} = 11.4 -12\,\mathrm{M}_{\odot}$) hosting a powerful, growing SMBH (L$_{\mathrm{Bol}} = 4-12 \times 10^{46}$ erg s$^{-1}$). This source represents the furthest known obscured RL AGN candidate, and its level of obscuration aligns with the most representative but observationally scarce population of AGN at these epochs., Comment: Accepted to ApJL

A large fraction of the accreting supermassive black hole population is shrouded by copious amounts of gas and dust, particularly in the distant ($z\gtrsim1$) Universe. While much of the obscuration is attributed to a parsec-scale torus, there is a known contribution from the larger-scale host galaxy. Using JWST/NIRCam imaging from the COSMOS-Web survey, we probe the galaxy-wide dust distribution in X-ray selected AGN up to $z\sim2$. Here, we focus on a sample of three AGNs with their host galaxies exhibiting prominent dust lanes, potentially due to their edge-on alignment. These represent 27% (3 out of 11 with early NIRCam data) of the heavily obscured ($N_H>10^{23}$ cm$^{-2}$) AGN population. With limited signs of a central AGN in the optical and near-infrared, the NIRCam images are used to produce reddening maps $E(B-V)$ of the host galaxies. We compare the mean central value of $E(B-V)$ to the X-ray obscuring column density along the line-of-sight to the AGN ($N_H\sim10^{23-23.5}$ cm$^{-2}$). We find that the extinction due to the host galaxy is present ($0.6\lesssim E(B-V) \lesssim 0.9$; $1.9 \lesssim A_V \lesssim 2.8$) and significantly contributes to the X-ray obscuration at a level of $N_H\sim10^{22.5}$ cm$^{-2}$ assuming an SMC gas-to-dust ratio which amounts to $\lesssim$30% of the total obscuring column density. These early results, including three additional cases from CEERS, demonstrate the ability to resolve such dust structures with JWST and separate the different circumnuclear and galaxy-scale obscuring structures., Comment: 12 pages, 8 figures, Accepted for publication in ApJL

Over the last two decades, around 300 quasars have been discovered at $z\gtrsim6$, yet only one has identified as being strongly gravitationally lensed. We explore a new approach -- enlarging the permitted spectral parameter space, while introducing a new spatial geometry veto criterion -- which is implemented via image-based deep learning. We first apply this approach to a systematic search for reionization-era lensed quasars, using data from the Dark Energy Survey, the Visible and Infrared Survey Telescope for Astronomy Hemisphere Survey, and the Wide-field Infrared Survey Explorer.Our search method consists of two main parts: (i) the preselection of the candidates based on their spectral energy distributions (SEDs) using catalog-level photometry and (ii) relative probabilities calculation of the candidates being a lens or some contaminant, utilizing a convolutional neural network (CNN) classification. The training data sets are constructed by painting deflected point-source lights over actual galaxy images, to generate realistic galaxy-quasar lens models, optimized to find systems with small image separations, i.e., Einstein radii of $\theta_\mathrm{E} \leq 1$ arcsec. Visual inspection is then performed for sources with CNN scores of $P_\mathrm{lens} > 0.1$, which leads us to obtain 36 newly selected lens candidates, which are awaiting spectroscopic confirmation. These findings show that automated SED modeling and deep learning pipelines, supported by modest human input, are a promising route for detecting strong lenses from large catalogs that can overcome the veto limitations of primarily dropout-based SED selection approaches., Comment: 24 pages, 17 figures, and 2 tables. Accepted for publication in The Astrophysical Journal. We welcome comments from the reader

The detection of starlight from the host galaxies of quasars during the reionization epoch ($z>6$) has been elusive, even with deep HST observations. The current highest redshift quasar host detected, at $z=4.5$, required the magnifying effect of a foreground lensing galaxy. Low-luminosity quasars from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) mitigate the challenge of detecting their underlying, previously-undetected host galaxies. Here we report rest-frame optical images and spectroscopy of two HSC-SSP quasars at $z>6$ with JWST. Using NIRCam imaging at 3.6$\mu$m and 1.5$\mu$m and subtracting the light from the unresolved quasars, we find that the host galaxies are massive (stellar masses of $13\times$ and $3.4\times$ $10^{10}$ M$_{\odot}$, respectively), compact, and disk-like. NIRSpec medium-resolution spectroscopy shows stellar absorption lines in the more massive quasar, confirming the detection of the host. Velocity-broadened gas in the vicinity of these quasars enables measurements of their black hole masses ($1.4\times 10^9$ and $2.0\times$ $10^{8}$ M$_{\odot}$, respectively). Their location in the black hole mass - stellar mass plane is consistent with the distribution at low redshift, suggesting that the relation between black holes and their host galaxies was already in place less than a billion years after the Big Bang., Comment: Matched to the published Nature version of the article. 27 pages, 4 main figures, 1 table, 6 supplementary figures, 2 supplementary table

We present the survey design, implementation, and outlook for COSMOS-Web, a 255 hour treasury program conducted by the James Webb Space Telescope in its first cycle of observations. COSMOS-Web is a contiguous 0.54 deg$^2$ NIRCam imaging survey in four filters (F115W, F150W, F277W, and F444W) that will reach 5$\sigma$ point source depths ranging $\sim$27.5-28.2 magnitudes. In parallel, we will obtain 0.19 deg$^2$ of MIRI imaging in one filter (F770W) reaching 5$\sigma$ point source depths of $\sim$25.3-26.0 magnitudes. COSMOS-Web will build on the rich heritage of multiwavelength observations and data products available in the COSMOS field. The design of COSMOS-Web is motivated by three primary science goals: (1) to discover thousands of galaxies in the Epoch of Reionization ($64$ and place constraints on the formation of the Universe's most massive galaxies ($M_\star>10^{10}$\,M$_\odot$), and (3) directly measure the evolution of the stellar mass to halo mass relation using weak gravitational lensing out to $z\sim2.5$ and measure its variance with galaxies' star formation histories and morphologies. In addition, we anticipate COSMOS-Web's legacy value to reach far beyond these scientific goals, touching many other areas of astrophysics, such as the identification of the first direct collapse black hole candidates, ultracool sub-dwarf stars in the Galactic halo, and possibly the identification of $z>10$ pair-instability supernovae. In this paper we provide an overview of the survey's key measurements, specifications, goals, and prospects for new discovery., Comment: 46 pages, 16 figures, ApJ accepted

