Abstract
We make use of ultra-deep 3 GHz Karl G. Jansky Very Large Array (VLA) observations of the COSMOS field from the multiband COSMOS-XS survey to infer radio luminosity functions (LFs) of ...star-forming galaxies (SFGs). Using ∼1300 SFGs with redshifts out to
z
∼ 4.6, and fixing the faint and bright end shape of the radio LF to the local values, we find a strong redshift trend that can be fitted by pure luminosity evolution with the luminosity parameter given by
α
L
∝ (3.40 ± 0.11) − (0.48 ± 0.06)
z
. We then combine the ultra-deep COSMOS-XS data set with the shallower VLA-COSMOS 3 GHz large project data set over the wider COSMOS field in order to fit for joint density+luminosity evolution, finding evidence for significant density evolution. By comparing the radio LFs to the observed far-infrared and ultraviolet (UV) LFs, we find evidence of a significant underestimation of the UV LF by 22% ± 14% at high redshift (3.3 <
z
< 4.6, integrated down to
0.03
L
z
=
3
⋆
). We derive the cosmic star formation rate density (SFRD) by integrating the fitted radio LFs and find that the SFRD rises up to
z
∼ 1.8 and then declines more rapidly than previous radio-based estimates. A direct comparison between the radio SFRD and a recent UV-based SFRD, where we integrate both LFs down to a consistent limit (
0.038
L
z
=
3
⋆
), reveals that the discrepancy between the radio and UV LFs translates to a significant (∼1 dex) discrepancy in the derived SFRD at
z
> 3, even assuming the latest dust corrections and without accounting for optically dark sources.
One of the main achievements in modern cosmology is the so-called unified model, which successfully describes most classes of active galactic nuclei (AGNs) within a single physical scheme. However, ...there is a particular class of radio-luminous AGNs that presently cannot be explained within this framework--the 'low-excitation' radio AGN (LERAGN). Recently, a scenario has been put forward which predicts that LERAGNs and their regular 'high-excitation' radio AGN (HERAGN) counterparts represent different (red sequence versus green valley) phases of galaxy evolution. These different evolutionary states are also expected to be reflected in their host galaxy properties, in particular their cold gas content. To test this, here we present CO(1->0) observations toward a sample of 11 of these systems conducted with CARMA. Combining our observations with literature data, we derive molecular gas masses (or upper limits) for a complete, representative, sample of 21 z < 0.1 radio AGNs. Our results yield that HERAGNs on average have a factor of ~7 higher gas masses than LERAGNs. We also infer younger stellar ages, lower stellar, halo, and central supermassive black masses, as well as higher black hole accretion efficiencies in HERAGNs relative to LERAGNs. These findings support the idea that HERAGNs and LERAGNs form two physically distinct populations of galaxies that reflect different stages of massive galaxy buildup.
Using the Atacama Large Millimeter/submillimeter Array (ALMA), we report high angular-resolution observations of the redshift z = 3.63 galaxy H-ATLAS J083051.0+013224 (G09v1.97), one of the most ...luminous strongly lensed galaxies discovered by the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). We present 0.″2−0.″4 0 . ″ 2 − 0 . ″ 4 $ 0{{\overset{\prime\prime}{.}}}2{-}0{{\overset{\prime\prime}{.}}}4 $ resolution images of the rest-frame 188 and 419 μm dust continuum and the CO(6–5), H2O(211−202), and Jup = 2 H2O+ line emission. We also report the detection of H2O(211−202) in this source. The dust continuum and molecular gas emission are resolved into a nearly complete ∼1.″5 ∼ 1 . ″ 5 $ {\sim}1{{\overset{\prime\prime}{.}}}5 $ diameter Einstein ring plus a weaker image in the center, which is caused by a special dual deflector lensing configuration. The observed line profiles of the CO(6–5), H2O(211−202), and Jup = 2 H2O+ lines are strikingly similar. In the source plane, we reconstruct the dust continuum images and the spectral cubes of the CO, H2O, and H2O+ line emission at sub-kiloparsec scales. The reconstructed dust emission in the source plane is dominated by a compact disk with an effective radius of 0.7 ± 0.1 kpc plus an overlapping extended disk with a radius twice as large. While the average magnification for the dust continuum is μ ∼ 10−11, the magnification of the line emission varies from 5 to 22 across different velocity components. The line emission of CO(6–5), H2O(211−202), and H2O+ have similar spatial and kinematic distributions. The molecular gas and dust content reveal that G09v1.97 is a gas-rich major merger in its pre-coalescence phase, with a total molecular gas mass of ∼1011 M⊙. Both of the merging companions are intrinsically ultra-luminous infrared galaxies (ULIRGs) with infrared luminosities LIR reaching ≳4 × 1012 L⊙, and the total LIR of G09v1.97 is (1.4 ± 0.7)×1013 L⊙. The approaching southern galaxy (dominating from V = −400 to −150 km s−1 relative to the systemic velocity) shows no obvious kinematic structure with a semi-major half-light radius of as = 0.4 kpc, while the receding galaxy (0 to 350 km s−1) resembles an as = 1.2 kpc rotating disk. The two galaxies are separated by a projected distance of 1.3 kpc, bridged by weak line emission (−150 to 0 km s−1) that is co-spatially located with the cold dust emission peak, suggesting a large amount of cold interstellar medium (ISM) in the interacting region. As one of the most luminous star-forming dusty high-redshift galaxies, G09v1.97 is an exceptional source for understanding the ISM in gas-rich starbursting major merging systems at high redshift.
