Search

We report the multi-wavelength properties of millimeter galaxies hosting X-ray detected active galactic nuclei (AGNs) from the ALMA Lensing Cluster Survey (ALCS). ALCS is an extensive survey of well-studied lensing clusters with ALMA, covering an area of 133 arcmin$^2$ over 33 clusters with a 1.2 mm flux-density limit of ${\sim}$60 $\mathrm{\mu Jy}$ ($1\sigma$). Utilizing the archival data of Chandra, we identify three AGNs at $z=$1.06, 2.09, and 2.84 among the 180 millimeter sources securely detected in the ALCS (of which 155 are inside the coverage of Chandra). The X-ray spectral analysis shows that two AGNs are not significantly absorbed ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2} < 23$), while the other shows signs of moderate absorption ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2}\sim 23.5$). We also perform spectral energy distribution (SED) modelling of X-ray to millimeter photometry. We find that our X-ray AGN sample shows both high mass accretion rates (intrinsic 0.5--8 keV X-ray luminosities of ${\sim}10^{\text{44--45}}\,\mathrm{erg\ s^{-1}}$) and star-formation rates (${\gtrsim}100\,M_{\odot}\,\mathrm{yr}^{-1}$). This demonstrates that a wide-area survey with ALMA and Chandra can selectively detect intense growth of both galaxies and supermassive black holes (SMBHs) in the high-redshift universe., Comment: 14 pages, 3 figures, 2 tables

Using the novel $JWST$/NIRCam observations in the Abell 2744 field, we present a first spatially resolved overview of an $HST$-dark galaxy, spectroscopically confirmed at $z=2.58$ with magnification $\mu\approx1.9$. While being largely invisible at $\sim$1 $\mu$m with NIRCam, except for sparse clumpy sub-structures, the object is well-detected and resolved in the long-wavelength bands with a spiral shape clearly visible in F277W. By combining ancillary ALMA and $Herschel$ data, we infer that this object is an edge-on dusty spiral with an intrinsic stellar mass log$(M_*/M_\odot)\sim11.3$ and a dust-obscured SFR$\sim 300~M_\odot$~yr$^{-1}$. A massive quiescent galaxy (log$(M_*/M_\odot)\sim10.8$) with tidal features lies 2\farcs{0} away ($r$$\sim$9 kpc), at a consistent redshift as inferred by $JWST$ photometry, indicating a potential major merger. The dusty spiral lies on the main-sequence of star formation, and shows high dust attenuation in the optical ($34$ would be only detectable in F356W and F444W in UNCOVER-like survey, and become totally $JWST$-dark at $z\sim6$. This suggests that detecting highly attenuated galaxies in the Epoch of Reionization might be a challenging task for $JWST$., Comment: 15 pages, 5 figures, 1 table. Accepted to ApJL

Support by grant 2020750 from the United States- Israel Binational Science Foundation (BSF) and grant 2109066 from the United States National Science Foundation (NSF), and by the Ministry of Science and Technology, Israel. J.C. acknowl- edges funding from the ‘FirstGalaxies’ Advanced Grant from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant agreement No. 789056). E.C.L. acknowledges support of an STFC Webb Fellowship (ST/W001438/1). K.K. acknowledges the support by JSPS KAKENHI Grant Number JP17H06130 and the NAOJ ALMA Scientific Research Grant Number 2017–06B. D.E. acknowledges support from a Beatriz Galindo senior fellowship (BG20/00224) from the Spanish Ministry of Science and Innovation, projects PID2020-114414GB-100 and PID2020-113689GB-I00 financed by MCIN/AEI/10.13039/501100011033, project P20-00334 financed by the Junta de Andaluc´ıa, and project A-FQM-510-UGR20 of the FEDER/Junta de Andaluc´ıa-Consejer´ıa de Transformaci ´on Econ ´omica, Industria, Conocimiento y Universidades. G.E.M. ac- knowledges financial support from the Villum Young Investiga- tor grant 37440 and 13160 and the The Cosmic Dawn Center (DAWN), funded by the Danish National Research Foundation under grant No. 140. F.E.B. acknowledges support from ANID- Chile BASAL CATA FB210003, FONDECYT Regular 1200495 and 1190818, and Millennium Science Initiative Program–ICN12 009. K.K.K. acknowledges support from the Knut and Alice Wallenberg Foundation., We report the discovery of a triply imaged active galactic nucleus (AGN), lensed by the galaxy cluster MACS J0035.4−2015 (z d = 0.352). The object is detected in Hubble Space Telescope imaging taken for the RELICS program. It appears to have a quasi-stellar nucleus consistent with a point-source, with a de-magnified radius of re ≲ 100 pc. The object is spectroscopically confirmed to be an AGN at z spec = 2.063 ± 0.005 showing broad rest-frame UV emission lines, and detected in both X-ray observations with Chandra and in ALCS ALMA band 6 (1.2 mm) imaging. It has a relatively faint rest-frame UV luminosity for a quasar-like object, MUV, 1450 = −19.7 ± 0.2. The object adds to just a few quasars or other X-ray sources known to be multiply lensed by a galaxy cluster. Some diffuse emission from the host galaxy is faintly seen around the nucleus, and there is a faint object nearby sharing the same multiple-imaging symmetry and geometric redshift, possibly an interacting galaxy or a star-forming knot in the host. We present an accompanying lens model, calculate the magnifications and time delays, and infer the physical properties of the source. We find the rest-frame UV continuum and emission lines to be dominated by the AGN, and the optical emission to be dominated by the host galaxy of modest stellar mass M✶ ≃ 109.2 M⊙. We also observe some variation in the AGN emission with time, which may suggest that the AGN used to be more active. This object adds a low-redshift counterpart to several relatively faint AGN recently uncovered at high redshifts with HST and JWST., Horizon 2020 Framework Programme H2020, Consejería de Transformación Económica, Industria, Conocimiento y Universidades 13160, 37440, Science and Technology Facilities Council ST/W001438/1 STFC, European Research Council ERC, Fondo Nacional de Desarrollo Científico y Tecnológico 1190818, 1200495, ICN12_009 FONDECYT, Ministerio de Ciencia e Innovación MCIN/AEI/10.13039/501100011033, P20-00334, PID2020-113689GB-I00, PID2020-114414GB-100 MICINN, Horizon 2020 789056, European Regional Development Fund ERDF, Junta de Andalucía A-FQM-510-UGR20