The interaction between Active Galactic Nuclei (AGN) and their host galaxies is scarcely resolved. Narrow-line Seyfert 1 (NLS1) galaxies are believed to represent AGN at early stages of their evolution and allow to observe AGN feeding and feedback processes at high accretion rates. We apply a spectroastrometric analysis to VLT MUSE NFM-AO observations of Mrk 1044, a nearby super-Eddington accreting NLS1. This allows us to map two ionised gas outflows traced by [O$\,$III] which have velocities of $-560\pm20\,{\rm km\:s}^{-1}$ and $-144 \pm 5 \,{\rm km\:s}^{-1}$. Both outflows are spatially unresolved and located close to the galaxy nucleus ($<1\,{\rm pc}$). They have gas densities higher than $10^5\,{\rm cm}^{-3}$, which implies that the BPT diagnostic cannot be used to constrain the underlying ionisation mechanism. We explore whether an expanding shell model can describe the velocity structure of Mrk 1044's unresolved multi-phase outflow. A kinematic analysis suggests that significant turbulence may be present in the ISM around the nucleus, which may lead to a condensation rain, potentially explaining the efficient feeding of Mrk 1044's AGN. We identify an additional ionised gas outflowing component that is spatially resolved. It has a velocity of $-211 \pm 22 \,{\rm km\:s}^{-1}$ and a projected size of $4.6 \pm 0.6 \,{\rm pc}$. Within the innermost 0.5" (160$\,{\rm pc}$) around the nucleus we detect modest star formation hidden by the beam-smeared emission from the outflow, which suggests that Mrk 1044's AGN phase set on recently. We estimate that the multi-phase outflow has been launched $<10^4 \,{\rm yrs}$ ago. It carries enough mass and energy to impact the host galaxy star formation on different spatial scales, highlighting the complexity of the AGN feeding and feedback cycle in its early stages., Comment: 17 pages. 12 figures. Re-submitted to A&A after minor revision. Comments welcome

We characterize the Ly$\alpha$ halo and absorption systems toward PSO J083+11, a unique $z=6.3401$ weak-line quasar, using Gemini/GNIRS, Magellan/FIRE, and VLT/MUSE data. Strong absorptions by hydrogen and several metal lines (e.g., CII, MgII, and OI) are discovered in the spectrum, which indicates the presence of: (i) a proximate sub-damped Ly$\alpha$ (sub-DLA) system at $z=6.314$ and (ii) a MgII absorber at $z=2.2305$. To describe the observed damping wing signal, we model the Ly$\alpha$ absorption with a combination of a sub-DLA with the neutral hydrogen column density of $\log N_\mathrm{HI} = 20.03 \pm 0.30$ cm$^{-2}$ and absorption from the intergalactic medium with a neutral fraction of around 10 percent. The sub-DLA toward PSO J083+11 has an abundance ratio of [C/O] $=-0.04 \pm 0.33$ and metallicity of [O/H] $=-2.19 \pm 0.44$, similar to those of low-redshift metal-poor DLAs. These measurements suggest that the sub-DLA might truncate PSO J083+11's proximity zone size and complicate the quasar lifetime measurement. However, this quasar shows no sign of a Ly$\alpha$ halo in the MUSE data cube, where the estimated $1\sigma$ limit of surface brightness is $2.76 \times 10^{-18}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$ at aperture size of 1 arcsecond, or equivalent to a Ly$\alpha$ luminosity of $\leq 43.46$ erg s$^{-1}$. This non-detection, while being only weak independent evidence on its own, is at least consistent with a young quasar scenario, as expected for a quasar with a short accretion timescale., Comment: 22 pages, 12 figures, and 1 table. Replaced to match version accepted for publication in The Astronomical Journal. We welcome the comments from the reader. Related paper: arXiv:2009.07784

The James Webb Space Telescope will have the power to characterize high-redshift quasars at z>6 with an unprecedented depth and spatial resolution. While the brightest quasars at such redshift (i.e., with bolometric luminosity L_bol> 10^46 erg/s) provide us with key information on the most extreme objects in the Universe, measuring the black hole (BH) mass and Eddington ratios of fainter quasars with L_bol= 10^45-10^46 erg/s opens a path to understand the build-up of more normal BHs at z>6. In this paper, we show that the Illustris, TNG100, TNG300, Horizon-AGN, EAGLE, and SIMBA large-scale cosmological simulations do not agree on whether BHs at z>4 are overmassive or undermassive at fixed galaxy stellar mass with respect to the M_BH-M_star scaling relation at z=0 (BH mass offsets). Our conclusions are unchanged when using the local scaling relation produced by each simulation or empirical relations. We find that the BH mass offsets of the simulated faint quasar population at z>4, unlike those of bright quasars, represent the BH mass offsets of the entire BH population, for all the simulations. Thus, a population of faint quasars with L_bol= 10^45-10^46 erg/s observed by JWST can provide key constraints on the assembly of BHs at high redshift. Moreover, this will help constraining the high-redshift regime of cosmological simulations, including BH seeding, early growth, and co-evolution with the host galaxies. Our results also motivate the need for simulations of larger cosmological volumes down to z=6, with the same diversity of sub-grid physics, in order to gain statistics on the most extreme objects at high redshift., Comment: published in MNRAS, 19 pages, 8 figures, key figures: Fig. 3, Fig.5, and Fig. 7

