ABSTRACT In this paper we use ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field in band 3 and band 6, to place blind constraints on the CO luminosity function and the evolution of ...the cosmic molecular gas density as a function of redshift up to z ∼ 4.5. This study is based on galaxies that have been selected solely through their CO emission and not through any other property. In all of the redshift bins the ASPECS measurements reach the predicted "knee" of the CO luminosity function (around 5 × 109 K km s−1 pc2). We find clear evidence of an evolution in the CO luminosity function with respect to z ∼ 0, with more CO-luminous galaxies present at z ∼ 2. The observed galaxies at z ∼ 2 also appear more gas-rich than predicted by recent semi-analytical models. The comoving cosmic molecular gas density within galaxies as a function of redshift shows a drop by a factor of 3-10 from z ∼ 2 to z ∼ 0 (with significant error bars), and possibly a decline at z > 3. This trend is similar to the observed evolution of the cosmic star formation rate density. The latter therefore appears to be at least partly driven by the increased availability of molecular gas reservoirs at the peak of cosmic star formation (z ∼ 2).
We discuss the nature and physical properties of gas-mass selected galaxies in the ALMA spectroscopic survey (ASPECS) of the Hubble Ultra Deep Field (HUDF). We capitalize on the deep optical ...integral-field spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE) HUDF Survey and multiwavelength data to uniquely associate all 16 line emitters, detected in the ALMA data without preselection, with rotational transitions of carbon monoxide (CO). We identify 10 as CO(2-1) at 1 < z < 2, 5 as CO(3-2) at 2 < z < 3, and 1 as CO(4-3) at z = 3.6. Using the MUSE data as a prior, we identify two additional CO(2-1) emitters, increasing the total sample size to 18. We infer metallicities consistent with (super-)solar for the CO-detected galaxies at z ≤ 1.5, motivating our choice of a Galactic conversion factor between CO luminosity and molecular gas mass for these galaxies. Using deep Chandra imaging of the HUDF, we determine an X-ray AGN fraction of 20% and 60% among the CO emitters at z ∼ 1.4 and z ∼ 2.6, respectively. Being a CO-flux-limited survey, ASPECS-LP detects molecular gas in galaxies on, above, and below the main sequence (MS) at z ∼ 1.4. For stellar masses ≥1010 (1010.5) , we detect about 40% (50%) of all galaxies in the HUDF at 1 < z < 2 (2 < z < 3). The combination of ALMA and MUSE integral-field spectroscopy thus enables an unprecedented view of MS galaxies during the peak of galaxy formation.
We present a study of six far-infrared fine structure lines in the z = 4.225 lensed dusty star-forming galaxy SPT 0418−47 to probe the physical conditions of its interstellar medium (ISM). In ...particular, we report Atacama Pathfinder EXperiment (APEX) detections of the OI 145 μm and OIII 88 μm lines and Atacama Compact Array (ACA) detections of the NII 122 and 205 μm lines. The OI 145 μm/CII 158 μm line ratio is ∼5× higher compared to the average of local galaxies. We interpret this as evidence that the ISM is dominated by photo-dissociation regions with high gas densities. The line ratios, and in particular those of OIII 88 μm and NII 122 μm imply that the ISM in SPT 0418−47 is already chemically enriched to nearly solar metallicity. While the strong gravitational amplification was required to detect these lines with APEX, larger samples can be observed with the Atacama Large Millimeter/submillimeter Array (ALMA), and should allow observers to determine if the dense, solar metallicity ISM is common among these highly star-forming galaxies.
ABSTRACT We study the molecular gas properties of high-z galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets an ∼1 arcmin2 region in the Hubble Ultra Deep Field (UDF), a blind ...survey of CO emission (tracing molecular gas) in the 3 and 1 mm bands. Of a total of 1302 galaxies in the field, 56 have spectroscopic redshifts and correspondingly well-defined physical properties. Among these, 11 have infrared luminosities , i.e., a detection in CO emission was expected. Out of these, 7 are detected at various significance in CO, and 4 are undetected in CO emission. In the CO-detected sources, we find CO excitation conditions that are lower than those typically found in starburst/sub-mm galaxy/QSO environments. We use the CO luminosities (including limits for non-detections) to derive molecular gas masses. We discuss our findings in the context of previous molecular gas observations at high redshift (star formation law, gas depletion times, gas fractions): the CO-detected galaxies in the UDF tend to reside on the low- envelope of the scatter in the relation, but exceptions exist. For the CO-detected sources, we find an average depletion time of ∼1 Gyr, with significant scatter. The average molecular-to-stellar mass ratio ( /M*) is consistent with earlier measurements of main-sequence galaxies at these redshifts, and again shows large variations among sources. In some cases, we also measure dust continuum emission. On average, the dust-based estimates of the molecular gas are a factor ∼2-5× smaller than those based on CO. When we account for detections as well as non-detections, we find large diversity in the molecular gas properties of the high-redshift galaxies covered by ASPECS.