We study the interstellar medium (ISM) properties as a function of the molecular gas size for 77 infrared-selected galaxies at $z \sim 1.3$. Molecular gas sizes are measured on ALMA images that combine CO(2-1), CO(5-4) and underlying continuum observations, and include CO(4-3), CO(7-6)+[CI]($^3 P_2-^3P_1$), [CI]($^3 P_1-^3P_0$) observations for a subset of the sample. The $\gtrsim 46 \%$ of our galaxies have a compact molecular gas reservoir, and lie below the optical disks mass-size relation. Compact galaxies on and above the main sequence have higher CO excitation and star formation efficiency than galaxies with extended molecular gas reservoirs, as traced by CO(5-4)/CO(2-1) and CO(2-1)/$L_{\rm IR, SF}$ ratios. Average CO+[CI] spectral line energy distributions indicate higher excitation in compacts relative to extended sources. Using CO(2-1) and dust masses as molecular gas mass tracers, and conversion factors tailored to their ISM conditions, we measure lower gas fractions in compact main-sequence galaxies compared to extended sources. We suggest that the sub-millimetre compactness, defined as the ratio between the molecular gas and the stellar size, is an unavoidable information to be used with the main sequence offset to describe the ISM properties of galaxies, at least above $M_{\star} \geqslant 10^{10.6}$ M$_{\odot}$, where our observations fully probe the main sequence scatter. Our results are consistent with mergers driving the gas in the nuclear regions, enhancing the CO excitation and star formation efficiency. Compact main-sequence galaxies are consistent with being an early post-starburst population following a merger-driven starburst episode, stressing the important role of mergers in the evolution of massive galaxies., Accepted on MNRAS on October 11th 2021. Added Figure 10, 11, 12 following referee's comments. Abstract slightly modified to fit to arXiv's requirements

Star formation in half of massive galaxies was quenched by the time the Universe was three billion years old. Very low amounts of molecular gas appear responsible for this, at least in some cases, though morphological gas stabilization, shock heating, or activity associated with accretion onto a central supermassive black hole is invoked in other cases. Recent studies of quenching by gas depletion have been based upon upper limits that are insufficiently sensitive to determine this robustly, or stacked emission with its problems of averaging. Here we report 1.3mm observations of dust emission from six strongly lensed galaxies where star formation has been quenched, with magnifications of up to a factor of 30. Four of the six galaxies are undetected in dust emission, with an estimated upper limit on the dust mass of 0.0001 times the stellar mass, and by proxy (assuming a Milky Way molecular gas-to-dust ratio) 0.01 times the stellar mass in molecular gas. This is two orders of magnitude less molecular gas per unit stellar mass than seen in star forming galaxies at similar redshifts. It remains difficult to extrapolate from these small samples, but these observations establish that gas depletion is responsible for a cessation of star formation in some fraction of high-redshift galaxies., 17 pages, 3 figures. Authors' version. Published online by Nature on September 22, 2021

We present a detailed study of a galaxy merger taking place at $z=1.89$ in the GOODS-S field. Here we analyze Keck/MOSFIRE spectroscopic observations from the MOSFIRE Deep Evolution Field (MOSDEF) survey along with multi-wavelength photometry assembled by the 3D-HST survey. The combined dataset is modeled to infer the past star-formation histories (SFHs) of both merging galaxies. They are found to be massive, with log$_{10}(M_{\ast}/M_{\odot}) > 11$, with a close mass ratio satisfying the typical major-merger definition. Additionally, in the context of delayed-$\tau$ models, GOODS-S 43114 and GOODS-S 43683 have similar SFHs and low star-formation rates (log$_{10}$(SFR(SED)/$M_{\odot}/\rm{yr}^{-1}$) $, Comment: 12 pages, 7 figures, 1 table, Accepted for publication in MNRAS

We report the discovery of an intrinsically faint, quintuply-imaged, dusty galaxy MACS0600-z6 at a redshift $z=$6.07 viewed through the cluster MACSJ0600.1-2008 ($z$=0.46). A $\simeq4\sigma$ dust detection is seen at 1.2mm as part of the ALMA Lensing Cluster Survey (ALCS), an on-going ALMA Large program, and the redshift is secured via [C II] 158 $\mu$m emission described in a companion paper. In addition, spectroscopic follow-up with GMOS/Gemini-North shows a break in the galaxy's spectrum, consistent with the Lyman break at that redshift. We use a detailed mass model of the cluster and infer a magnification $\mu\gtrsim$30 for the most magnified image of this galaxy, which provides an unprecedented opportunity to probe the physical properties of a sub-luminous galaxy at the end of cosmic reionisation. Based on the spectral energy distribution, we infer lensing-corrected stellar and dust masses of $\rm{2.9^{+11.5}_{-2.3}\times10^9}$ and $\rm{4.8^{+4.5}_{-3.4}\times10^6}$ $\rm{M_{\odot}}$ respectively, a star formation rate of $\rm{9.7^{+22.0}_{-6.6} M_{\odot} yr^{-1}}$, an intrinsic size of $\rm{0.54^{+0.26}_{-0.14}}$ kpc, and a luminosity-weighted age of 200$\pm$100 Myr. Strikingly, the dust production rate in this relatively young galaxy appears to be larger than that observed for equivalent, lower redshift sources. We discuss if this implies that early supernovae are more efficient dust producers and the consequences for using dust mass as a probe of earlier star formation., Comment: submitted to MNRAS, revised version after including referee's comments

Using NOEMA and ALMA 3mm line scans, we measure spectroscopic redshifts of six new dusty galaxies at 3.56, based on template IR spectrum energy distribution (SED) from known submillimeter galaxies at z=4--6. Dust SED analyses explain the photo-z overestimate from seemingly cold dust temperatures (Td) and steep Rayleigh-Jeans (RJ) slopes, providing additional examples of cold dusty galaxies impacted by the Cosmic Microwave Background (CMB). We therefore study the general properties of the enlarged sample of 10 ``cold" dusty galaxies over 3.5~4, together with the severe impact of the CMB on their RJ observables, paving the way for the diagnostics of optically thick dust in the early universe. Conventional gas mass estimates based on RJ dust continuum luminosities implicitly assume an optically thin case, overestimating gas masses by a factor of 2--3 on average in compact dusty star-forming galaxies., Comment: Published version in A&A

The 2mm Mapping Obscuration to Reionization with ALMA (MORA) Survey was designed to detect high redshift ($z\gtrsim4$), massive, dusty star-forming galaxies (DSFGs). Here we present two, likely high redshift sources, identified in the survey whose physical characteristics are consistent with a class of optical/near-infrared (OIR) invisible DSFGs found elsewhere in the literature. We first perform a rigorous analysis of all available photometric data to fit spectral energy distributions and estimate redshifts before deriving physical properties based on our findings. Our results suggest the two galaxies, called MORA-5 and MORA-9, represent two extremes of the "OIR-dark" class of DSFGs. MORA-5 ($z_{\rm phot}=4.3^{+1.5}_{-1.3}$) is a significantly more active starburst with a star-formation rate of 830$^{+340}_{-190}$M$_\odot$yr$^{-1}$ compared to MORA-9 ($z_{\rm phot}=4.3^{+1.3}_{-1.0}$) whose star-formation rate is a modest 200$^{+250}_{-60}$M$_\odot$yr$^{-1}$. Based on the stellar masses (M$_{\star}\approx10^{10-11}$M$_\odot$), space density ($n\sim(5\pm2)\times10^{-6}$Mpc$^{-3}$, which incorporates two other spectroscopically confirmed OIR-dark DSFGs in the MORA sample at $z=4.6$ and $z=5.9$), and gas depletion timescales ($, Comment: 18 pages, 7 figures, accepted for publication in ApJ

