Search

We perform a homogeneous analysis of an unprecedented set of spatially resolved scaling relations (SRs) between ISM components and other properties in the range of scales 0.3-3.4 kpc. We also study some ratios: dust-to-stellar, dust-to-gas, and dust-to-metal. We use a sample of 18 large, spiral, face-on DustPedia galaxies. All the SRs are moderate/strong correlations except the dust-HI SR that does not exist or is weak for most galaxies. The SRs do not have a universal form but each galaxy is characterized by distinct correlations, affected by local processes and galaxy peculiarities. The SRs hold starting from 0.3 kpc, and if a breaking down scale exists it is < 0.3 kpc. By evaluating all galaxies at 3.4 kpc, differences due to peculiarities of individual galaxies are cancelled out and the corresponding SRs are consistent with those of whole galaxies. By comparing subgalactic and global scales, the most striking result emerges from the SRs involving ISM components: the dust-total gas SR is a good correlation at all scales, while the dust-H2 and dust-HI SRs are good correlations at subkpc/kpc and total scales, respectively. For the other explored SRs, there is a good agreement between small and global scales and this may support the picture where the main physical processes regulating the properties and evolution of galaxies occur locally. Our results are consistent with the hypothesis of self-regulation of the SF process. The analysis of subgalactic ratios shows that they are consistent with those derived for whole galaxies, from low to high z, supporting the idea that also these ratios could be set by local processes. Our results highlight the heterogeneity of galaxy properties and the importance of resolved studies on local galaxies in the context of galaxy evolution. They also provide observational constraints to theoretical models and updated references for high-z studies., 42 pages, 11 figures and 5 tables in the main text, 2 figures and 1 table in Appendix. Accepted for publication in A&A

We present a new measurement of the gas-phase mass-metallicity relation (MZR), and its dependence on star formation rates (SFRs) at 1.3 < z < 2.3. Our sample comprises 1056 galaxies with a mean redshift of z = 1.9, identified from the Hubble Space Telescope Wide Field Camera 3 (WFC3) grism spectroscopy in the Cosmic Assembly Near-Infrared Deep Extragalactic Survey (CANDELS) and the WFC3 Infrared Spectroscopic Parallel Survey (WISP). This sample is four times larger than previous metallicity surveys at z ~ 2, and reaches an order of magnitude lower in stellar mass (10^8 M_sun). Using stacked spectra, we find that the MZR evolves by 0.3 dex relative to z ~ 0.1. Additionally, we identify a subset of 49 galaxies with high signal-to-noise (SNR) spectra and redshifts between 1.3 < z < 1.5, where H-alpha emission is observed along with [OIII] and [OII]. With accurate measurements of SFR in these objects, we confirm the existence of a mass-metallicity-SFR (M-Z-SFR) relation at high redshifts. These galaxies show systematic differences from the local M-Z-SFR relation, which vary depending on the adopted measurement of the local relation. However, it remains difficult to ascertain whether these differences could be due to redshift evolution, as the local M-Z-SFR relation is poorly constrained at the masses and SFRs of our sample. Lastly, we reproduced our sample selection in the IllustrisTNG hydrodynamical simulation, demonstrating that our line flux limit lowers the normalization of the simulated MZR by 0.2 dex. We show that the M-Z-SFR relation in IllustrisTNG has an SFR dependence that is too steep by a factor of around three., Accepted for publication in ApJ; 41 pages, 20 figures

We identify a sample of spectroscopically measured emission line galaxy (ELG) pairs up to z=1.6 from the WFC3 Infrared Spectroscopic Parallels (WISP) survey. WISP obtained slitless, near-infrared grism spectroscopy along with direct imaging in the J and H bands by observing in the pure-parallel mode with the Wide Field Camera Three (WFC3) on the Hubble Space Telescope (HST). From our search of 419 WISP fields covering an area of ~0.5 deg$^{2}$, we find 413 ELG pair systems, mostly Halpha emitters. We then derive reliable star formation rates (SFRs) based on the attenuation-corrected Halpha fluxes. Compared to isolated galaxies, we find an average SFR enhancement of 40%-65%, which is stronger for major pairs and pairs with smaller velocity separations (Delta_v < 300 km/s). Based on the stacked spectra from various subsamples, we study the trends of emission line ratios in pairs, and find a general consistency with enhanced lower-ionization lines. We study the pair fraction among ELGs, and find a marginally significant increase with redshift $f \propto (1+z)^\alpha$, where the power-law index \alpha=0.58$\pm$0.17 from $z\sim$0.2 to $z\sim$1.6. The fraction of Active galactic Nuclei (AGNs), is found to be the same in the ELG pairs as compared to isolated ELGs., Comment: 22 pages, 9 figures, 6 tables, accepted for publication in ApJ