We present a method of selecting quasars up to redshift $\approx$ 6 with random forests, a supervised machine learning method, applied to Pan-STARRS1 and WISE data. We find that, thanks to the increasing set of known quasars we can assemble a training set that enables supervised machine learning algorithms to become a competitive alternative to other methods up to this redshift. We present a candidate set for the redshift range 4.8 to 6.3 which includes the region around z = 5.5 where quasars are difficult to select due to photometric similarity to red and brown dwarfs. We demonstrate that under our survey restrictions we can reach a high completeness ($66 \pm 7 \%$ below redshift 5.6 / $83^{+6}_{-9}\%$ above redshift 5.6) while maintaining a high selection efficiency ($78^{+10}_{-8}\%$ / $94^{+5}_{-8}\%$). Our selection efficiency is estimated via a novel method based on the different distributions of quasars and contaminants on the sky. The final catalog of 515 candidates includes 225 known quasars. We predict the candidate catalog to contain an additional $148^{+41}_{-33}$ new quasars below redshift 5.6 and $45^{+5}_{-8}$ above and make the catalog publicly available. Spectroscopic follow-up observations of 37 candidates lead us to discover 20 new high redshift quasars (18 at $4.6\le z\le5.5$, 2 $z\sim5.7$). These observations are consistent with our predictions on efficiency. We argue that random forests can lead to higher completeness because our candidate set contains a number of objects that would be rejected by common color cuts, including one of the newly discovered redshift 5.7 quasars., Comment: Accepted by AJ

The annual meeting of the European Astronomical Society took place in Lyon, France, in 2019, but in 2020 it was held online only due the COVID-19 pandemic. The carbon footprint of the virtual meeting was roughly 3,000 times smaller than the face-to-face one, providing encouragement for more ecologically minded conferencing., Comment: Originated in a Twitter discussion (https://twitter.com/sarahkendrew/status/1144186571538739202) at EWASS 2019; followed up at the EAS 2020 conference sustainability session by https://astronomersforplanet.earth - published in Nature Astronomy, September 2020

Analysing greenhouse gas emissions of an astronomical institute is a first step in reducing its environmental impact. Here, we break down the emissions of the Max Planck Institute for Astronomy in Heidelberg and propose measures for reductions., Comment: Originated at EAS 2020 conference, sustainability session by https://astronomersforplanet.earth - published in Nature Astronomy, September 2020

We present the discovery of PSO J083.8371+11.8482, a weak emission line quasar with extreme star formation rate at $z=6.3401$. This quasar was selected from Pan-STARRS1, UHS, and unWISE photometric data. Gemini/GNIRS spectroscopy follow-up indicates a MgII-based black hole mass of $M_\mathrm{BH}=\left(2.0^{+0.7}_{-0.4}\right)\times10^9~M_\odot$ and an Eddington ratio of $L_\mathrm{bol}/L_\mathrm{Edd}=0.5^{+0.1}_{-0.2}$, in line with actively accreting supermassive black hole (SMBH) at $z\gtrsim6$. HST imaging sets strong constraint on lens-boosting, showing no relevant effect on the apparent emission. The quasar is also observed as a pure point-source with no additional emission component. The broad line region (BLR) emission is intrinsically weak and not likely caused by an intervening absorber. We found rest-frame equivalent widths of EW(Ly$\alpha$+NV) $=5.7\pm0.7$ Angstrom, EW(CIV) $\leq5.8$ Angstrom (3-sigma upper limit), and EW(MgII) $=8.7\pm0.7$ Angstrom. A small proximity zone size ($R_\mathrm{p}=1.2\pm0.4$ pMpc) indicates a lifetime of only $t_\mathrm{Q}=10^{3.4\pm0.7}$ years from the last quasar phase ignition. ALMA shows extended [CII] emission with a mild velocity gradient. The inferred far-infrared luminosity ($L_\mathrm{FIR}=(1.2\pm0.1)\times10^{13}\,L_\odot$) is one of the highest among all known quasar hosts at $z\gtrsim6$. Dust and [CII] emissions put a constraint on the star formation rate of SFR $=900-4900~M_\odot\,\mathrm{yr^{-1}}$, similar to that of hyper-luminous infrared galaxy. Considering the observed quasar lifetime and BLR formation timescale, the weak-line profile in the quasar spectrum is most likely caused by a BLR which is not yet fully formed rather than continuum boosting by gravitational lensing or a soft continuum due to super-Eddington accretion., Comment: 28 pages, 16 figures, 3 tables, accepted for publication in ApJ

We report on a Hubble Space Telescope search for rest-frame ultraviolet emission from the host galaxies of five far-infrared-luminous $z\simeq{}6$ quasars and the $z=5.85$ hot-dust free quasar SDSS J0005-0006. We perform 2D surface brightness modeling for each quasar using a Markov-Chain Monte-Carlo estimator, to simultaneously fit and subtract the quasar point source in order to constrain the underlying host galaxy emission. We measure upper limits for the quasar host galaxies of $m_J>22.7$ mag and $m_H>22.4$ mag, corresponding to stellar masses of $M_\ast<2\times10^{11}M_\odot$. These stellar mass limits are consistent with the local $M_{\textrm{BH}}$-$M_\ast$ relation. Our flux limits are consistent with those predicted for the UV stellar populations of $z\simeq6$ host galaxies, but likely in the presence of significant dust ($\langle A_{\mathrm{UV}}\rangle\simeq 2.6$ mag). We also detect a total of up to 9 potential $z\simeq6$ quasar companion galaxies surrounding five of the six quasars, separated from the quasars by 1.4''-3.2'', or 8.4-19.4 kpc, which may be interacting with the quasar hosts. These nearby companion galaxies have UV absolute magnitudes of -22.1 to -19.9 mag, and UV spectral slopes $\beta$ of -2.0 to -0.2, consistent with luminous star-forming galaxies at $z\simeq6$. These results suggest that the quasars are in dense environments typical of luminous $z\simeq6$ galaxies. However, we cannot rule out the possibility that some of these companions are foreground interlopers. Infrared observations with the James Webb Space Telescope will be needed to detect the $z\simeq6$ quasar host galaxies and better constrain their stellar mass and dust content., Comment: 22 pages, 13 figures. Accepted for publication in ApJ