We report the discovery of a compact group of galaxies, CGG-z5, at z~5.2 in the EGS field covered by the JWST/CEERS survey. CGG-z5 was selected as the highest overdensity of galaxies at z>2 in recent JWST public surveys and it consists of six candidate members lying within a projected area of $1.5''\times3''$ (10$\times$20~kpc$^2$). All group members are HST/F435W and HST/F606W dropouts while securely detected in the JWST/NIRCam bands, yielding a narrow range of robust photometric redshifts $5.011$) at z~1. This implies that CGG-z5 could be a "proto-massive galaxy" captured during a short-lived phase of massive galaxy formation., Comment: A&A Letter in press

We present a pilot search of CO emission in three H2-absorbing, long-duration gamma-ray burst (GRB) host galaxies at z ∼ 2-3. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to target the CO(3 - 2) emission line and report nondetections for all three hosts. These are used to place limits on the host molecular gas masses, assuming a metallicity-dependent CO-to-H2 conversion factor (αCO). We find, Mmol < 3.5 × 1010M⊙ (GRB 080607), Mmol < 4.7 × 1011M⊙ (GRB 120815A), and Mmol [removed]1 with M∗ < 1010M⊙. To better quantify this we develop a simple approach to estimate the relevant αCO factor based only on the redshift and stellar mass of individual galaxies. The elevated conversion factors will make these galaxies appear CO-'dark' and difficult to detect in emission, as is the case for the majority of GRB hosts. GRB spectroscopy thus offers a complementary approach to identify low-metallicity, star-forming galaxies with abundant molecular gas reservoirs at high redshifts that are otherwise missed by current ALMA surveys. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society., KEH and PJ acknowledge support by a Project Grant (162948-051) from The Icelandic Research Fund. MN acknowledges support from ERC Advanced grant 740246 (Cosmic Gas). JPUF thanks the Carlsberg Foundation for support. The Cosmic DAWN Center is funded by the DNRF. PN and JKK acknowledge support from the French Agence Nationale de la Recherche under grant ANR 17-CE31-001101/project `HIH2' (PI: Noterdaeme). This paper makes use of the following ALMA data: ADS/JAO.ALMA#2019.1.00407.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

Context. The properties of galaxies at redshift z > 6 hold the key to our understanding of the early stages of galaxy evolution and can potentially identify the sources of the ultraviolet radiation that give rise to the epoch of reionisation. The far-infrared cooling line of [C II] at 158 μm is known to be bright and correlate with the star formation rate (SFR) of low-redshift galaxies, and hence is also suggested to be an important tracer of star formation and interstellar medium properties for very high-redshift galaxies. Aims. With the aim to study the interstellar medium properties of gravitationally lensed galaxies at z > 6, we search for [C II] and thermal dust emission in a sample of 52 z ∼ 6 galaxies observed by the ALMA Lensing Cluster Survey. Methods. We perform our analysis using LINESTACKER, stacking both [C II] and continuum emission. The target sample is selected from multiple catalogues, and the sample galaxies have spectroscopic redshift or low-uncertainty photometric redshifts (σz Results. Our analyses find no detection of either [C II] or continuum. An upper limit on L[CII] is derived, implying that [C II] remains marginally consistent for low-SFR z > 6 galaxies but likely is under-luminous compared to the local L[CII]-SFR relationship. We discuss potential biases and possible physical effects that may be the cause of the non-detection. Further, the upper limit on the dust continuum implies that less than half of the star formation is obscured.

We present the results of an integral field spectroscopy survey of a sample of dusty (ultra) luminous infrared galaxies (U/LIRGs) at 2 < z < 2.5 using KMOS on the Very Large Telescope. The sample has been drawn from Herschel deep field surveys and benefits from ancillary multiwavelength data. Our goal is to investigate the physical characteristics, kinematics, and the drivers of star formation in the galaxies whose contribution dominates the peak of the cosmic star formation density. Two-thirds of the sample are main-sequence galaxies in contrast to the starburst nature of local U/LIRGs. Our kinematic study, unique in its focus on z ∼ 2 dusty star-forming galaxies, uses the H α emission line to find that ∼40 per cent appear to be isolated discs based on the ratio of rotational velocity to the velocity dispersion, suggesting steady-state mechanisms are sufficient to power the large star formation rates (SFRs). The ratio of obscured to unobscured star formation indicates the sample of galaxies experiences less dust obscuration compared to intermediate and local counterparts, while also hosting cooler dust than local U/LIRGs. In addition to H α we detect [N II] 6583 Å in our targets and show the gas-phase metallicities do not exhibit the metal deficiency of local U/LIRGs. These results indicate that, despite their extreme IR luminosity, the underlying mechanisms driving the massive SFRs found at cosmic noon are due to scaled up disc galaxies as opposed to mergers. We want to thank the anonymous referee for their insightful comments and suggestions that improved the quality of this paper. The analysis in this paper is based on observations made with ESO Telescopes at the La Silla Paranal Observatory under run IDs: 092.B0769(A) and 097.B-0186(A). D.R., I.G.-B., and K.G. acknowledge support from STFC through grant ST/S000488/1. G.E.M. acknowledges the Villum Fonden research grant 13160 `Gas to stars, stars to dust: tracing star formation across cosmic time' and the Cosmic Dawn Center of Excellence funded by the Danish National Research Foundation under the grant No. 140. N.T. acknowledges support from STFC through grants ST/N002717/1 and ST/S001409/1. M.P.S. acknowledges support from the Comunidad de Madrid through Atracci ' on de Talento Investigador Grant 2018-T1/TIC-11035. Peerreview

We have entered an era where the gas mass estimates of distant galaxies do not rely on a single tracer but rather on an inventory of different and independent methods, much like the case for the determination of the star formation rate (SFR) of the galaxies. This is crucial as the traditional Mgas tracers, i.e. low-J CO transition lines and dust continuum emission are becoming highly uncertain as we move to higher redshifts due to metallicity and CMB effects. Here, we present a homogeneous and statistically significant investigation of the use of atomic carbon as an alternative Mgas tracer (Valentino et al.2018) and provide evidence of optically thick far-IR emission in high−z starbursts that point towards higher dust temperatures and lower dust and gas mass estimates than previously inferred (Cortzen et al.2019, submitted). Finally, we present direct observations of the effect of the CMB on the far-IR SEDs of high-z SBs, manifested by unphyscally large (β = 2.5–3.5) apparent spectral indexes in R-J tail (Jin et al. 2019, submitted).