The Multi Conjugate Adaptive Optics RelaY (MAORY) for the ESO Extremely Large Telescope (ELT) is an Adaptive Optics module offering Multi-Conjugate (MCAO) and Single-Conjugate (SCAO) compensation modes. In MCAO, it relies on the use of a constellation of Laser Guide Stars (LGS) and up to three Natural Guide Stars (NGS) for atmospheric turbulence sensing, and multiple deformable mirrors for correction, providing uniform, high Strehl and high sky coverage. MAORY will be installed at the Nasmyth focus of the E-ELT and will feed the MICADO first-light diffraction limited imager and a future second instrument. MAORY is being built by a Consortium composed by INAF in Italy, IPAG in France and the School of Physics at the National University of Ireland Galway. In this paper we report about the status of the design of the MAORY Real Time Computer, which is the component in charge of implementing the main AO control loops, as well as of auxiliary computations to keep the loops operating optimally, and of telemetry data collection for postprocessing, monitoring, testing and troubleshooting. We will start by discussing the evolution of requirements towards MAORY RTC, with an emphasis on the main driving ones. Then, we will describe how the analysis of requirements has led to the derivation of the main design parameters. Finally, we will illustrate possible RTC designs satisfying user requirements, while also complying with standards set forth by ESO.

Context. Dusty high-z galaxies are extreme objects with high star formation rates (SFRs) and luminosities. Characterising the properties of this population and analysing their evolution over cosmic time is key to understanding galaxy evolution in the early Universe. Aims. We select a sample of high-z dusty star-forming galaxies (DSFGs) and evaluate their position on the main sequence (MS) of star-forming galaxies, the well-known correlation between stellar mass and SFR. We aim to understand the causes of their high star formation and quantify the percentage of DSFGs that lie above the MS. Methods. We adopted a multi-wavelength approach with data from optical to submillimetre wavelengths from surveys at the North Ecliptic Pole to study a submillimetre sample of high-redshift galaxies. Two submillimetre selection methods were used, including: sources selected at 850 μm with the Sub-millimetre Common-User Bolometer Array 2) SCUBA-2 instrument and Herschel-Spectral and Photometric Imaging Receiver (SPIRE) selected sources (colour-colour diagrams and 500 μm risers), finding that 185 have good multi-wavelength coverage. The resulting sample of 185 high-z candidates was further studied by spectral energy distribution fitting with the CIGALE fitting code. We derived photometric redshifts, stellar masses, SFRs, and additional physical parameters, such as the infrared luminosity and active galactic nuclei (AGN) contribution. Results. We find that the Herschel-SPIRE selected DSFGs generally have higher redshifts (z = 2.57−0.09+0.08) than sources that are selected solely by the SCUBA-2 method (z = 1.45−0.06+0.21). We find moderate SFRs (797−50+108 M⊙ yr−1), which are typically lower than those found in other studies. We find that the different results in the literature are, only in part, due to selection effects, as even in the most extreme cases, SFRs are still lower than a few thousand solar masses per year. The difference in measured SFRs affects the position of DSFGs on the MS of galaxies; most of the DSFGs lie on the MS (60%). Finally, we find that the star formation efficiency (SFE) depends on the epoch and intensity of the star formation burst in the galaxy; the later the burst, the more intense the star formation. We discuss whether the higher SFEs in DSFGs could be due to mergers.