The unique combination of superb spatial resolution, wide-area coverage, and deep depth of the optical imaging from the Hyper Suprime-Cam (HSC) Subaru Strategic Program is utilized to search for dual quasar candidates. Using an automated image analysis routine on 34,476 known SDSS quasars, we identify those with two (or more) distinct optical point sources in HSC images covering 796 deg^2. We find 421 candidates out to a redshift of 4.5 of which one hundred or so are more likely after filtering out contaminating stars. Angular separations of 0.6 - 4.0" correspond to projected separations of 3 - 30 kpc, a range relatively unexplored for population studies of luminous dual quasars. Using Keck-I/LRIS and Gemini-N/NIFS, we spectroscopically confirm three dual quasar systems at z < 1, two of which are previously unknown out of eight observed, based on the presence of characteristic broad emission lines in each component, while highlighting that the continuum of one object in one of the pairs is reddened. In all cases, the [OIII]5007 emission lines have mild velocity offsets, thus the joint [OIII] line profile is not double-peaked. We find a dual quasar fraction of 0.26+/-0.18% and no evidence for evolution. A comparison with the Horizon-AGN simulation seems to support the case of no evolution in the dual quasar fraction when broadly matching the quasar selection. These results may indicate a scenario in which the frequency of the simultaneous triggering of luminous quasars is not as sensitive as expected to the cosmic evolution of the merger rate or gas content of galaxies., Comment: 11 pages; 12 figures; Accepted for publication in The Astrophysical Journal

We present deep (9 hours) Gemini-N/GNIRS near-infrared spectroscopic observations of ULAS J1342+0928, a luminous quasar at z=7.54. Various broad emission lines were detected, as well as the underlying continuum and iron forests over the rest-frame wavelength 970-2930A. There is a clear trend that higher-ionization emission lines show larger blueshifts with CIV1549 exhibiting 5510^{+240}_{-110} km s-1 blueshift with respect to the systematic redshift from the far-infrared [CII] 158um emission line. Those high ionization lines have wide profiles with FWHM more than 10000 km s-1. A modest blueshift of 340^{+110}_{-80} km s-1 is also seen in MgII, the lowest ionization line identified in the spectrum. The updated MgII-based black hole mass of M_BH=9.1_{-1.3}^{+1.4} x 10^8 M_sun and the Eddington ratio of L_bol/L_Edd=1.1_{-0.2}^{+0.2} confirm that ULAS J1342+0928 is powered by a massive and actively accreting black hole. There is no significant difference in the emission line ratios such as SiIV/CIV and AlIII/CIV when compared to lower-redshift quasars in a similar luminosity range, which suggests early metal pollution of the broad-line-region clouds. This trend also holds for the FeII/MgII line ratio, known as a cosmic clock that traces the iron enrichment in the early universe. Different iron templates and continuum fitting ranges were used to explore how the FeII/MgII measurement changes as a function of spectral modeling. Quasars at even higher redshift or at fainter luminosity range (L_bol<10^46 erg s-1) are needed to probe the sites of early metal enrichment and a corresponding change in the FeII/MgII ratio., Comment: 21 pages, 8 figures, 3 tables, accepted for publication in ApJ

A series of gravitational instabilities in a circumnuclear gas disk (CND) are required to trigger gas transport to a central supermassive black hole (SMBH) and ignite Active Galactic Nuclei (AGNs). A test of this scenario is to investigate whether an enhanced molecular gas mass surface density ($\Sigma_{\rm mol}$) is found in the CND-scale of quasars relative to a comparison sample of inactive galaxies. Here we performed sub-kpc resolution CO(2-1) observations with ALMA of four low-redshift ($z \sim 0.06$), luminous ($\sim 10^{45}$ erg s$^{-1}$) quasars with each matched to a different star-forming galaxy, having similar redshift, stellar mass, and star-formation rate. We detected CO(2-1) emission from all quasars, which show diverse morphologies. Contrary to expectations, $\Sigma_{\rm mol}$ of the quasar sample, computed from the CO(2-1) luminosity, tends to be smaller than the comparison sample at $r < 500$ pc; there is no systematic enhancement of $\Sigma_{\rm mol}$ in our quasars. We discuss four possible scenarios that would explain the lower molecular gas content (or CO(2-1) luminosity as an actual observable) at the CND-scale of quasars, i.e., AGN-driven outflows, gas-rich minor mergers, time-delay between the onsets of a starburst-phase and a quasar-phase, and X-ray-dominated region (XDR) effects on the gas chemical abundance and excitation. While not extensively discussed in the literature, XDR effects can have an impact on molecular mass measurements particularly in the vicinity of luminous quasar nuclei; therefore higher resolution molecular gas observations, which are now viable using ALMA, need to be considered., Comment: 17 pages, 8 figures, 4 tables (including 1 table and 1 figure in the appendix). Accepted for publication in ApJ; Minor updates after the acceptance

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument., Comment: Full report: 498 pages. Executive Summary: 14 pages. More information about HabEx can be found here: https://www.jpl.nasa.gov/habex/