arXiv:2103.03584v1, We use the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) project as a template to demonstrate how deep spectrophotometric surveys covering large cosmological volumes over extended fields (1–15 deg2) with a mid-IR imaging spectrometer (17–36 µm) in conjunction with deep photometry with a far-IR camera, at wavelengths which are not affected by dust extinction can answer the most crucial questions in current galaxy evolution studies. A SPICA-like mission will be able for the first time to provide an unobscured three-dimensional (3D, i.e. x, y, and redshift z) view of galaxy evolution back to an age of the universe of less than ∼ 2 Gyrs, in the mid-IR rest frame. This survey strategy will produce a full census of the Star Formation Rate (SFR) in the universe, using polycyclic aromatic hydrocarbons (PAH) bands and fine-structure ionic lines, reaching the characteristic knee of the galaxy luminosity function, where the bulk of the population is distributed, at any redshift up to z ∼ 3.5. Deep follow-up pointed spectroscopic observations with grating spectrometers onboard the satellite, across the full IR spectral range (17–210 µm), would simultaneously measure Black Hole Accretion Rate (BHAR), from high-ionisation fine-structure lines, and SFR, from PAH and low- to mid-ionisation lines in thousands of galaxies from solar to low metallicities, down to the knee of their luminosity functions. The analysis of the resulting atlas of IR spectra will reveal the physical processes at play in evolving galaxies across cosmic time, especially its heavily dust-embedded phase during the activity peak at the cosmic noon (z ∼ 1–3), through IR emission lines and features that are insensitive to the dust obscuration., LS and JAFO acknowledge financial support by the Agenzia Spaziale Italiana (ASI) under the research contract 2018-31-HH.0. AAH acknowledges support from grants PGC2018-094671-B-I00 (MCIU/AEI/FEDER,UE) and No. MDM-2017-0737 at Unidad de Excelencia María de Maeztu-Centro de Astrobiología (INTACSIC). FJC acknowledges financial support from the Spanish Ministry MCIU under project RTI2018-096686-B-C21 (MCIU/AEI/FEDER/UE), cofunded by FEDER funds and from the Agencia Estatal de Investigación, Unidad de Excelencia María de Maeztu, ref. MDM-2017-0765. HD acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities (MICIU) under the 2014 Ramón y Cajal program RYC-2014-15686 and AYA2017-84061-P, the later one co-financed by FEDER (European Regional Development Funds). AL acknowledges the support from Comunidad de Madrid through the Atracción de Talento grant 2017-T1/TIC-5213. MPS acknowledges support from the Comunidad de Madrid, Spain, through Atracción de Talento Investigador Grant 2018-T1/TIC-11035.

We present the first results from the 2mm Mapping Obscuration to Reionization (MORA) survey, the largest ALMA contiguous blank-field survey to-date with a total area of 184 sq. arcmin and the only at 2mm to search for dusty star-forming galaxies (DSFGs). We use the 13 sources detected above 5sigma to estimate the first ALMA galaxy number counts at this wavelength. These number counts are then combined with the state-of-the-art galaxy number counts at 1.2mm and 3mm and with a backward evolution model to place constraints on the evolution of the IR luminosity function and dust-obscured star formation in the last 13 billion years. Our results suggest a steep redshift evolution on the space density of DSFGs and confirm the flattening of the IR luminosity function at faint luminosities, with a slope of $\alpha_{LF} = -0.42^{+0.02}_{-0.04}$. We conclude that the dust-obscured component, which peaks at z=2-2.5, has dominated the cosmic history of star formation for the past ~12 billion years, back to z~4. At z=5, the dust-obscured star formation is estimated to be ~35% of the total star formation rate density and decreases to 25%-20% at z=6-7, implying a minor contribution of dust-enshrouded star formation in the first billion years of the Universe. With the dust-obscured star formation history constrained up to the end of the epoch of reionization, our results provide a benchmark to test galaxy formation models, to study the galaxy mass assembly history, and to understand the dust and metal enrichment of the Universe at early times., Comment: Accepted for publication in The Astrophysical Journal

We present a Spitzer/IRAC survey of H-faint ($H_{160} \gtrsim 26.4$, $, Comment: 26 pages, 10 figures, 3 tables. Accepted for publication in ApJ

We present an analysis of the chemical abundance properties of $\approx$650 star-forming galaxies at $z \approx0.6-1.8$. Using integral-field observations from the $K$-band Multi-Object Spectrograph (KMOS), we quantify the [NII]/H$\alpha$ emission-line ratio, a proxy for the gas-phase Oxygen abundance within the interstellar medium. We define the stellar mass-metallicity relation at $z \approx0.6-1.0$ and $z \approx1.2-1.8$ and analyse the correlation between the scatter in the relation and fundamental galaxy properties (e.g. H$\alpha$ star-formation rate, H$\alpha$ specific star-formation rate, rotation dominance, stellar continuum half-light radius and Hubble-type morphology). We find that for a given stellar mass, more highly star-forming, larger and irregular galaxies have lower gas-phase metallicities, which may be attributable to their lower surface mass densities and the higher gas fractions of irregular systems. We measure the radial dependence of gas-phase metallicity in the galaxies, establishing a median, beam smearing-corrected, metallicity gradient of $ \Delta Z/ \Delta R=0.002 \pm0.004$ dex kpc$^{-1}$, indicating on average there is no significant dependence on radius. The metallicity gradient of a galaxy is independent of its rest-frame optical morphology, whilst correlating with its stellar mass and specific star-formation rate, in agreement with an inside-out model of galaxy evolution, as well as its rotation dominance. We quantify the evolution of metallicity gradients, comparing the distribution of $\Delta Z/ \Delta R$ in our sample with numerical simulations and observations at $z \approx0-3$. Galaxies in our sample exhibit flatter metallicity gradients than local star-forming galaxies, in agreement with numerical models in which stellar feedback plays a crucial role redistributing metals., Comment: Accepted for publication in MNRAS. Comments welcome. 20 pages, 12 figures. Revised version with updated introduction and FMR evolution following comments

We analyse the far-infrared properties of $\sim$ 5,000 star-forming galaxies at $z, 39 pages, 21 figures, 3 tables. Accepted to ApJ July 10, 2021