Future surveys focusing on understanding the nature of dark energy (e.g., Euclid and WFIRST) will cover large fractions of the extragalactic sky in near-IR slitless spectroscopy. These surveys will detect a large number of galaxies that will have only one emission line in the covered spectral range. In order to maximize the scientific return of these missions, it is imperative that single emission lines are correctly identified. Using a supervised machine-learning approach, we classified a sample of single emission lines extracted from the WFC3 IR Spectroscopic Parallel survey, one of the closest existing analogs to future slitless surveys. Our automatic software integrates a spectral energy distribution (SED)-fitting strategy with additional independent sources of information. We calibrated it and tested it on a "gold" sample of securely identified objects with multiple lines detected. The algorithm correctly classifies real emission lines with an accuracy of 82.6%, whereas the accuracy of the SED-fitting technique alone is low (∼50%) due to the limited amount of photometric data available (≤6 bands). While not specifically designed for the Euclid and WFIRST surveys, the algorithm represents an important precursor of similar algorithms to be used in these future missions.

The mutually complementary Euclid and Roman galaxy redshift surveys will use Halpha- and [OIII]-selected emission line galaxies as tracers of the large scale structure at $0.9 \lesssim z \lesssim 1.9$ (Halpha) and $1.5 \lesssim z \lesssim 2.7$ ([OIII]). It is essential to have a reliable and sufficiently precise knowledge of the expected numbers of Halpha-emitting galaxies in the survey volume in order to optimize these redshift surveys for the study of dark energy. Additionally, these future samples of emission-line galaxies will, like all slitless spectroscopy surveys, be affected by a complex selection function that depends on galaxy size and luminosity, line equivalent width, and redshift errors arising from the misidentification of single emission-line galaxies. Focusing on the specifics of the Euclid survey, we combine two slitless spectroscopic WFC3-IR datasets -- 3D-HST+AGHAST and the WISP survey -- to construct a Euclid-like sample that covers an area of 0.56 deg$^2$ and includes 1277 emission line galaxies. We detect 1091 ($\sim$3270 deg$^{-2}$) Halpha+[NII]-emitting galaxies in the range $0.9\leq z \leq 1.6$ and 162 ($\sim$440 deg$^{-2}$) [OIII]$\lambda$5007-emitters over $1.5\leq z \leq 2.3$ with line fluxes $\geq 2 \times 10^{-16}$ erg s$^{-1}$ cm$^{-2}$. The median of the Halpha+[NII] equivalent width distribution is $\sim$250\r{A}, and the effective radii of the continuum and Halpha+[NII] emission are correlated with a median of $\sim$0.38" and significant scatter ($\sigma \sim $0.2"$-$0.35"). Finally, we explore the prevalence of redshift misidentification in future Euclid samples, finding potential contamination rates of $\sim$14-20% and $\sim$6% down to $2\times 10^{-16}$ and $6 \times 10^{-17}$ erg s$^{-1}$ cm$^{-2}$, respectively, though with increased wavelength coverage these percentages drop to nearly zero., Comment: Accepted for publication in ApJ. 27 pages, 17 figures, 3 tables

We quantify the star formation (SF) in the inner cores (R/R_(200) ≤0.3) of 24 massive galaxy clusters at 0.2 10^(10) Mꙩ) samples of star-forming cluster members (not)-detected in the mid- and/or far-infrared. We release the catalogues with the photometry, photometric redshifts, and physical properties of these samples. We also quantify the SF displayed by comparable field samples from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. We find that in intermediatez cluster cores, the SF activity is suppressed with respect the field in terms of both the fraction (F) of star-forming galaxies (SFGs) and the rate at which they form stars (SFR and sSFR = SFR/M∗). On average, the F of SFGs is a factor ∼2 smaller in cluster cores than in the field. Furthermore, SFGs present average SFR and sSFR typically ∼0.3 dex smaller in the clusters than in the field along the whole redshift range probed. Our results favour long time-scale quenching physical processes as the main driver of SF suppression in the inner cores of clusters since z ∼0.9, with shorter time-scale processes being very likely responsible for a fraction of the missing SFG population.