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ABSTRACT
We have carried out Hubble Space Telescope (HST) snapshot observations at 1.1 μm of 281 candidate strongly lensed galaxies identified in the wide-area extragalactic surveys conducted with ...the Herschel Space Observatory. Our candidates comprise systems with flux densities at $500\, \mu$m, S500 ≥ 80 mJy. We model and subtract the surface brightness distribution for 130 systems, where we identify a candidate for the foreground lens candidate. After combining visual inspection, archival high-resolution observations, and lens subtraction, we divide the systems into different classes according to their lensing likelihood. We confirm 65 systems to be lensed. Of these, 30 are new discoveries. We successfully perform lens modelling and source reconstruction on 23 systems, where the foreground lenses are isolated galaxies and the background sources are detected in the HST images. All the systems are successfully modelled as a singular isothermal ellipsoid. The Einstein radii of the lenses and the magnifications of the background sources are consistent with previous studies. However, the background source circularized radii (between 0.34 and 1.30 kpc) are ∼3 times smaller than the ones measured in the sub-millimetre/millimetre for a similarly selected and partially overlapping sample. We compare our lenses with those in the Sloan Lens Advanced Camera for Surveys (ACS) Survey confirming that our lens-independent selection is more effective at picking up fainter and diffuse galaxies and group lenses. This sample represents the first step towards characterizing the near-infrared properties and stellar masses of the gravitationally lensed dusty star-forming galaxies.
We present super(12)CO(J= 110) observations of the high-redshift quasi-stellar objects (QSOs) BR 1202-0725 (z =4.69), PSS J2322+1944 (z = 4.12), and APM 08279+5255 (z = 3.91)using the NRAO Green Bank ...Telescope (GBT) and the MPIfR Effelsberg 100 m telescope. We detect, for the first time, the CO ground-level transition in BR 1202-0725. For PSS J2322+1944 and APM 08279+5255, our observations result in line fluxes that are consistent with previous NRAO Very Large Array (VLA) observations, but they reveal the full line profiles. We report a typical lensing-corrected velocity-integrated intrinsic super(12)CO(J = 110 line luminosity of L super('CO)=5 x 10 super(10) K km s super(-1) pc super(2) and a typical total H sub(2) mass of M(H sub(2)) = 4 x 10 super(10) M sub( )for the sources in our sample. The CO/FIR luminosity ratios of these high-z sources follow the same trend as seen for low-z galaxies, leading to a combined solution of log L sub(FIR) = (1.39 c 0.05) log L sub(CO) -1.76. It has previously been suggested that the molecular gas reservoirs in some quasar host galaxies may exhibit luminous, extended super(12)CO(J = 110) components that are not observed in the higher J CO transitions. Using the line profiles and the total intensities of our observations and large velocity gradient (LVG) models based on previous results for higher JCO transitions, we derive that emission from all CO transitions is described well by a single gas component in which all molecular gas is concentrated in a compact nuclear region. Thus, our observations and models show no indication of aluminous extended, low surface brightness molecular gas component in any of the high-redshift QSOs in our sample. If such extended components exist, their contribution to the overall luminosity is limited to at most 30%.