In the framework of a systematic ALMA study of IR-selected main-sequence and starburst galaxies at z~1-1.7 at typical ~1" resolution, we report on the effects of mid-IR- and X-ray-detected active galactic nuclei (AGN) on the reservoirs and excitation of molecular gas in a sample of 55 objects. We find detectable nuclear activity in ~30% of the sample. The presence of dusty tori influences the IR SED of galaxies, as highlighted by the strong correlation among the AGN contribution to the total IR luminosity budget (fAGN = LIR,AGN/LIR), its hard X-ray emission, and the Rayleigh-Jeans to mid-IR (S1.2mm/S24um) observed color, with consequences on the empirical SFR estimates. Nevertheless, we find only marginal effects of AGN on the CO (J=2,4,5,7) or neutral carbon ([CI](1-0), [CI](2-1)) line luminosities and on the derived molecular gas excitation as gauged by line ratios and the full SLEDs. The [CI] and CO emission up to J=5,7 thus primarily traces the properties of the host in typical IR luminous galaxies. However, we highlight the existence of a large variety of line luminosities and ratios despite the homogeneous selection. In particular, we find a sparse group of AGN-dominated sources with the highest LIR,AGN/LIR,SFR ratios, >3, that are more luminous in CO(5-4) than what is predicted by the L'CO(5-4)-LIR,SFR relation, which might be the result of the nuclear activity. For the general population, our findings translate into AGN having minimal effects on quantities such as gas and dust fractions and SFEs. If anything, we find hints of a marginal tendency of AGN hosts to be compact at far-IR wavelengths and to display 1.8x larger dust optical depths. In general, this is consistent with a marginal impact of the nuclear activity on the gas reservoirs and star formation in average star-forming AGN hosts with LIR>5e11 Lsun, typically underrepresented in surveys of quasars and SMGs., 16 pages, 10 figures + Appendix, accepted in A&A on August 28th, 2021. The data compilation will be available on Vizier. (Minor) updates for the AGN population with respect to the data release of Valentino et al. 2020, A&A, 641, 155. For an early access, please contact the corresponding author. Abstract slightly modified to adjust to arXiv's requirements

We describe a complete, flux-density-limited sample of galaxies at redshift $0.8 < z < 1.3$ selected at 16 micron. At the selection wavelength near 8 micron rest, the observed emission comes both from dust heated by intense star formation and from active galactic nuclei (AGNs). Fitting the spectral energy distributions (SEDs) of the sample galaxies to local-galaxy templates reveals that more than half the galaxies have SEDs dominated by star formation. About one sixth of the galaxy SEDs are dominated by an AGN, and nearly all the rest of the SEDs are composite. Comparison with X-ray and far-infrared observations shows that combinations of luminosities at rest-frame 4.5 and 8 micron give good measures of both AGN luminosity and star-formation rate. The sample galaxies mostly follow the established star-forming main sequence for $z=1$ galaxies, but of the galaxies more than 0.5 dex above that main sequence, more than half have AGN-type SEDs. Similarly, the most luminous AGNs tend to have higher star-formation rates than the main sequence value. Galaxies with stellar masses $>$10$^{11}$\,\Msun\ are unlikely to host an AGN. About 1% of the sample galaxies show an SED with dust emission typical of neither star formation nor an AGN., 14 pages, 5 tables, 29 figures, ApJ accepted v2 corrects author name formatting

When the Universe was merely three billion years old, about half of massive galaxies had already formed the bulk of their stars and new star formation plummeted [1]. How galaxies quench at such early times remains a puzzle, as their dark matter halos contain large gas reservoirs [2-4]. This gas should cool efficiently, sustaining star formation over long periods [5,6]. Here we present sensitive 1.3mm wavelength observations of cold dust in six quenched galaxies in the redshift range z=1.6 to z=3.2 with stellar masses ranging from 2.5x1010M⊙ to 5x1011M⊙, which are magnified by foreground galaxy clusters. Even with factors of up to 30 in magnification, four of the six galaxies are undetected at this wavelength. We show that these quenched galaxies have extremely little dust at early times, and by proxy very little cold molecular gas. The median dust mass is

We discuss the evolution of the interstellar medium of quiescent galaxies, currently emerging from recent analyses, with the help of a simple model based on well-established empirical relations such as the stellar mass functions and the main sequence of star formation. This model is meant to describe observed quantities without making specific assumptions on the nature of quenching processes, but relying on their observable consequences. We find that the high gas fractions seen or suggested at high redshift in quiescent galaxies, and their apparent mild evolution at early times, can be mostly attributed to a progenitor effect where recently quenched galaxies with ~10% gas fractions dominate the quiescent galaxy population until z~1. In the same context, the much lower gas and dust fractions measured in local early-type galaxies are interpreted as the product of the steady depletion of their interstellar medium on a ~2 Gyr timescale, coupled with a higher fraction of more gas-exhaustive events., 7 pages, 5 figures, 2 tables (including appendices). Accepted for publication in Astronomy & Astrophysics

Star formation in half of massive galaxies was quenched by the time the Universe was 3 billion years old

In this paper, we extend the source detection in the GOODS-ALMA field (69 arcmin$^2$, rms sensitivity $\sigma$ $\simeq$ 0.18 mJy.beam$^{-1}$), to deeper levels than presented in Franco et al. (2018). Using positional information at 3.6 and 4.5 $\mu$m (from Spitzer-IRAC), we explore the presence of galaxies detected at 1.1 mm with ALMA below our original blind detection limit of 4.8-$\sigma$ at which the number of spurious sources starts to dominate over that of real sources. In this Supplementary Catalog, we find a total of 16 galaxies, including 2 galaxies with no counterpart in HST images (also known as optically-dark galaxies) down to a 5$\sigma$ limiting depth of H = 28.2 AB (HST/WFC3 F160W). This brings the total sample of GOODS-ALMA 1.1 mm sources to 35 galaxies. Galaxies in the new sample cover a wider dynamic range in redshift ($z$ = 0.65 - 4.73), are on average twice as large (1.3 vs 0.65 kpc) and and have lower stellar mass (M$_{\star}^{\rm SC}$ = 7.6$\times$10$^{10}$M$_\odot$ vs M$_{\star}^{\rm MC}$ = 1.2$\times$10$^{11}$M$_\odot$). Although exhibiting larger physical sizes, these galaxies have still far-infrared sizes significantly more compact than inferred from their optical emission. We show that the astrometry of the HST image does not only suffer from a global astrometric shift, as already discussed in previous papers, but also from local shifts. These distortions were artificially introduced in the process of building the mosaic of the GOODS-South HST image. By comparing the positions of almost 400 galaxies detected by HST, Pan-STARRS and ALMA, we create a distortion map which can be used to correct for these astrometric issues., Comment: 18 pages, 13 figures. Accepted for publication in A&A