We study the co-evolution between the black hole accretion rate (BHAR) and the star formation rate (SFR) in different galaxy life phases: main sequence star-forming galaxies, quiescent and starburst galaxies at different cosmic epochs. We take advantage of the X-ray data from the Chandra COSMOS-Legacy survey and of the extensive multiwavelength ancillary observations in the COSMOS field presented in the COSMOS2015 catalog. We perform an X-ray stacking analysis and combine it with detected sources, in a broad redshift interval ($0.1, Comment: 18 pages, 6 figures; Accepted for publication in A&A

We investigate the nature of star-forming galaxies with reduced specific star formation rate (sSFR) and high stellar masses, those `green valley' objects that seemingly cause a reported bending, or flattening, of the star-forming main sequence. The fact that such objects host large bulges recently led some to suggest that the internal formation of bulges was a late event that induced the sSFRs of massive galaxies to drop in a slow downfall, and thus the main sequence to bend. We have studied in detail a sample of 10 galaxies at $0.45, Comment: 26 pages, 19 figures, accepted by MNRAS

Based on the novel data pertaining to five syntactic phenomena (the position of the finite verb in embedded clauses, in sentences with a modal verb, negative concord, the position of focused light/heavy objects in main clauses with a complex tense and scrambling) in the heritage language Mòcheno collected via original fieldwork, we show that there are two populations – one exhibiting intra-speaker variation between German and Italian word orders, and one lacking it; and these two populations are the result of diatopic variation and, to a lesser extent, of diastratic variation. The results achieved using quantitative statistical analysis are partially convergent with those arrived at via the traditional theoretical syntax for Mòcheno, but our analysis has allowed us to shed new light on a series of phenomena that have been neglected or poorly understood thus far. More specifically, and for the first time, we discovered that there is a micro-variation resulting from diastratic (age) variation within the Roveda variety, which represents the only case in Mòcheno in which age is a relevant factor in determining variation. We also show that the traditional claim that the Palù variety is ‘more German’ than is the other Mòcheno variety is to be confirmed; however, we could refine it by showing that German word orders are also accepted by speakers of other varieties and that the acceptability of these word orders in competition with the Italian syntax is not due to their age (no diastratic variation). Finally, we show that the acceptance of German word orders across speakers varies according to the phenomenon investigated: German word orders are more likely to be accepted in sentences featuring a negation, whereas German word orders are more likely to be rejected in embedded clauses. Based on this fine-grained description of the distribution of OV/VO word orders across different contexts and groups and the available theoretical account for the derivation of OV word order given by Cognola (2013b), we propose that the observed variation can be parametrized along the lines of recent developments of Parameter Theory (Roberts, 2012; Biberauer et al., 2014 a.o.). More specifically, we propose that the movement of the non-finite verb form to lowForce°, which is responsible for OV in Mòcheno, can be captured in terms of a parametric hierarchy. When verb movement takes place in all syntactic conditions, including with all non-finite verb forms and when the auxiliary has not moved out of v° to Spec, CP, a macroparametric effect obtains which corresponds to the system instantiated by the Palù variety. The mesoparameter corresponds to a system in which the movement to the non-finite verb form can only be found when v° is empty, i.e., in main declarative clauses. The fact that for a subgroup of speakers from Fierozzo and Roveda OV word order is accepted with modal verbs follows from a microparamter: the movement of the non-finite verb form to lowFocus° can only take place with non-finite verbs. Finally, the fact that OV is obligatory for nearly all groups is captured in terms of a nanoparamenter associated with negative constituents.