The evolution of the galaxy size - stellar mass (Mstellar) relation has been a puzzle for over a decade. High redshift galaxies are significantly more compact than galaxies observed today, at an equivalent mass, but how much of this apparent growth is driven by progenitor bias, minor mergers, secular processes, or feedback from AGN is unclear. To help disentangle the physical mechanisms at work by addressing the latter, we study the galaxy size - Mstellar relation of 32 carefully-selected broad-line AGN hosts at 1.2 < z < 1.7 (7.5 < log M_BH < 8.5; L_bol/L_Edd > 0.1). Using HST with multi-band photometry and state-of-the-art modeling techniques, we measure half-light radii while accounting for uncertainties from subtracting bright central point sources. We find AGN hosts to have sizes ranging from 1 to 6 kpc at Mstellar ~ 0.3 - 1 x 10^11 Msun. Thus, many hosts have intermediate sizes as compared to equal-mass star-forming and quiescent galaxies. While inconsistent with the idea that AGN feedback may induce an increase in galaxy sizes, this finding is consistent with hypotheses in which AGNs preferentially occur in systems with prior concentrated gas reservoirs, or are involved in secular compaction processes perhaps responsible for simultaneously building bulges and shutting down star formation. If driven by minor mergers, which do not grow central black holes as fast as they do bulge-like stellar structures, such a process would explain both the galaxy size - mass relation observed here and the evolution in the black hole, bulge mass relation described in a companion paper., Comment: 4 pages; 1 figure; To be resubmitted to ApJ Letters imminently; minor corrections based on comments from the referee have been included; Further comments are welcome

Correlations between the mass of a supermassive black hole and the properties of its host galaxy (e.g., total stellar mass (M*), luminosity (Lhost)) suggest an evolutionary connection. A powerful test of a co-evolution scenario is to measure the relations MBH-Lhost and MBH-M* at high redshift and compare with local estimates. For this purpose, we acquired HST imaging with WFC3 of 32 X-ray-selected broad-line AGN at 1.2

Euclid is a space-based optical/near-infrared survey mission of the European Space Agency (ESA) to investigate the nature of dark energy, dark matter and gravity by observing the geometry of the Universe and on the formation of structures over cosmological timescales. Euclid will use two probes of the signature of dark matter and energy: Weak gravitational Lensing, which requires the measurement of the shape and photometric redshifts of distant galaxies, and Galaxy Clustering, based on the measurement of the 3-dimensional distribution of galaxies through their spectroscopic redshifts. The mission is scheduled for launch in 2020 and is designed for 6 years of nominal survey operations. The Euclid Spacecraft is composed of a Service Module and a Payload Module. The Service Module comprises all the conventional spacecraft subsystems, the instruments warm electronics units, the sun shield and the solar arrays. In particular the Service Module provides the extremely challenging pointing accuracy required by the scientific objectives. The Payload Module consists of a 1.2 m three-mirror Korsch type telescope and of two instruments, the visible imager and the near-infrared spectro-photometer, both covering a large common field-of-view enabling to survey more than 35% of the entire sky. All sensor data are downlinked using K-band transmission and processed by a dedicated ground segment for science data processing. The Euclid data and catalogues will be made available to the public at the ESA Science Data Centre., Comment: 23 pages, 19 figures, Presented at the SPIE Astronomical Telescopes and Instrumentation conference in Edinburgh, Scotland, United Kingdom, 6 June 1 July 2016

Euclid is a European Space Agency medium class mission selected for launch in 2020 within the Cosmic Vision 2015 2025 program. The main goal of Euclid is to understand the origin of the accelerated expansion of the universe. Euclid will explore the expansion history of the universe and the evolution of cosmic structures by measuring shapes and redshifts of galaxies as well as the distribution of clusters of galaxies over a large fraction of the sky. Although the main driver for Euclid is the nature of dark energy, Euclid science covers a vast range of topics, from cosmology to galaxy evolution to planetary research. In this review we focus on cosmology and fundamental physics, with a strong emphasis on science beyond the current standard models. We discuss five broad topics: dark energy and modified gravity, dark matter, initial conditions, basic assumptions and questions of methodology in the data analysis. This review has been planned and carried out within Euclid's Theory Working Group and is meant to provide a guide to the scientific themes that will underlie the activity of the group during the preparation of the Euclid mission., Comment: This article provides an update of arXiv:1206.1225, with different authors. Forecasts are not updated in this version

We measure the location and evolutionary vectors of 69 Herschel-detected broad-line active galactic nuclei (BLAGNs) in the M_BH-M_* plane. BLAGNs are selected from the COSMOS and CDF-S fields, and span the redshift range 0.2< z<2.1. Black-hole masses are calculated using archival spectroscopy and single-epoch virial mass estimators, and galaxy total stellar masses are calculated by fitting the spectral energy distribution (subtracting the BLAGN component). The mass-growth rates of both the black hole and galaxy are calculated using Chandra/XMM-Newton X-ray and Herschel far-infrared data, reliable measures of the BLAGN accretion and galaxy star formation rates, respectively. We use Monte Carlo simulations to account for biases in our sample, due to both selection limits and the steep slope of the massive end of the galaxy stellar-mass distribution. We find our sample is consistent with no evolution in the M_BH-M_* relation from z~2 to z~0. BLAGNs and their host galaxies which lie off the black hole mass galaxy total stellar mass relation tend to have evolutionary vectors anti-correlated with their mass ratios: that is, galaxies with over-massive (under-massive) black holes tend to have a low (high) ratio of the specific accretion rate to the specific star formation rate. We also use the measured growth rates to estimate the preferred AGN duty cycle for our galaxies to evolve most consistently onto the local M_BH-M_Bul relation. Under reasonable assumptions of exponentially declining star formation histories, the data suggest a non-evolving (no more than a factor of a few) BLAGN duty cycle among star-forming galaxies of 10% (1sigma range of 1-42% at z<1 and 2-34% at z>1)., Comment: 26 pages, 13 figures, 2 tables, ApJ accepted

