86 research outputs found
The ALMA-ALPAKA survey I: high-resolution CO and [CI] kinematics of star-forming galaxies at z = 0.5-3.5
Spatially-resolved studies of the kinematics of galaxies provide crucial
insights into their assembly and evolution, enabling to infer the properties of
the dark matter halos, derive the impact of feedback on the ISM, characterize
the outflow motions. To date, most of the kinematic studies at z=0.5-3.5 were
obtained using emission lines tracing the warm, ionized gas. However, whether
these provide an exhaustive or only a partial view of the dynamics of galaxies
and of the properties of the ISM is still debated. Complementary insights on
the cold gas kinematics are therefore needed. We present ALPAKA, a project
aimed at gathering high-resolution observations of CO and [CI] emission lines
of star-forming galaxies at z=0.5-3.5 from the ALMA public archive. With 147
hours of total integration time, ALPAKA assembles ~0.25'' observations for 28
star-forming galaxies, the largest sample with spatially-resolved cold gas
kinematics as traced by either CO or [CI] at z>0.5. By combining
multi-wavelength ancillary data, we derive the stellar masses () and
star-formation rates (SFR) for our targets, finding values of M and SFR of 10-3000 M/yr. A large fraction of
ALPAKA galaxies (19/28) lie in overdense regions (clusters, groups, and
protoclusters). We exploit the ALMA data to infer their dynamical state and we
find that 19/28 ALPAKA galaxies are rotating disks, 2 are interacting systems,
while for the remaining 7 sources the classification is uncertain. The disks
have velocity dispersion values that are typically larger in the innermost
regions than in the outskirts, with a median value for the entire disk sample
of 35 km/s. Despite the bias of our sample towards galaxies
hosting very energetic mechanisms, the ALPAKA disks have high ratios of
ordered-to-random motion () with a median value of 9.Comment: 35 pages, 23 figures, 5 tables; submitted to A&A. The data and the
outputs of the kinematic analysis will be made available at
https://alpaka-survey.github.io/index.html once the paper is accepted.
Comments are welcom
Mapping Obscuration to Reionization with ALMA (MORA): 2 mm Efficiently Selects the Highest-redshift Obscured Galaxies
We present the characteristics of 2 mm selected sources from the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous survey conducted to date, the Mapping Obscuration to Reionization with ALMA (MORA) survey covering 184 arcmin2 at 2 mm. Twelve of 13 detections above 5σ are attributed to emission from galaxies, 11 of which are dominated by cold dust emission. These sources have a median redshift of primarily based on optical/near-infrared photometric redshifts with some spectroscopic redshifts, with 77% ± 11% of sources at z > 3 and 38% ± 12% of sources at z > 4. This implies that 2 mm selection is an efficient method for identifying the highest-redshift dusty star-forming galaxies (DSFGs). Lower-redshift DSFGs (z < 3) are far more numerous than those at z > 3 yet are likely to drop out at 2 mm. MORA shows that DSFGs with star formation rates in excess of 300 M ⊙ yr−1 and a relative rarity of ∼10−5 Mpc−3 contribute ∼30% to the integrated star formation rate density at 3 < z < 6. The volume density of 2 mm selected DSFGs is consistent with predictions from some cosmological simulations and is similar to the volume density of their hypothesized descendants: massive, quiescent galaxies at z > 2. Analysis of MORA sources’ spectral energy distributions hint at steeper empirically measured dust emissivity indices than reported in typical literature studies, with . The MORA survey represents an important step in taking census of obscured star formation in the universe’s first few billion years, but larger area 2 mm surveys are needed to more fully characterize this rare population and push to the detection of the universe’s first dusty galaxies
COSMOS2020: The Galaxy Stellar Mass Function: the assembly and star formation cessation of galaxies at
How galaxies form, assemble, and cease their star-formation is a central
question within the modern landscape of galaxy evolution studies. These
processes are indelibly imprinted on the galaxy stellar mass function (SMF). We
present constraints on the shape and evolution of the SMF, the quiescent galaxy
fraction, and the cosmic stellar mass density across 90% of the history of the
Universe from via the COSMOS survey. Now with deeper and
more homogeneous near-infrared coverage exploited by the COSMOS2020 catalog, we
leverage the large 1.27 deg effective area to improve sample statistics
and understand cosmic variance particularly for rare, massive galaxies and push
to higher redshifts with greater confidence and mass completeness than previous
studies. We divide the total stellar mass function into star-forming and
quiescent sub-samples through color-color selection. Measurements are
then fitted with Schechter functions to infer the intrinsic SMF, the evolution
of its key parameters, and the cosmic stellar mass density out to . We
find a smooth, monotonic evolution in the galaxy SMF since , in
agreement with previous studies. The number density of star-forming systems
seems to have undergone remarkably consistent growth spanning four decades in
stellar mass from whereupon high-mass systems become
predominantly quiescent (i.e. downsizing). An excess of massive systems at
with strikingly red colors, some newly identified, increase the
observed number densities to the point where the SMF cannot be reconciled with
a Schechter function. Systematics including cosmic variance and/or AGN
contamination are unlikely to fully explain this excess, and so we speculate
that there may be contributions from dust-obscured objects similar to those
found in FIR surveys. (abridged)Comment: 39 pages, 24 figures, accepted for publication in A&A. Data files
containing key measurements are available for download:
https://doi.org/10.5281/zenodo.780883
JWST and ALMA discern the assembly of structural and obscured components in a high-redshift starburst galaxy
We present observations and analysis of the starburst, PACS-819, at z=1.45
( M), using high-resolution (;
0.8 kpc) ALMA and multi-wavelength JWST images from the COSMOS-Web program.