We illustrate the extraordinary potential of the (far-IR) Origins Survey Spectrometer (OSS) on board the Origins Space Telescope (OST) to address a variety of open issues on the co-evolution of galaxies and AGNs. We present predictions for blind surveys, each of 1000 h, with different mapped areas (a shallow survey covering an area of 10 deg$^{2}$ and a deep survey of 1 deg$^{2}$) and two different concepts of the OST/OSS: with a 5.9 m telescope (Concept 2, our reference configuration) and with a 9.1 m telescope (Concept 1, previous configuration). In 1000 h, surveys with the reference concept will detect from $\sim 1.9 \times 10^{6}$ to $\sim 8.7 \times 10^{6}$ lines from $\sim 4.8 \times 10^{5}$-$2.7 \times 10^{6}$ star-forming galaxies and from $\sim 1.4 \times 10^{4}$ to $\sim 3.8 \times 10^{4}$ lines from $\sim 1.3 \times 10^{4}$-$3.5 \times 10^{4}$ AGNs. The shallow survey will detect substantially more sources than the deep one; the advantage of the latter in pushing detections to lower luminosities/higher redshifts turns out to be quite limited. The OST/OSS will reach, in the same observing time, line fluxes more than one order of magnitude fainter than the SPICA/SMI and will cover a much broader redshift range. In particular it will detect tens of thousands of galaxies at $z \geq 5$, beyond the reach of that instrument. The polycyclic aromatic hydrocarbons lines are potentially bright enough to allow the detection of hundreds of thousands of star-forming galaxies up to $z \sim 8.5$, i.e. all the way through the re-ionization epoch. The proposed surveys will allow us to explore the galaxy-AGN co-evolution up to $z\sim 5.5-6$ with very good statistics. OST Concept 1 does not offer significant advantages for the scientific goals presented here., Comment: 24 pages, 20 figures, 2 tables, accepted for publication in PASA

We investigate a sample of 152 dusty sources at 1.5 z Herschel-selected, having stellar masses M * > 1010 M ⊙ and SFR (~100–1000 M ⊙ yr−1) elevated (>4×) above the star-forming "main sequence," classifying them as starbursts (SBs). Through a multiwavelength fitting approach (including a dusty torus component), we divided the sample into active SBs (dominated by an active galactic nucleus (AGN) emission, SBs-AGN, ~23% of the sample) and purely star-forming SBs (SBs-SFR). We visually inspected their Hubble Space Telescope/ultraviolet (UV) rest frame maps: SBs-SFR are generally irregular and composite systems; ~50% of SBs-AGN are instead dominated by regular compact morphologies. We then found archival Atacama Large Millimeter/submillimeter Array continuum counterparts for 33 galaxies (12 SBs-AGN and 21 SBs-SFR). For these sources we computed dust masses, and, with standard assumptions, we also guessed total molecular gas masses. SBs turn into gas-rich systems (f gas = M gas/(M gas + M *) 20%–70%), and the gas fractions of the two SB classes are very similar (f gas = 43% ± 4% and f gas = 42% ± 2%). Our results show that SBs are consistent with a mixture of: (1) highly star-forming merging systems (dominating the SBs-SFR) and (2) primordial galaxies, rapidly growing their M * together with their black hole (mainly the more compact SBs-AGN). Feedback effects have not yet reduced their f gas. Indeed, SBs at z = 2, with relatively low bolometric AGN luminosities in the range 1044 L bol(AGN) 46 erg s−1 (compared to bright optical and X-ray quasars), are still relatively far from the epoch when the AGN feedback will quench the SFR in the host and will substantially depress the gas fractions.

We present the results of Galaxy Nurseries project, which was designed to enable crowdsourced analysis of slitless spectroscopic data by volunteer citizen scientists using the Zooniverse online interface. The dataset was obtained by the WFC3 Infrared Spectroscopic Parallel (WISP) Survey collaboration and comprises NIR grism (G102 and G141) and direct imaging. Volunteers were instructed to evaluate indicated spectral features and decide whether it was a genuine emission line or more likely an artifact. Galaxy Nurseries was completed in only 40 days, gathering 414,360 classifications from 3003 volunteers for 27,333 putative emission lines. The results of Galaxy Nurseries demonstrate the feasibility of identifying genuine emission lines in slitless spectra by citizen scientists. Volunteer responses for each subject were aggregated to compute $f_{\mathrm{Real}}$, the fraction of volunteers who classified the corresponding emission line as "Real". To evaluate the accuracy of volunteer classifications, their aggregated responses were compared with independent assessments provided by members of the WISP Survey Science Team (WSST). Overall, there is a broad agreement between the WSST and volunteers' classifications, although we recognize that robust scientific analyses typically require samples with higher purity and completeness than raw volunteer classifications provide. Nonetheless, choosing optimal threshold values for $f_{\mathrm{Real}}$ allows a large fraction of spurious lines to be vetoed, substantially reducing the timescale for subsequent professional analysis of the remaining potential lines., Comment: Accepted for publication in Research Notes of the AAS