In this paper we study the properties of the six optically dark galaxies detected in the 69 arcmin^2 GOODS-ALMA 1.1mm continuum survey. While none of them are listed in the deepest H-band based CANDELS catalog in the GOODS-South field down to H=28.16AB, we were able to de-blend two of them from their bright neighbor and measure an $H$-band flux for them. We note that AGS4 and AGS15 have H=25.23, 27.11AB respectively. Their extreme proximity (0.50", 0.27") to a bright optical source and their extreme faintness prevented them from being included in the H-band catalog. We present the spectroscopic scan follow-up of five of the six sources with ALMA band 4. All are detected in the 2mm continuum with signal-to-noise ratios higher than eight. One emission line is detected in AGS4 (��_{obs} =151.44GHz with a S/N=8.58) and AGS17 (��_{obs} =154.78GHz with a S/N=10.23), which we interpret in both cases as being due to the CO(6-5) line at z^{AGS4}_{spec}=3.556 and z^{AGS4}_{spec}=3.467, respectively. These redshifts match both the probability distribution of the photometric redshifts derived from the UV to near-infrared spectral energy distributions (SEDs) and the far-infrared SEDs for typical dust temperatures of galaxies at these redshifts. We present evidence that nearly 70% (4/6 of galaxies) of the optically dark galaxies belong to the same overdensity of galaxies at z~3.5. overdensity The most massive one, AGS24 (M_{\star} = 10^{11.32^{+0.02}_{-0.19}} M_{\odot}), is the most massive galaxy without an active galactic nucleus (AGN) at $z$\,>\,3 in the GOODS-ALMA field. It falls in the very center of the peak of the galaxy surface density, which suggests that the surrounding overdensity is a proto-cluster in the process of virialization and that AGS24 is the candidate progenitor of the future brightest cluster galaxy (BCG)., 17 pages, 13 figures, 3 tables, accepted by A&A

We present new observations, carried out with IRAM NOEMA, of the atomic neutral carbon transitions [CI](1-0) at 492 GHz and [CI](2-1) at 809 GHz of GN20, a well-studied star-bursting galaxy at $z=4.05$. The high luminosity line ratio [CI](2-1)/[CI](1-0) implies an excitation temperature of $48^{+14}_{-9}$ K, which is significantly higher than the apparent dust temperature of $T_{\rm d}=33\pm2$ K ($\beta=1.9$) derived under the common assumption of an optically thin far-infrared dust emission, but fully consistent with $T_{\rm d}=52\pm5$ K of a general opacity model where the optical depth ($\tau$) reaches unity at a wavelength of $\lambda_0=170\pm23$ $\mu$m. Moreover, the general opacity solution returns a factor of $\sim 2\times$ lower dust mass and, hence, a lower molecular gas mass for a fixed gas-to-dust ratio, than with the optically thin dust model. The derived properties of GN20 thus provide an appealing solution to the puzzling discovery of starbursts appearing colder than main-sequence galaxies above $z>2.5$, in addition to a lower dust-to-stellar mass ratio that approaches the physical value predicted for starburst galaxies., Comment: Comments: 6 pages, 4 figures, accepted for publication in Astronomy and Astrophysics Letters on February 4th 2020

Steinhardt et al., arXiv:2001.09999v2, The Beyond Ultra-deep Frontier Fields and Legacy Observations (BUFFALO) is a 101 orbit + 101 parallel Cycle 25 Hubble Space Telescope (HST) Treasury program taking data from 2018 to 2020. BUFFALO will expand existing coverage of the Hubble Frontier Fields (HFF) in Wide Field Camera 3/IR F105W, F125W, and F160W and Advanced Camera for Surveys/WFC F606W and F814W around each of the six HFF clusters and flanking fields. This additional area has not been observed by HST but is already covered by deep multiwavelength data sets, including Spitzer and Chandra. As with the original HFF program, BUFFALO is designed to take advantage of gravitational lensing from massive clusters to simultaneously find high-redshift galaxies that would otherwise lie below HST detection limits and model foreground clusters to study the properties of dark matter and galaxy assembly. The expanded area will provide the first opportunity to study both cosmic variance at high redshift and galaxy assembly in the outskirts of the large HFF clusters. Five additional orbits are reserved for transient follow-up. BUFFALO data including mosaics, value-added catalogs, and cluster mass distribution models will be released via MAST on a regular basis as the observations and analysis are completed for the six individual clusters., C.S. acknowledges support from the ERC Consolidator Grant funding scheme (project ConTExT, grant No. 648179). Y.M.B. acknowledges funding from the EU Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement 747645 (ClusterGal). J.M.D. acknowledges the support of project PGC2018-101814-B-100 (MCIU/AEI/MINECO/FEDER, UE), Ministerio de Ciencia, Investigación y Universidades.

We present a method for recovering the intrinsic (extinction-corrected) luminosity of the 11.2 micron PAH band in galaxy spectra. Using 105 high S/N Spitzer/IRS spectra of star-forming galaxies, we show that the equivalent width ratio of the 12.7 and 11.2 micron PAH bands is independent on the optical depth, with small dispersion of ~5% indicative of a nearly constant intrinsic flux ratio R_int = (f_12.7/f_11.2)_int = 0.377 +/- 0.020. Conversely, the observed flux ratio, R_obs = (f_12.7/f_11.2)_obs strongly correlates with the silicate strength (S_sil) confirming that differences in R_obs reflect variation in the optical depth. The relation between R_obs and S_sil reproduces predictions for the Galactic Centre extinction law but disagrees with other laws. We calibrate the total extinction affecting the 11.2 micron PAH from R_obs, which we apply to another sample of 215 galaxies with accurate measurements of the total infrared luminosity (L_IR) to investigate the impact of extinction on L_11.2/L_IR. Correlation between L_11.2/L_IR and R_obs independently on L_IR suggests that increased extinction explains the well known decrease in the average L_11.2/L_IR at high L_IR. The extinction-corrected L_11.2 is proportional to L_IR in the range L_IR/L_sun = 10^9--10^13. These results consolidate L_11.2 as a robust tracer of star formation in galaxies., Comment: 14 pages, 9 figures, 2 tables. Accepted for publication in MNRAS

We thoroughly explore the properties of (sub)-millimeter (mm) selected galaxies (SMGs) in the Shark semi-analytic model of galaxy formation. Compared to observations, the predicted number counts at wavelengths (lambda) 0.6-2mm and redshift distributions at 0.1-2mm, agree well. At the bright end (>1mJy), Shark galaxies are a mix of mergers and disk instabilities. These galaxies display a stacked FUV-to-FIR spectrum that agrees well with observations. We predict that current optical/NIR surveys are deep enough to detect bright (>1mJy) lambda=0.85-2mm-selected galaxies at z0.01$mJy. We predict SMG's disks contribute significantly (negligibly) to the rest-frame UV (IR). We investigate the 01mJy lambda=0.85-2mm-selected galaxies finding their: (i) stellar masses are $>10^{10.2}M_{\odot}$, with the 2mm ones tracing the most massive galaxies ($>10^{11}M_{\odot}$); (ii) specific star formation rates (SFR) are mildly (~3-10x) above the main sequence (MS); (iii) host halo masses are $\gtrsim 10^{12.3}M_{\odot}$, with 2mm galaxies tracing the most massive halos (proto-clusters); (iv) SMGs have lower dust masses ($\approx 10^{8}M_{\odot}$), higher dust temperatures ($\approx 40-45$K) and higher rest-frame V-band attenuation (>1.5) than MS galaxies; (v) sizes decrease with redshift, from 4kpc at z=1 to 1$mJy sources peak at 4->3. Finally, we study the contribution of SMGs to the molecular gas and cosmic SFR density at 01mJy sources make a negligible contribution at z>3 and z>5, respectively, suggesting current observations have unveiled the majority of the star formation at 0, Comment: Final version accepted for publication in MNRAS. 28 pages, 22 of main text and figures