Dissimilar to HST/ACS images in the rest-frame UV, the redder NIRCam and MIRI
images reveal a smooth central mass concentration and spiral-like features,
atypical for such an intense starburst. Through dynamical modeling of the CO
J=5--4 emission with ALMA, PACS-819 is rotation-dominated thus has a disk-like
nature. However, kinematic anomalies in CO and asymmetric features in the bluer
JWST bands (e.g., F150W) support a more disturbed nature likely due to
interactions. The JWST imaging further enables us to map the distribution of
stellar mass and dust attenuation, thus clarifying the relationships between
different structural components, not discernable in the previous HST images.
The CO J = 5 -- 4 and FIR dust continuum emission are co-spatial with a
heavily-obscured starbursting core (<1 kpc) which is partially surrounded by
much less obscured star-forming structures including a prominent arc, possibly
a tidally-distorted dwarf galaxy, and a clump, either a sign of an ongoing
violent disk instability or a recently accreted low-mass satellite. With
spatially-resolved maps, we find a high molecular gas fraction in the central
area reaching (/) and short depletion times
( 120 Myrs) across the entire system. These
observations provide insights into the complex nature of starbursts in the
distant universe and underscore the wealth of complementary information from
high-resolution observations with both ALMA and JWST.Comment: 18 pages, 12 figures, Submitted to Ap
The Gas and Stellar Content of a Metal-poor Galaxy at z = 8.496 as Revealed by JWST and ALMA
We present a joint analysis of the galaxy S04590 at z = 8.496 based on NIRSpec, NIRCam, and NIRISS observations obtained as part of the Early Release Observations program of the James Webb Space Telescope (JWST) and the far-infrared [C ii] 158 μm emission line detected by dedicated Atacama Large Millimeter/submillimeter Array (ALMA) observations. We determine the physical properties of S04590 from modeling of the spectral energy distribution (SED) and through the redshifted optical nebular emission lines detected with JWST/NIRSpec. The best-fit SED model reveals a low-mass (M ⋆ = 107.2-108 M ⊙) galaxy with a low oxygen abundance of 12 + log ( O / H ) = 7.16 − 0.12 + 0.10 derived from the strong nebular and auroral emission lines. Assuming that [C ii] effectively traces the interstellar medium, we estimate the total gas mass of the galaxy to be M gas = (8.0 \ub1 4.0)
7 108 M ⊙ based on the luminosity and spatial extent of [C ii]. This yields an exceptionally high gas fraction, f gas = M gas/(M gas + M ⋆) ≳ 90%, though one still consistent with the range expected for low metallicity. We further derive the metal mass of the galaxy based on the gas mass and gas-phase metallicity, which we find to be consistent with the expected metal production from Type II supernovae. Finally, we make the first constraints on the dust-to-gas (DTG) and dust-to-metal (DTM) ratios of galaxies in the epoch of reionization at z ≳ 6, showing overall low mass ratios of logDTG < −3.8 and logDTM < −0.5, though they are consistent with established scaling relations and in particular with those of the local metal-poor galaxy I Zwicky 18. Our analysis highlights the synergy between ALMA and JWST in characterizing the gas, metal, and stellar content of the first generation of galaxies
The Web Epoch of Reionization Lyman- Survey (WERLS) I. MOSFIRE Spectroscopy of Lyman- Emitters
We present the first results from the Web Epoch of Reionization
Lyman- Survey (WERLS), a spectroscopic survey of Lyman-
emission using Keck I/MOSFIRE and LRIS. WERLS targets bright () galaxy
candidates with photometric redshifts of selected
from pre-JWST imaging embedded in the Epoch of Reionization (EoR) within three
JWST deep fields: CEERS, PRIMER, and COSMOS-Web. Here, we report 11
Lyman- emitters (LAEs; 3 secure and 8 tentative candidates) detected in
the first five nights of WERLS MOSFIRE data. We estimate our observed LAE yield
is %, broadly consistent with expectations assuming some loss from
redshift uncertainty, contamination from sky OH lines, and that the Universe is
approximately half-ionized at this epoch, whereby observable Lyman-
emission is unlikely for galaxies embedded in a neutral intergalactic medium.