Abstract
We present the results of combined deep Keck/NIRC2,
HST
/WFC3 near-infrared, and
Herschel
far-infrared observations of an extremely star-forming dusty lensed galaxy identified from the
...Herschel
Astrophysical Terahertz Large Area Survey (
H
-ATLAS J133542.9+300401). The galaxy is gravitationally lensed by a massive
WISE
-identified galaxy cluster at
z
∼ 1. The lensed galaxy is spectroscopically confirmed at
z
= 2.685 from detection of
by GBT and from detection of
obtained with CARMA. We use the combined spectroscopic and imaging observations to construct a detailed model of the background dusty lensed submillimeter galaxy (SMG), which allows us to study the source plane properties of the target. The best-fit lens model provides magnifications of
μ
star
= 2.10 ± 0.11 and
μ
dust
= 2.02 ± 0.06 for the stellar and dust components, respectively. Multiband data yield a magnification-corrected star formation rate of 1900(±200)
M
⊙
yr
−1
and a stellar mass of
, consistent with a main sequence of star formation at
z
∼ 2.6. The CO observations yield a molecular gas mass of 8.3(±1.0) × 10
10
M
⊙
, similar to the most massive star-forming galaxies, which together with the high star formation efficiency, are responsible for the intense observed star formation rates. The lensed SMG has a very short gas depletion timescale of ∼40 Myr. The high stellar mass and small gas fractions observed indicate that the lensed SMG likely has already formed most of its stellar mass and could be a progenitor of the most massive elliptical galaxies found in the local universe.
ABSTRACT
We present results of dust continuum and C ii$\, 158\, {\rm \mu m}$ emission line observations of a remarkably UV luminous (MUV = −21.6) galaxy at z = 10.603: GN-z11. Using the Northern ...Extended Millimeter Array (NOEMA), observations have been carried out over multiple observing cycles. We achieved a high sensitivity resulting in a $\lambda _{\rm rest}=160\, {\rm \mu m}$ continuum $1\, \sigma$ sensitivity of $13.0\, \rm {\mu Jy \, beam}^{ -1}$ and a C ii emission line $1\, \sigma$ sensitivity of $31\, \rm {mJy\, beam^{ -1}\, km \, s}^{ -1}$ using $50\, \rm {km \, s}^{ -1}$ binning with a $\sim 2\, {\rm arcsec}$ synthesized beam. Neither dust continuum nor C ii$\, 158\, {\rm \mu m}$ line emission are detected at the expected frequency of νC ii$= 163.791\, \rm {GHz}$ and the sky location of GN-z11. The upper limits show that GN-z11 is neither luminous in LIR nor LC ii, with a dust mass $3\, \sigma$ limit of ${\rm log}\, (M_{\rm dust}/{\rm {\rm M}_{\odot }}) \, \lt\, 6.5-6.9$ and with a C ii based molecular gas mass $3\, \sigma$ limit of log (Mmol, C ii$/{\rm {\rm M}_{\odot }}) \, \lt \, 9.3$. Together with radiative transfer calculations, we also investigated the possible cause of the dust poor nature of the GN-z11 showed by the blue colour in the UV continuum of GN-z11 (βUV = −2.4), and found that ≳3 × deeper observations are crucial to study dust production at very high-redshift. Nevertheless, our observations show the crucial role of deep mm/submm observations of very high-redshift galaxies to constrain multiple phases in the interstellar medium.
Using the IRAM NOrthern Extended Millimetre Array (NOEMA), we conducted a Large Programme (z-GAL) to measure redshifts for 126 bright galaxies detected in the Herschel Astrophysical Large Area Survey ...(H-ATLAS), the HerMES Large Mode Survey (HeLMS), and the Herschel Stripe 82 (HerS) Survey. We report reliable spectroscopic redshifts for a total of 124 of the Herschel-selected galaxies. The redshifts are estimated from scans of the 3 and 2-mm bands (and, for one source, the 1-mm band), covering up to 31 GHz in each band, and are based on the detection of at least two emission lines. Together with the Pilot Programme, where 11 sources had their spectroscopic redshifts measured, our survey has derived precise redshifts for 135 bright Herschel-selected galaxies, making it the largest sample of high-z galaxies with robust redshifts to date. Most emission lines detected are from 12 CO (mainly from J = 2-1 to 5-4), with some sources seen in CI and H 2 O emission lines. The spectroscopic redshifts are in the range 0.8 < z < 6.55 with a median value of z = 2.56 ± 0.10, centred on the peak epoch of galaxy formation. The linewidths of the sources are large, with a mean value for the full width at half maximum ∆V of 590 ± 25 km s −1 and with 35% of the sources having widths of 700 km s −1 < ∆V < 1800 km s −1. Most of the sources are unresolved or barely resolved on scales of ∼2 to 3 (or linear sizes of ∼15−25 kpc, unlensed). Some fields reveal double or multiple sources in line emission and the underlying dust continuum and, in some cases, sources at different redshifts. Taking these sources into account, there are, in total, 165 individual sources with robust spectroscopic redshifts, including lensed galaxies, binary systems, and over-densities. This paper presents an overview of the z-GAL survey and provides the observed properties of the emission lines, the derived spectroscopic redshifts, and a catalogue of the entire sample. The catalogue includes, for each source, the combined continuum and emission lines' maps together with the spectra for each of the detected emission lines. The data presented here will serve as a foundation for the other z-GAL papers in this series reporting on the dust emission, the molecular and atomic gas properties, and a detailed analysis of the nature of the sources. Comparisons are made with other spectroscopic surveys of high-z galaxies and future prospects, including dedicated follow-up observations based on these redshift measurements, are outlined.