Limited studies have been performed on the radio-loud fraction in X-ray selected type 1 AGN samples. The consistency between various radio-loudness definitions also needs to be checked. We measure the radio-loudness of the 407 type 1 AGNs in the XMM-COSMOS quasar sample using nine criteria from the literature (six defined in the rest-frame and three defined in the observed frame): $R_L=\log(L_{5GHz}/L_B)$, $q_{24}=\log(L_{24\mu m}/L_{1.4GHz})$, $R_{uv}=\log(L_{5GHz}/L_{2500\AA})$, $R_{i}=\log(L_{1.4GHz}/L_i)$, $R_X=\log(\nu L_{\nu}(5GHz)/L_X)$, $P_{5GHz}=\log(P_{5GHz}(W/Hz/Sr))$, $R_{L,obs}=\log(f_{1.4GHz}/f_B)$ (observed frame), $R_{i,obs}=\log(f_{1.4GHz}/f_i)$ (observed frame), and $q_{24, obs}=\log(f_{24\mu m}/f_{1.4GHz})$ (observed frame). Using any single criterion defined in the rest-frame, we find a low radio-loud fraction of $\lesssim 5\%$ in the XMM-COSMOS type 1 AGN sample, except for $R_{uv}$. Requiring that any two criteria agree reduces the radio-loud fraction to $\lesssim 2\%$ for about 3/4 of the cases. The low radio-loud fraction cannot be simply explained by the contribution of the host galaxy luminosity and reddening. The $P_{5GHz}=\log(P_{5GHz}(W/Hz/Sr))$ gives the smallest radio-loud fraction. Two of the three radio-loud fractions from the criteria defined in the observed frame without k-correction ($R_{L,obs}$ and $R_{i,obs}$) are much larger than the radio-loud fractions from other criteria., Comment: 12 pages, 7 figures, MNRAS submitted

[Abridged] With VLT/X-shooter, we obtain optical and NIR spectra of six Ly-alpha blobs at z~2.3. Using three measures --- the velocity offset between the Lya line and the non-resonant [OIII] or H-alpha line (Dv_Lya), the offset of stacked interstellar metal absorption lines, and the spectrally-resolved [OIII] line profile --- we study the kinematics of gas along the line of sight to galaxies within each blob center. These three indicators generally agree in velocity and direction, and are consistent with a simple picture in which the gas is stationary or slowly outflowing at a few hundred km/s from the embedded galaxies. The absence of stronger outflows is not a projection effect: the covering fraction for our sample is limited to <1/8 (13%). The outflow velocities exclude models in which star formation or AGN produce "super" or "hyper" winds of up to ~1000km/s. The Dv_Lya offsets here are smaller than typical of LBGs, but similar to those of compact LAEs. The latter suggests that outflow speed cannot be a dominant factor in driving extended Lya emission. For one Lya blob (CDFS-LAB14), whose Lya profile and metal absorption line offsets suggest no significant bulk motion, we use a simple radiative transfer model to make the first column density measurement of gas in an embedded galaxy, finding it consistent with a DLA system. Overall, the absence of clear inflow signatures suggests that the channeling of gravitational cooling radiation into Lya is not significant over the radii probed here. However, one peculiar system (CDFS-LAB10) has a blueshifted Lya component that is not obviously associated with any galaxy, suggesting either displaced gas arising from tidal interactions among blob galaxies or gas flowing into the blob center. The former is expected in these overdense regions, and the latter might signify the predicted but elusive cold gas accretion along filaments., Comment: 22 pages, 11 figures, accepted for publication in ApJ

We present optical integral field spectroscopy (IFS) observations of the Mice, a major merger between two massive (>10^11Msol) gas-rich spirals NGC4676A and B, observed between first passage and final coalescence. The spectra provide stellar and gas kinematics, ionised gas properties and stellar population diagnostics, over the full optical extent of both galaxies. The Mice provide a perfect case study highlighting the importance of IFS data for improving our understanding of local galaxies. The impact of first passage on the kinematics of the stars and gas has been significant, with strong bars likely induced in both galaxies. The barred spiral NGC4676B exhibits a strong twist in both its stellar and ionised gas disk. On the other hand, the impact of the merger on the stellar populations has been minimal thus far: star formation induced by the recent close passage has not contributed significantly to the global star formation rate or stellar mass of the galaxies. Both galaxies show bicones of high ionisation gas extending along their minor axes. In NGC4676A the high gas velocity dispersion and Seyfert-like line ratios at large scaleheight indicate a powerful outflow. Fast shocks extend to ~6.6kpc above the disk plane. The measured ram pressure and mass outflow rate (~8-20Msol/yr) are similar to superwinds from local ULIRGs, although NGC4676A has only a moderate infrared luminosity of 3x10^10Lsol. Energy beyond that provided by the mechanical energy of the starburst appears to be required to drive the outflow. We compare the observations to mock kinematic and stellar population maps from a merger simulation. The models show little enhancement in star formation during and following first passage, in agreement with the observations. We highlight areas where IFS data could help further constrain the models., Comment: 23 pages, 13 figures, accepted to A&A. A version with a complete set of high resolution figures is available here: http://www-star.st-and.ac.uk/~vw8/resources/mice_v8_astroph.pdf