Abstract
We present measurements of the CO luminosity functions (LFs) and the evolution of the cosmic molecular gas density out to
z
∼ 6 based on an 8.5 arcmin
2
spectral scan survey at 3 mm of the ...iconic Hubble Deep Field North (HDF-N) observed with the NOrthern Extended Millimeter Array (NOEMA). We use matched filtering to search for line emission from galaxies and determine their redshift probability distributions exploiting the extensive multiwavelength data for the HDF-N. We identify the seven highest-fidelity sources as CO emitters at 1 <
z
< 6, including the well-known submillimeter galaxy HDF 850.1 at
z
= 5.18. Four high-fidelity 3 mm continuum sources are found to be radio galaxies at
z
≤ 1, plus HDF 850.1. We constrain the CO LFs in the HDF-N out to
z
∼ 6, including a first measurement of the CO(5–4) LF at 〈
z
〉 = 5.0. The relatively large area and depth of the NOEMA HDF-N survey extends the existing LFs at 1 <
z
< 4 above the knee, yielding a somewhat lower density by 0.15–0.4 dex at the overlap region for the CO(2–1) and CO(3–2) transitions, attributed to cosmic variance. We perform a joint analysis of the CO LFs in the HDF-N and Hubble Ultra Deep Field from ASPECS, finding that they can be well described by a single Schechter function. The evolution of the cosmic molecular gas density from a joint analysis is in good agreement with earlier determinations. This implies that the impact of cosmic field-to-field variance on the measurements is consistent with previous estimates, adding to the challenges for simulations that model galaxies from first principles.
Aims. We present and study spatially resolved imaging obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) of multiple 12CO(J = 6 − 5, 8−7, and 9−8) and two H2O(202−111 and 211−202) ...emission lines and cold dust continuum toward the gravitationally lensed dusty star-forming galaxy SPT 0346-52 at z = 5.656. Methods. Using a visibility-domain source-plane reconstruction we probe the structure and dynamics of the different components of the interstellar medium (ISM) in this galaxy down to scales of 1 kpc in the source plane. Results. Measurements of the intrinsic sizes of the different CO emission lines indicate that the higher J transitions trace more compact regions in the galaxy. Similarly, we find smaller dust continuum intrinsic sizes with decreasing wavelength, based on observations at rest frame 130, 300, and 450 μm. The source shows significant velocity structure, and clear asymmetry where an elongated structure is observed in the source plane with significant variations in their reconstructed sizes. This could be attributed to a compact merger or turbulent disk rotation. The differences in velocity structure through the different line tracers, however, hint at the former scenario in agreement with previous CII line imaging results. Measurements of the CO line ratios and magnifications yield significant variations as a function of velocity, suggesting that modeling of the ISM using integrated values could be misinterpreted. Modeling of the ISM in SPT 0346-52 based on delensed fluxes indicates a highly dense and warm medium, qualitatively similar to that observed in high-redshift quasar hosts.