We present the detection of multiple CO line transitions with ALMA in a few tens of infrared-selected galaxies on and above the main sequence at z=1.1-1.7. We reliably detected the emission of CO(5-4), CO(2-1), and CO(7-6)+[CI](2-1) in 50, 33, and 13 galaxies, respectively, and we complemented this information with available CO(4-3) and [CI](1-0) fluxes for part of the sample, and modeling of the optical-to-mm SEDs. We retrieve a quasi-linear relation between LIR and CO(5-4) or CO(7-6) for main-sequence galaxies and starbursts, corroborating the hypothesis that these transitions can be used as SFR tracers. We find the CO excitation to steadily increase as a function of the star formation efficiency, the mean intensity of the radiation field warming the dust, the surface density of SFR, and, less distinctly, with the distance from the main sequence. This adds to the tentative evidence for higher excitation of the CO+[CI] SLED of starbursts relative to that for main-sequence objects, where the dust opacities play a minor role in shaping the high-J CO transitions in our sample. However, the distinction between the average SLED of upper main-sequence and starburst galaxies is blurred, driven by a wide variety of intrinsic shapes. LVG radiative transfer modeling demonstrates the existence of a highly excited component that elevates the CO SLED of high-redshift main-sequence and starbursting galaxies above the typical values observed in the disk of the Milky Way. This excited component is dense and it encloses ~50% of the total molecular gas mass in main-sequence objects. We interpret the observed trends involving the CO excitation as mainly driven by a combination of large SFRs and compact sizes, naturally connected with enhanced dense molecular gas fractions and higher dust and gas temperatures, due to increasing UV radiation fields, cosmic ray rates, and dust/gas coupling. [Abridged], Comment: 18 pages, 9 figures + Appendix, accepted in A&A. The data compilation will be released as a .fits table on the journal's website. For an early access, please contact the corresponding author. The plots of spectra and far-infrared SEDs will be available on the journal's website and temporarily at this link: https://bit.ly/spectra_and_seds_valentino_2020c

We report two secure ($z=3.775, 4.012$) and one tentative ($z\approx3.767$) spectroscopic confirmations of massive and quiescent galaxies through $K$-band observations with Keck/MOSFIRE and VLT/X-Shooter. The stellar continuum emission, the absence of strong nebular emission lines and the lack of significant far-infrared detections confirm the passive nature of these objects, disfavoring the alternative solution of low-redshift dusty star-forming interlopers. We derive stellar masses of $\mathrm{log}(M_{\star}/M_\odot)\sim11$ and ongoing star formation rates placing these galaxies $\gtrsim 1-2$ dex below the main sequence at their redshifts. The adopted parametrization of the star formation history suggests that these sources experienced a strong ($\langle \rm SFR \rangle \sim 1200-3500\,M_\odot\,\mathrm{yr}^{-1}$) and short ($\sim 50$ Myr) burst of star formation, peaking $\sim 150-500$ Myr before the time of observation, all properties reminiscent of the characteristics of sub-millimeter galaxies (SMGs) at $z>4$. We investigate this connection by comparing the comoving number densities and the properties of these two populations. We find a fair agreement only with the deepest sub-mm surveys detecting not only the most extreme starbursts, but also more normal galaxies. We support these findings by further exploring the Illustris-TNG cosmological simulation, retrieving populations of both fully quenched massive galaxies at $z\sim3-4$ and SMGs at $z\sim4-5$, with number densities and properties in agreement with the observations at $z\sim3$, but in increasing tension at higher redshift. Nevertheless, as suggested by the observations, not all the progenitors of quiescent galaxies at these redshifts shine as bright SMGs in their past and, similarly, not all bright SMGs quench by $z\sim3$, both fractions depending on the threshold assumed to define the SMGs themselves., 20 pages (+appendix), 11 figures, accepted for publication in the Astrophysical Journal (ApJ). This work comes with a companion letter by Tanaka, Valentino, Toft et al. 2019, ApJL, 885, L34

We report the discovery of a Multi Unit Spectroscopic Explorer (MUSE) galaxy group at z=4.32 lensed by the massive galaxy cluster ACT-CL J0102-4915 (aka El Gordo) at z=0.87, associated with a 1.2 mm source which is at a 2.07+/-0.88 kpc projected distance from one of the group galaxies. Three images of the whole system appear in the image plane. The 1.2 mm source has been detected within the Atacama Large Millimetre/submillimetre Array (ALMA) Lensing Cluster Survey (ALCS). As this ALMA source is undetected at wavelengths lambda < 2 microns, its redshift cannot be independently determined, however, the three lensing components indicate that it belongs to the same galaxy group at z=4.32. The four members of the MUSE galaxy group have low to intermediate stellar masses (~ 10^7-10^{10} Msun) and star formation rates (SFRs) of 0.4-24 Msun/yr, resulting in high specific SFRs (sSFRs) for two of them, which suggest that these galaxies are growing fast (with stellar-mass doubling times of only ~ 2x10^7 years). This high incidence of starburst galaxies is likely a consequence of interactions within the galaxy group, which is compact and has high velocity dispersion. Based on the magnification-corrected sub-/millimetre continuum flux density and estimated stellar mass, we infer that the ALMA source is classified as an ordinary ultra-luminous infrared galaxy (with associated dust-obscured SFR~200-300 Msun/yr) and lies on the star-formation main sequence. This reported case of an ALMA/MUSE group association suggests that some presumably isolated ALMA sources are in fact signposts of richer star-forming environments at high redshifts., 13 pages including 7 figures and 1 table. Accepted for publication at the ApJ. Minor changes with respect to version 1. Figure 6 has been expanded to broaden comparison with the literature

International audience; We present a detailed analysis of a large sample of spectroscopically confirmed massive quiescent galaxies (MQGs; log(M */M ⊙) ∼ 11.5) at z ≳ 2. This sample comprises 15 galaxies selected in the COSMOS and UDS fields by their bright K-band magnitudes and followed up with Very Large Telescope (VLT) X-shooter spectroscopy and Hubble Space Telescope (HST)/WFC3 H F160W imaging. These observations allow us to unambiguously confirm their redshifts, ascertain their quiescent nature and stellar ages, and reliably assess their internal kinematics and effective radii. We find that these galaxies are compact, consistent with the high-mass end of the stellar mass-size relation for quiescent galaxies at z = 2. Moreover, the distribution of the measured stellar velocity dispersions of the sample is consistent with the most massive local early-type galaxies from the MASSIVE Survey, showing that evolution in these galaxies is dominated by changes in size. The HST images reveal, as surprisingly high, that 40% of the sample has tidal features suggestive of mergers and companions in close proximity, including three galaxies experiencing ongoing major mergers. The absence of velocity dispersion evolution from z = 2 to 0, coupled with a doubling of the stellar mass, with a factor of 4 size increase and the observed disturbed stellar morphologies, supports dry minor mergers as the primary drivers of the evolution of the MQGs over the last 10 billion yr.