For a sample of star forming galaxies in the redshift interval 0.15$, Comment: 31 pages, 23 figures

The James Webb Space Telescope's Medium Resolution Spectrometer (MRS), will offer nearly 2 orders of magnitude improvement in sensitivity and >3X improvement in spectral resolution over our previous space-based mid-IR spectrometer, the Spitzer IRS. In this paper, we make predictions for spectroscopic pointed observations and serendipitous detections with the MRS. Specifically, pointed observations of Herschel sources require only a few minutes on source integration for detections of several star-forming and active galactic nucleus lines, out to z$=$3 and beyond. But the same data will also include tens of serendipitous 0$\lesssim$z$\lesssim$4 galaxies per field with infrared luminosities ranging $\sim10^6-10^{13}$L$_{\odot}$. In particular, for the first time and for free we will be able to explore the $L_{IR}, 31 pages, 12 figures, accepted for publication in ApJ

How does the presence of an AGN influence the total SFR estimates of galaxies and change their distribution with respect to the Galaxy Main Sequence? To contribute to solving this question, we study a sample of 1133 sources detected in the North Ecliptic Pole field (NEP) by AKARI and Herschel. We create a multi-wavelength dataset for these galaxies and we fit their multi-wavelength Spectral Energy Distribution (SED) using the whole spectral regime (from 0.1 to 500 µm). We perform the fit using three procedures: LePhare and two optimised codes for identifying AGN tracers from the SED analysis. In this work we present an overview of the comparison between the estimates of the Infrared bolometric luminosities (between 8 and 1000 µm) and the AGN fractions obtained exploiting these different procedures. In particular, by estimating the AGN contribution in four different wavelength ranges (5-40 µm, 10-20 µm, 20-40 µm and 8-1000 µm) we show how the presence of an AGN affects the PAH emission by suppressing the ratio L8 µm/ L4.5 µm as a function of the considered wavelength range.

We present a summary of our spectroscopic redshift catalogue of 404 sources in the AKARI Deep Field South (ADF-S). We have used the AAOmega spectrograph to target mid-infrared and far-infrared sources selected primarily from AKARI observations in this field for which we were able to obtain optical counterparts. Our sources with identified redshifts include 316 with Hα detections at z ≤ 0.345 and 15 sources at z > 1 with MgII or Lα emission lines. About 13% of our z ≤ 0.345 sources are dominated by active galactic nuclei (AGN) emission, although many show emission from both star formation and AGNs. The median Balmer decrement is 5.9. Ultra-luminous infrared galaxies (ULIRGs) were found only in the higher-redshift sources. Optical and near infrared data will be available shortly, enabling calibration of the line luminosities and spectral energy distribution (SED) fitting for these sources.

International audience; We present the results of a systematic search for Lyα emitters (LAEs) at $6\lesssim z\lesssim 7.6$ using the HST WFC3 Infrared Spectroscopic Parallel (WISP) Survey. Our total volume over this redshift range is $\sim 8\times {10}^{5}$ Mpc(3), comparable to many of the narrowband surveys despite their larger area coverage. We find two LAEs at z = 6.38 and 6.44 with line luminosities of ${L}_{\mathrm{Ly}\alpha }\sim 4.7\times {10}^{43}$ erg s(−)(1), putting them among the brightest LAEs discovered at these redshifts. Taking advantage of the broad spectral coverage of WISP, we are able to rule out almost all lower-redshift contaminants. The WISP LAEs have a high number density of $7.7\times {10}^{-6}$ Mpc(−)(3). We argue that the LAEs reside in megaparsec-scale ionized bubbles that allow the Lyα photons to redshift out of resonance before encountering the neutral intergalactic medium. We discuss possible ionizing sources and conclude that the observed LAEs alone are not sufficient to ionize the bubbles.