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We used the Plateau de Bure Interferometer (PdBI) to map a sample of 15 sub-millimetre galaxies (SMGs) in the COSMOS field at the wavelength of 1.3 mm. The target SMGs were originally discovered in ...the James Clerk Maxwell Telescope (JCMT)/AzTEC 1.1 mm continuum survey at S/N1.1 mm = 4-4.5. This paper presents, for the first time, interferometric millimetre-wavelength observations of these sources. To study the overall multiplicity and redshift distribution of flux-limited samples of SMGs we combined these sources with the 15 brightest JCMT/AzTEC SMGs detected at 1.1 mm, AzTEC1-15, and studied previously. We find that the median redshift for the 15 brightest JCMT/AzTEC SMGs is consistent with that for AzTEC16-30. This conforms to recent observational findings that SMGs do not exhibit any significant trend between the redshift and (sub)mm flux density. For the combined AzTEC1-30 sample we derive a median redshift of = 3.17 + or - 0.27, consistent with previous results based on mm-selected samples.
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We investigate the physical properties of a sample of six submillimeter galaxies (SMGs) in the COSMOS field, spectroscopically confirmed to lie at redshifts z> 4. While the redshifts for four of ...these SMGs were previously known, we present here two newly discovered zspec> 4 SMGs. For our analysis we employ the rich (X-ray to radio) COSMOS multi-wavelength datasets. In particular, we use new data from the Giant Meterwave Radio Telescope (GMRT) 325 MHz and 3 GHz Jansky Very Large Array (VLA) to probe the rest-frame 1.4 GHz emission at z = 4, and to estimate the sizes of the star formation regions of these sources, respectively. We find that only oneSMG is clearly resolved at a resolution of 0''̣6 × 0''̣7 at 3 GHz, two may be marginally resolved, while the remaining three SMGs are unresolved at this resolution. Combining this with sizes from high-resolution (sub-)mm observations available in the literature for AzTEC 1 and AzTEC 3 we infer a median radio-emitting size for our z> 4 SMGs of (0''̣63 ± 0''̣12) × (0''̣35 ± 0''̣05) or 4.1 × 2.3 kpc2 (major × minor axis; assuming z = 4.5) or lower if we take the two marginally resolved SMGs as unresolved. This is consistent with the sizes of star formation regions in lower-redshift SMGs, and local normal galaxies, yet higher than the sizes of star formation regions of local ultraluminous infrared galaxies (ULIRGs). Our SMG sample consists of a fair mix of compact and more clumpy systems with multiple, perhaps merging, components. With an average formation time of ~280 Myr, as derived through modeling of the UV IR spectral energy distributions, the studied SMGs are young systems. The average stellar mass, dust temperature, and IR luminosity we derive are M⋆ ~ 1.4 × 1011 M⊙, Tdust ~ 43 K, and LIR ~ 1.3 × 1013L⊙, respectively. The average LIR is up to an order of magnitude higher than for SMGs at lower redshifts. Our SMGs follow the correlation between dust temperature and IR luminosity as derived for Herschel-selected 0.1 <z< 2 galaxies. We study the IR-radio correlation for our sources and find a deviation from that derived for z< 3 ULIRGs (⟨ qIR ⟩ = 1.95 ± 0.26 for our sample, compared to q ≈ 2.6 for IR luminous galaxies at z< 2). In summary, we find that the physical properties derived for our z> 4 SMGs put them at the high end of the LIR–Tdust distribution of SMGs, and that our SMGs form a morphologically heterogeneous sample. Thus, additional in-depth analyses of large, statistical samples of high-redshift SMGs are needed to fully understand their role in galaxy formation and evolution.
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