We perform a quantitative morphological comparison between the hosts of Active Galactic Nuclei (AGN) and quiescent galaxies at intermediate redshifts (z~0.7). The imaging data are taken from the large HST/ACS mosaics of the GEMS and STAGES surveys. Our main aim is to test whether nuclear activity at this cosmic epoch is triggered by major mergers. Using images of quiescent galaxies and stars, we create synthetic AGN images to investigate the impact of an optical nucleus on the morphological analysis of AGN hosts. Galaxy morphologies are parameterized using the asymmetry index A, concentration index C, Gini coefficient G and M20 index. A sample of ~200 synthetic AGN is matched to 21 real AGN in terms of redshift, host brightness and host-to-nucleus ratio to ensure a reliable comparison between active and quiescent galaxies. The optical nuclei strongly affect the morphological parameters of the underlying host galaxy. Taking these effects into account, we find that the morphologies of the AGN hosts are clearly distinct from galaxies undergoing violent gravitational interactions. In fact, the host galaxies' distributions in morphological descriptor space are more similar to undisturbed galaxies than major mergers. Intermediate-luminosity (Lx < 10^44 erg/s) AGN hosts at z~0.7 show morphologies similar to the general population of massive galaxies with significant bulges at the same redshifts. If major mergers are the driver of nuclear activity at this epoch, the signatures of gravitational interactions fade rapidly before the optical AGN phase starts, making them undetectable on single-orbit HST images, at least with usual morphological descriptors. This could be investigated in future synthetic observations created from numerical simulations of galaxy-galaxy interactions., Comment: Accepted for publication in Astronomy and Astrophysics; 17 pages, 30 figures; reposted with affiliation updates and language editing

We define a quasar-galaxy mixing diagram using the slopes of their spectral energy distributions (SEDs) from 1\mu m to 3000\AA\ and from 1\mu m to 3\mu m in the rest frame. The mixing diagram can easily distinguish among quasar-dominated, galaxy-dominated and reddening-dominated SED shapes. By studying the position of the 413 XMM selected Type 1 AGN in the wide-field "Cosmic Evolution Survey" (COSMOS) in the mixing diagram, we find that a combination of the Elvis et al. (1994, hereafter E94) quasar SED with various contributions from galaxy emission and some dust reddening is remarkably effective in describing the SED shape from 0.3-3\mu m for large ranges of redshift, luminosity, black hole mass and Eddington ratio of type 1 AGN. In particular, the location in the mixing diagram of the highest luminosity AGN is very close (within 1\sigma) to that of the E94 SED. The mixing diagram can also be used to estimate the host galaxy fraction and reddening in quasar. We also show examples of some outliers which might be AGN in different evolutionary stages compared to the majority of AGN in the quasar-host galaxy co-evolution cycle., Comment: 19 pages, 13 figures, 2 tables, accepted by MNRAS

The mid-infrared to ultraviolet (0.1 -- 10 $\mu m$) spectral energy distribution (SED) shapes of 407 X-ray-selected radio-quiet type 1 AGN in the wide-field ``Cosmic Evolution Survey" (COSMOS) have been studied for signs of evolution. For a sub-sample of 200 radio-quiet quasars with black hole mass estimates and host galaxy corrections, we studied their mean SEDs as a function of a broad range of redshift, bolometric luminosity, black hole mass and Eddington ratio, and compared them with the Elvis et al. (1994, E94) type 1 AGN mean SED. We found that the mean SEDs in each bin are closely similar to each other, showing no statistical significant evidence of dependence on any of the analyzed parameters. We also measured the SED dispersion as a function of these four parameters, and found no significant dependencies. The dispersion of the XMM-COSMOS SEDs is generally larger than E94 SED dispersion in the ultraviolet, which might be due to the broader ``window function'' for COSMOS quasars, and their X-ray based selection., Comment: 17 pages, 11 figures, 7 tables, MNRAS accepted

Euclid is a European Space Agency medium class mission selected for launch in 2019 within the Cosmic Vision 2015-2025 programme. The main goal of Euclid is to understand the origin of the accelerated expansion of the Universe. Euclid will explore the expansion history of the Universe and the evolution of cosmic structures by measuring shapes and redshifts of galaxies as well as the distribution of clusters of galaxies over a large fraction of the sky. Although the main driver for Euclid is the nature of dark energy, Euclid science covers a vast range of topics, from cosmology to galaxy evolution to planetary research. In this review we focus on cosmology and fundamental physics, with a strong emphasis on science beyond the current standard models. We discuss five broad topics: dark energy and modified gravity, dark matter, initial conditions, basic assumptions and questions of methodology in the data analysis. This review has been planned and carried out within Euclid's Theory Working Group and is meant to provide a guide to the scientific themes that will underlie the activity of the group during the preparation of the Euclid mission., Comment: 236 pages, minor edits to match the journal version 2013

We present an automatic method to identify galaxy mergers using the morphological information contained in the residual images of galaxies after the subtraction of a Sersic model. The removal of the bulk signal from the host galaxy light is done with the aim of detecting the fainter minor mergers. The specific morphological parameters that are used in the merger diagnostic suggested here are the Residual Flux Fraction and the asymmetry of the residuals. The new diagnostic has been calibrated and optimized so that the resulting merger sample is very complete. However, the contamination by non-mergers is also high. If the same optimization method is adopted for combinations of other structural parameters such as the CAS system, the merger indicator we introduce yields merger samples of equal or higher statistical quality than the samples obtained through the use of other structural parameters. We explore the ability of the method presented here to select minor mergers by identifying a sample of visually classified mergers that would not have been picked up by the use of the CAS system, when using its usual limits. Given the low prevalence of mergers among the general population of galaxies and the optimization used here, we find that the merger diagnostic introduced in this work is best used as a negative merger test, i.e., it is very effective at selecting non-merging galaxies. As with all the currently available automatic methods, the sample of merger candidates selected is contaminated by non-mergers, and further steps are needed to produce a clean sample. This merger diagnostic has been developed using the HST/ACS F606W images of the A901/02 cluster (z=0.165) obtained by the STAGES team. In particular, we have focused on a mass and magnitude limited sample (log M/M_{O}>9.0, R_{Vega}<23.5mag)) which includes 905 cluster galaxies and 655 field galaxies of all morphological types., Comment: 25 pages, 14 figures, 4 tables. To appear in MNRAS