Our targets are selected to be UV-bright, and span a range of absolute UV
magnitudes with . With two LAEs detected at
, we also consider the possibility of an ionized bubble at this
redshift. Future synergistic Keck+JWST efforts will provide a powerful tool for
pinpointing beacons of reionization and mapping the large scale distribution of
mass relative to the ionization state of the Universe.Comment: 27 pages, 8 figures; ApJ submitte
ALMA Lensing Cluster Survey: and Photometry of 33 Lensed Fields Built with CHArGE
We present a set of multi-wavelength mosaics and photometric catalogs in the
ALMA lensing cluster survey (ALCS) fields. The catalogs were built by
reprocessing of archival data from the CHArGE compilation, taken by the
() in the RELICS, CLASH and
Hubble Frontier Fields. Additionally we have reconstructed the
IRAC 3.6 and 4.5 m mosaics, by utilising all the
available archival IRSA/SHA exposures. To alleviate the effect of blending in
such a crowded region, we have modelled the photometry by
convolving the detection image with the PSF
using the novel software. The final catalogs contain 218,000
sources, covering a combined area of 690 arcmin. These catalogs will serve
as an important tool in aiding the search of the sub-mm galaxies in future ALMA
surveys, as well as follow ups of the dark - IRAC sources.
Coupled with the available photometry the addition of the 3.6
and 4.5 m bands will allow us to place a better constraint on photometric
redshifts and stellar masses of these objects, thus giving us an opportunity to
identify high-redshift candidates for spectroscopic follow ups and answer the
important questions regarding the epoch of reionization and formation of first
galaxies.Comment: 35 pages, 19 figures, 4 tables. Submitted to ApJS. Mosaics and
photometric catalogs can be accessed online
https://github.com/dawn-cph/alcs-cluster
Strong (Hb + [OIII]) and Ha emitters at redshift z ~ 7-8 unveiled with JWST/NIRCam and MIRI imaging in the Hubble eXtreme Deep Field (XDF)
The JWST is revolutionizing the study of high-redshift galaxies by providing
for the first time a high-sensitivity view of the early Universe at infrared
wavelengths, both with its Near Infrared Camera (NIRCam) and Mid Infrared
Instrument (MIRI). In this paper, we make use of medium and broad-band NIRCam
imaging, as well as ultra-deep MIRI 5.6 microns imaging, in the Hubble eXtreme
Deep Field (XDF) to identify prominent line emitters at z ~ 7-8. Out of a total
of 58 galaxies at z ~ 7-8, we find 18 robust candidates (~31%) for prominent
(Hb + [OIII]) emitters, based on their enhanced fluxes in the F430M and F444W
filters, with rest-frame EW(Hb + [OIII]) ~ 87 - 2100 A. Among these emitters,
16 lie on the MIRI coverage area and 12 show a clear flux excess at 5.6
microns, indicating the simultaneous presence of a prominent Ha emission line
with rest-frame EW(Ha) ~ 200 - 3000 A. This is the first time that Ha emission
can be detected in individual galaxies at z>7. The Ha line, when present,
allows us to separate the contributions of the Hb and [OIII] emission lines to
the (Hb + [OIII]) complex and derive Ha-based star formation rates (SFRs). We
find that in some cases [OIII]/Hb > 1, suggesting low metallicities, but a few
have [OIII]/Hb < 1, so the NIRCam flux excess is mainly driven by Hb. The vast
majority of prominent line emitters are very young starbursts or galaxies on
their way to/from the starburst cloud. They make for a cosmic SFR density
log10(SFRD_Ha / Msun yr^-1 Mpc^-3) ~ 2.35, which is about a third of the total
value at z ~ 7-8. Therefore, the strong Ha emitters likely had an important
role in reionization.Comment: 15 pages, 9 figures. Submitted to Ap
Recommended from our members
GOODS-ALMA 2.0: starbursts in the main sequence reveal compact star formation regulating galaxy evolution prequenching
Compact star formation appears to be generally common in dusty star-forming galaxies (SFGs). However, its role in the framework set by the scaling relations in galaxy evolution remains to be understood. In this work we follow up on the galaxy sample from the GOODS-ALMA 2.0 survey, an ALMA blind survey at 1.1 mm covering a continuous area of 72.42 arcmin2 using two array configurations. We derived physical properties, such as star formation rates, gas fractions, depletion timescales, and dust temperatures for the galaxy sample built from the survey. There exists a subset of galaxies that exhibit starburst-like short depletion timescales, but they are located within the scatter of the so-called main sequence of SFGs. These are dubbed starbursts in the main sequence and display the most compact star formation and they are characterized by the shortest depletion timescales, lowest gas fractions, and highest dust temperatures of the galaxy sample, compared to typical SFGs at the same stellar mass and redshift. They are also very massive, accounting for ∼60% of the most massive galaxies in the sample (log(M*/M⊙) > 11.0). We find trends between the areas of the ongoing star formation regions and the derived physical properties for the sample, unveiling the role of compact star formation as a physical driver of these properties. Starbursts in the main sequence appear to be the extreme cases of these trends. We discuss possible scenarios of galaxy evolution to explain the results drawn from our galaxy sample. Our findings suggest that the star formation rate is sustained in SFGs by gas and star formation compression, keeping them within the main sequence even when their gas fractions are low and they are presumably on the way to quiescence
- …