We present a new semiempirical model for the dust continuum number counts of galaxies at 1.1 mm and 850 m. Our approach couples an observationally motivated model for the stellar mass and star ...formation rate distribution of galaxies with empirical scaling relations to predict the dust continuum flux density of these galaxies. Without a need to tweak the IMF, the model reproduces the currently available observations of the 1.1 mm and 850 m number counts, including the observed flattening in the 1.1 mm number counts below 0.3 mJy and the number counts in discrete bins of different galaxy properties. Predictions of our work include the following: (1) the galaxies that dominate the number counts at flux densities below 1 mJy (3 mJy) at 1.1 mm (850 m) have redshifts between z = 1 and z = 2, stellar masses of ∼5 × 1010 M , and dust masses of ∼108 M ; (2) the flattening in the observed 1.1 mm number counts corresponds to the knee of the 1.1 mm luminosity function. A similar flattening is predicted for the number counts at 850 m; (3) the model reproduces the redshift distribution of current 1.1 mm detections; and (4) to efficiently detect large numbers of galaxies through their dust continuum, future surveys should scan large areas once reaching a 1.1 mm flux density of 0.1 mJy rather than integrating to fainter fluxes. Our modeling framework also suggests that the amount of information on galaxy physics that can be extracted from the 1.1 mm and 850 m number counts is almost exhausted.
SPT0346-52 is one of the most most luminous and intensely star-forming galaxies in the universe, with and . In this paper, we present ALMA observations of the 158 m emission line in this z = 5.7 ...dusty star-forming galaxy. We use a pixellated lensing reconstruction code to spatially and kinematically resolve the source-plane and rest-frame 158 m dust continuum structure at ∼700 pc (∼0 12) resolution. We discuss the deficit with a pixellated study of the LC ii/LFIR ratio in the source plane. We find that individual pixels within the galaxy follow the same trend found using unresolved observations of other galaxies, indicating that the deficit arises on scales 700 pc. The lensing reconstruction reveals two spatially and kinematically separated components (∼1 kpc and ∼500 km s−1 apart) connected by a bridge of gas. Both components are found to be globally unstable, with Toomre Q instability parameters everywhere. We argue that SPT0346-52 is undergoing a major merger, which is likely driving the intense and compact star formation.
Abstract
SPT0311-58 is the most massive infrared luminous system discovered so far during the Epoch of Reionization (EoR). In this paper, we present a detailed analysis of the molecular interstellar ...medium at
z
= 6.9, through high resolution observations of the CO(6–5), CO(7–6), CO(10–9), C
i
(2–1), and p‐H
2
O(2
1,1
−2
0,2
) lines and dust continuum emissions with the Atacama Large Millimeter/submillimeter Array. The system consists of a pair of intensely star-forming, gravitationally lensed galaxies (labeled West and East). The intrinsic far-infrared luminosity is (16 ± 4) × 10
12
L
⊙
in West and (27 ± 4) × 10
11
L
⊙
in East. We model the dust, CO, and C
i
using non-local thermodynamic equilibrium radiative transfer models and estimate the intrinsic gas mass to be (5.4 ± 3.4) × 10
11
M
⊙
in West and (3.1 ± 2.7) × 10
10
M
⊙
in East. We find that the CO spectral line energy distribution in West and East are typical of high-redshift submillimeter galaxies (SMGs). The CO-to-H
2
conversion factor (
α
CO
) and the gas depletion timescales estimated from the model are consistent with the high-redshift SMGs in the literature within the uncertainties. We find no evidence of evolution of depletion time with redshift in SMGs at
z
> 3. This is the most detailed study of molecular gas content of a galaxy in the EoR to date, with the most distant detection of H
2
O in a galaxy without any evidence for active galactic nuclei in the literature.
Anthropogenic land use change is a major driver of zoonotic pathogen spillover from wildlife to humans. According to the land use‐induced spillover model, land use change alters environmental ...conditions that in turn alter the dynamics between zoonotic pathogens and their wildlife hosts. Thus, in response to the global spread of the SARS‐CoV‐2 virus (the agent of COVID‐19 disease), there have been renewed calls for landscape conservation as a disease preventive measure, including by the G7 Ministers responsible for Climate and the Environment. Landscape immunity, as a new construct, points to four paradigm shifts the world must favor to effectively mitigate pandemic risks. We provide a landscape immunity primer for policy makers and make the case for “world views” that place Homo sapiens within ecological systems, regard human health as an ecological service, prioritize investments in prevention, and apply ecological restoration to human health goals. Crisis is a conversation starter for reimagining and recommitting ourselves to what is most vital and generative. We urge world leaders to make the move to a nature‐positive world.
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![Spatially Resolved [C ii] E...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-637X_2041-8205_1538-4357/small "Spatially Resolved [C ii] Emission in SPT0346-52: A Hyper-starburst Galaxy Merger at z ∼ 5.7")