We combined the spectroscopic information from the 3D-HST survey with Herschel data to characterize the Hα dust attenuation properties of a sample of 79 main sequence star-forming galaxies at z ~ 1 in the GOODS-S field. The sample was selected in the far-IR at λ = 100 and/or 160 μm and only includes galaxies with a secure Hα detection (S/N > 3). From the low resolution 3D-HST spectra we measured the redshifts and the Hα fluxes for the whole sample. (A factor of 1/1.2 was applied to the observed fluxes to remove the [NII] contamination.) The stellar masses (M⋆), infrared (LIR), and UV luminosities (LUV) were derived from the spectral energy distributions by fitting multiband data from GALEX near-UV to SPIRE 500 μm. We estimated the continuum extinction Estar(B-V) from both the IRX = LIR/LUV ratio and the UV-slope, β, and found excellent agreement between the two. The nebular extinction was estimated from comparison of the observed SFRHα and SFRUV. We obtained f = Estar(B-V) /Eneb(B-V) = 0.93 ± 0.06, which is higher than the canonical value of f = 0.44 measured in the local Universe. Our derived dust correction produces good agreement between the Hα and IR+UV SFRs for galaxies with SFR ≳ 20M☉/yr and M⋆ ≳ 5 × 1010M☉, while objects with lower SFR and M⋆ seem to require a smaller f-factor (I.e. higher Hα extinction correction). Our results then imply that the nebular extinction for our sample is comparable to extinction in the optical-UV continuum and suggest that the f-factor is a function of both M⋆ and SFR, in agreement with previous studies.

We investigate the co-evolution of black-hole-accretion-rate (BHAR) and star-formation-rate (SFR) in $1.5, Comment: Accepted for publication as ApJ Letter

We compare various star formation rate (SFR) indicators for star-forming galaxies at $1.4, Comment: Accepted for publication in MNRAS

Two main modes of star formation are know to control the growth of galaxies: a relatively steady one in disk-like galaxies, defining a tight star formation rate (SFR)-stellar mass sequence, and a starburst mode in outliers to such a sequence which is generally interpreted as driven by merging. Such starburst galaxies are rare but have much higher SFRs, and it is of interest to establish the relative importance of these two modes. PACS/Herschel observations over the whole COSMOS and GOODS-South fields, in conjunction with previous optical/near-IR data, have allowed us to accurately quantify for the first time the relative contribution of the two modes to the global SFR density in the redshift interval 1.51000M(sun)/yr, off-sequence sources significantly contribute to the SFR density (46+/-20%). We conclude that merger-driven starbursts play a relatively minor role for the formation of stars in galaxies, whereas they may represent a critical phase towards the quenching of star formation and morphological transformation in galaxies., Comment: Accepted for publication in ApJ Letters

Star formation in massive galaxies is quenched at some point during hierarchical mass assembly. To understand where and when the quenching processes takes place, we study the evolution of the total star formation rate per unit total halo mass (\Sigma(SFR/M)) in three different mass scales: low mass halos (field galaxies), groups, and clusters, up to a redshift ~1.6. We use deep far-infrared PACS data at 100 and 160 um to accurately estimate the total star formation rate of the Luminous Infrared Galaxy population of 9 clusters with mass ~10^{15} M_{\odot}, and 9 groups/poor clusters with mass ~ 5 x 10^{13} M_{\odot}. Estimates of the field \Sigma(SFR/M) are derived from the literature, by dividing the star formation rate density by the mean comoving matter density of the universe. The field \Sigma(SFR/M) increases with redshift up to z~1 and it is constant thereafter. The evolution of the \Sigma(SFR/M)-z relation in galaxy systems is much faster than in the field. Up to redshift z~0.2, the field has a higher \Sigma(SFR/M) than galaxy groups and galaxy clusters. At higher redshifts, galaxy groups and the field have similar \Sigma(SFR/M), while massive clusters have significantly lower \Sigma(SFR/M) than both groups and the field. There is a hint of a reversal of the SFR activity vs. environment at z~1.6, where the group \Sigma(SFR/M) lies above the field \Sigma(SFR/M)-z relation. We discuss possible interpretations of our results in terms of the processes of downsizing, and star-formation quenching., Comment: 8 pages, 3 figures, accepted for publication on A&A