We present new constraints on the ratio of black hole (BH) mass to total galaxy stellar mass at 0.3

We present an analysis of V-band radial surface brightness profiles for spiral galaxies from the field and cluster environments using Hubble Space Telescope/Advanced Camera for Surveys imaging and data from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). We use a large sample of ~330 face-on to intermediately inclined spiral galaxies and assess the effect of the galaxy environment on the azimuthally averaged radial surface brightness mu profiles for each galaxy in the outer stellar disc (24 < mu < 26.5 mag per sq arcsec). For galaxies with a purely exponential outer disc (~50 per cent), we determine the significance of an environmental dependence on the outer disc scalelength h_out. For galaxies with a broken exponential in their outer disc, either down-bending (truncation, ~10 per cent) or up-bending (anti-truncation, ~40 per cent), we measure the strength T (outer-to-inner scalelength ratio, log_10(h_out/h_in) of the mu breaks and determine the significance of an environmental dependence on break strength T. Surprisingly, we find no evidence to suggest any such environmental dependence on either outer disc scalelength h_out or break strength T, implying that the galaxy environment is not affecting the stellar distribution in the outer stellar disc. We also find that for galaxies with small effective radii (r_e < 3 kpc) there is a lack of outer disc truncations in both the field and cluster environments. Our results suggest that the stellar distribution in the outer disc of spiral galaxies is not significantly affected by the galaxy environment., Comment: Accepted to MNRAS. Appendix A available at http://www.nottingham.ac.uk/~ppxdtm/STAGES_profiles_appendix.pdf

Testing theories of angular-momentum acquisition of rotationally supported disc galaxies is the key to understand the formation of this type of galaxies. The tidal-torque theory tries to explain this acquisition process in a cosmological framework and predicts positive autocorrelations of angular-momentum orientation and spiral-arm handedness on distances of 1Mpc/h. This disc alignment can also cause systematic effects in weak-lensing measurements. Previous observations claimed discovering such correlations but did not account for errors in redshift, ellipticity and morphological classifications. We explain how to rigorously propagate all important errors. Analysing disc galaxies in the SDSS database, we find that positive autocorrelations of spiral-arm handedness and angular-momentum orientations on distances of 1Mpc/h are plausible but not statistically significant. This result agrees with a simple hypothesis test in the Local Group, where we find no evidence for disc alignment. Moreover, we demonstrate that ellipticity estimates based on second moments are strongly biased by galactic bulges, thereby corrupting correlation estimates and overestimating the impact of disc alignment on weak-lensing studies. Finally, we discuss the potential of future sky surveys. We argue that photometric redshifts have too large errors, i.e., PanSTARRS and LSST cannot be used. We also discuss potentials and problems of front-edge classifications of galaxy discs in order to improve estimates of angular-momentum orientation., Comment: 20 pages, 15 figures; accepted by MNRAS

Parametrising galaxy morphologies is a challenging task, e.g., in shear measurements of weak lensing or investigations of galaxy evolution. The huge variety of morphologies requires an approach that is highly flexible, e.g., accounting for azimuthal structure. We revisit the method of sersiclets, where galaxy morphologies are decomposed into basis functions based on the Sersic profile. This approach is justified by the fact that the Sersic profile is the first-order Taylor expansion of any real light profile. We show that sersiclets overcome the modelling failures of shapelets. However, sersiclets implicate an unphysical relation between the steepness of the light profile and the spatial scale of azimuthal structures, which is not obeyed by real galaxy morphologies and can therefore give rise to modelling failures. Moreover, we demonstrate that sersiclets are prone to undersampling, which restricts sersiclet modelling to highly resolved galaxy images. Analysing data from the Great08 challenge, we demonstrate that sersiclets should not be used in weak-lensing studies. We conclude that although the sersiclet approach appears very promising at first glance, it suffers from conceptual and practical problems that severly limit its usefulness. The Sersic profile can be enhanced by higher-order terms in the Taylor expansion, which can drastically improve model reconstructions of galaxy images. If orthonormalised, these higher-order profiles can overcome the problems of sersiclets while preserving their mathematical justification., Comment: 14 pages, 12 figures, 2 tables; accepted by MNRAS

Exploring the origin of Ly-alpha nebulae (blobs) requires measurements of their gas kinematics that are impossible with only the resonant, optically-thick LyA line. To define gas motions relative to the systemic velocity of the blob, the LyA line must be compared with an optically-thin line like Halpha, which is not much altered by radiative transfer effects. We obtain optical and NIR spectra of the two brightest LyA blobs from Yang et al. sample using the Magellan/MagE and VLT/SINFONI. Both the LyA and Halpha lines confirm that these blobs lie at the survey redshift, z~2.3. Within each blob, we detect several Halpha sources, which roughly correspond to galaxies seen in HST images. The Halpha detections show that these galaxies have large internal velocity dispersions (130 - 190km/s) and that, in the one system (LAB01), their velocity difference is ~440 km/s. The presence of multiple galaxies within the blobs, and those galaxies' large velocity dispersions and large relative motion, is consistent with our previous finding that LyA blobs inhabit massive dark matter halos that will evolve into those typical of rich clusters today. To determine whether the gas near the embedded galaxies is predominantly infalling or outflowing, we compare the LyA and Halpha line centers, finding that LyA is not offset (Delta LyA = +0km/s) in LAB01 and redshifted by only +230 km/s in LAB02. These offsets are small compared to those of Lyman break galaxies, which average +450 km/s and extend to about +700 km/s. We test and rule out the simplest infall models and those outflow models with super/hyper-winds, which require large outflow velocities. Because of the unknown geometry of the gas distribution and the possibility of multiple sources of LyA emission embedded in the blobs, a larger sample and more sophisticated models are required to test more complex or a wider range of infall and outflow scenarios., Comment: Accepted for publication in ApJ, 14 pages, 6 figures