Observations of cold molecular gas reservoirs are critical for understanding the shutdown of star formation in massive galaxies. While dust continuum is an efficient and affordable tracer, this method relies upon the assumption of a "normal" molecular-gas to dust mass ratio, $\delta_{\mathrm{GDR}}$, typically of order one hundred. Recent null detections of quiescent galaxies in deep dust continuum observations support a picture where the cold gas and dust has been rapidly depleted or expelled. In this work, we present another viable explanation: a significant fraction of galaxies with low star formation per unit stellar mass are predicted to have extreme $\delta_{\mathrm{GDR}}$ ratios. We show that simulated massive quiescent galaxies at $0 < z < 3$ in the \textsc{simba} cosmological simulations have $\delta_{\mathrm{GDR}}$ values that extend $>$4 orders of magnitude. The dust in most simulated quiescent galaxies is destroyed significantly more rapidly than the molecular gas depletes, and cannot be replenished. The transition from star-forming to quiescent halts dust formation via star formation processes, with dust subsequently destroyed by supernova shocks and thermal sputtering of dust grains embedded in hot plasma. After this point, the dust growth rate in the models is not sufficient to overcome the loss of $>$3 orders of magnitude in dust mass to return to normal values of $\delta_{\mathrm{GDR}}$ despite having high metallicity. Our results indicate that it is not straight forward to use a single observational indicator to robustly pre-select exotic versus normal ratios. These simulations make strong predictions that can be tested with millimeter facilities., Comment: 9 pages, 5 figures, version accepted for publication in the Astrophysical Journal Letters

We present an analysis of the gas outflow energetics of 529 main-sequence star-forming galaxies at z~1 using KMOS observations of the broad, underlying H-alpha and forbidden lines of [N II] and [S II]. Based on the stacked spectra for a sample with median star-formation rates and stellar masses of SFR ~ 7 Mo/yr and M* = (1.0+/-0.1)x10^10 Mo respectively, we derive a typical mass outflow rate of dM/dt = 1-4 Mo/yr and a mass loading of dM/dt/SFR = 0.2--0.4. The mass loading of the wind does not show a strong trend with star-formation rate over the range SFR ~ 2--20 Mo/yr, although we identify a trend with stellar mass such that dM/dt/SFR ~ M*^(0.26+/-0.07). Finally, we find that the line width of the broad H-alpha increases with disk circular velocity with a sub-linear scaling relation FWHM_broad ~ v^(0.21+/-0.05). As a result of this behavior, in the lowest mass galaxies (M* < 10^10 Mo), a significant fraction of the outflowing gas should have sufficient velocity to escape the gravitational potential of the halo whilst in the highest mass galaxies (M* > 10^10 Mo) most of the gas will be retained, flowing back on to the galaxy disk at later times., Accepted for publication in MNRAS (14 pages, 8 figures). Data release: Datacubes and data products from KROSS are now available at http://astro.dur.ac.uk/KROSS/data.html

The extreme infrared (IR) luminosity of local luminous and ultra-luminous IR galaxies (U/LIRGs; 11 < log LIR /Lsun < 12 and log LIR /Lsun > 12, respectively) is mainly powered by star-formation processes triggered by mergers or interactions. While U/LIRGs are rare locally, at z > 1, they become more common, they dominate the star-formation rate (SFR) density, and a fraction of them are found to be normal disk galaxies. Therefore, there must be an evolution of the mechanism triggering these intense starbursts with redshift. To investigate this evolution, we present new optical SWIFT integral field spectroscopic H{\alpha}+[NII] observations of a sample of 9 intermediate-z (0.2 < z < 0.4) U/LIRG systems selected from Herschel 250{\mu}m observations. The main results are the following: (a) the ratios between the velocity dispersion and the rotation curve amplitude indicate that 10-25% (1-2 out of 8) might be compatible with being isolated disks while the remaining objects are interacting/merging systems; (b) the ratio between un-obscured and obscured SFR traced by H{\alpha} and LIR, respectively, is similar in both local and these intermediate-z U/LIRGs; and (c) the ratio between 250{\mu}m and the total IR luminosities of these intermediate-z U/LIRGs is higher than that of local U/LIRGs with the same LIR . This indicates a reduced dust temperature in these intermediate-z U/LIRGs. This, together with their already measured enhanced molecular gas content, suggests that the interstellar medium conditions are different in our sample of intermediate-z galaxies when compared to local U/LIRGs., Comment: Accepted for publication in MNRAS

We construct Tully–Fisher relations (TFRs), from large samples of galaxies with spatially resolved H α emission maps from the K-band Multi-Object Spectrograph (KMOS) Redshift One Spectroscopic Survey (KROSS) at z ≈ 1. We compare these to data from the Sydney-Australian-Astronomical-Observatory Multi-object Integral-Field Spectrograph (SAMI) Galaxy Survey at z ≈ 0. We stringently match the data quality of the latter to the former, and apply identical analysis methods and sub-sample selection criteria to both to conduct a direct comparison of the absolute K-band magnitude and stellar mass TFRs at z ≈ 1 and 0. We find that matching the quality of the SAMI data to that of KROSS results in TFRs that differ significantly in slope, zero-point, and (sometimes) scatter in comparison to the corresponding original SAMI relations. These differences are in every case as large as or larger than the differences between the KROSS z ≈ 1 and matched SAMI z ≈ 0 relations. Accounting for these differences, we compare the TFRs at z ≈ 1 and 0. For disc-like, star-forming galaxies we find no significant difference in the TFR zero-points between the two epochs. This suggests the growth of stellar mass and dark matter in these types of galaxies is intimately linked over this ≈8 Gyr period.

We present the first stellar velocity dispersion measurement of a massive quenching galaxy at z=4.01. The galaxy is first identified as a massive z>~4 galaxy with suppressed star formation from photometric redshifts based on deep multi-band data in the UKIDSS Ultra Deep Survey field. A follow-up spectroscopic observation with MOSFIRE on Keck revealed strong multiple absorption features, which are identified as Balmer absorption lines, giving a secure redshift of z=4.01. Thanks to the high S/N of the spectrum, we are able to estimate the stellar velocity dispersion, sigma=268+/-59 km/s. This velocity dispersion is consistent with that of massive galaxies today, implying no significant evolution in stellar velocity dispersion over the last 12 Gyr. Based on an upper limit on its physical size from deep optical images (r_eff, Published in the Astrophysical Journal letters. Fixed an error in dynamical mass