48 research outputs found
ALMA reveals the molecular gas properties of five star-forming galaxies across the main sequence at 3
International audienceWe present the detection of CO(5-4) with S/N> 7 - 13 and a lower CO transition with S/N > 3 (CO(4-3) for 4 galaxies, and CO(3-2) for one) with ALMA in band 3 and 4 in five main sequence star-forming galaxies with stellar masses 3-6x10^10 M/M_sun at 3 < z < 3.5. We find a good correlation between the total far-infrared luminosity LFIR and the luminosity of the CO(5-4) transition L'CO(5-4), where L'CO(5-4) increases with SFR, indicating that CO(5-4) is a good tracer of the obscured SFR in these galaxies. The two galaxies that lie closer to the star-forming main sequence have CO SLED slopes that are comparable to other star-forming populations, such as local SMGs and BzK star-forming galaxies; the three objects with higher specific star formation rates (sSFR) have far steeper CO SLEDs, which possibly indicates a more concentrated episode of star formation. By exploiting the CO SLED slopes to extrapolate the luminosity of the CO(1-0) transition, and using a classical conversion factor for main sequence galaxies of alpha_CO = 3.8 M_sun(K km s^-1 pc^-2)^-1, we find that these galaxies are very gas rich, with molecular gas fractions between 60 and 80%, and quite long depletion times, between 0.2 and 1 Gyr. Finally, we obtain dynamical masses that are comparable with the sum of stellar and gas mass (at least for four out of five galaxies), allowing us to put a first constraint on the alpha_CO parameter for main sequence galaxies at an unprecedented redshift
A multiwavelength study of a massive, active galaxy at z similar to 2:coupling the kinematics of the ionized and molecular gas
We report a multiwavelength study of the massive ( M-* greater than or similar to 10(11)M(circle dot)), z similar to 2 star-forming galaxy GMASS 0953, which hosts an obscured AGN. We combined near-infrared observations of the GNIRS, SINFONI and KMOS spectrographs to study the kinematics of the [O III] lambda 5007 and H alpha emission lines. Our analysis shows that GMASS 0953 may host an ionized disc extending up to 13 kpc, which rotates at a velocity of V-ion = 203(-20)(+17) km s(-1) at the outermost radius. Evidence of rotation on a smaller scale (R similar to 1 kpc) arises from the CO(J = 6-5) line. The central velocity V-CO = 320(-53)(+92) km s(-1) traced by the molecular gas is higher than V-ion, suggesting that the galaxy harbours a multiphase disc with a rotation curve that peaks in the very central regions. The galaxy appears well located on the z = 0 baryonic Tully-Fisher relation. We also discuss the possibility that the [O III] lambda 5007 and H alpha velocity gradients are due to a galactic-scale wind. Besides, we found evidence of an AGN-driven outflow traced by a broad blueshifted wing affecting the [O III] lambda 5007 line, which presents a velocity offset Delta v = -535 +/- 152 km s(-1) from the systemic velocity. Because of the short depletion time-scale (tau(dep) similar to 10(8) yr) due to gas ejection and gas consumption by star formation activity, GMASS 0953 may likely evolve into a passive galaxy. However, the role of the AGN in depleting the gas reservoir of the galaxy is quite unclear because of the uncertainties affecting the outflow rate
Illuminating the Dark Side of Cosmic Star Formation II. A second date with RS-NIRdark galaxies in COSMOS
About 12 billion years ago, the Universe was first experiencing light again
after the dark ages, and galaxies filled the environment with stars, metals and
dust. How efficient was this process? How fast did these primordial galaxies
form stars and dust? We can answer these questions by tracing the Star
Formation Rate Density (SFRD) back to its widely unknown high redshift tail,
traditionally observed in the Near-InfraRed (NIR), Optical and UV bands. Thus,
the objects with a high amount of dust were missing. We aim to fill this
knowledge gap by studying Radio Selected NIR-dark (\textit{RS-NIRdark})
sources, i.e. sources not having a counterpart at UV-to-NIR wavelengths. We
widen the sample by Talia et al. (2021) from 197 to 272 objects in the COSMic
evolution Survey (COSMOS) field, including also photometrically contaminated
sources, previously excluded. Another important step forward consists in the
visual inspection of each source in the bands from u* to MIPS-24m.
According to their "environment" in the different bands, we are able to
highlight different cases of study and calibrate an appropriate photometric
procedure for the objects affected by confusion issues. We estimate that the
contribution of RS-NIRdark to the Cosmic SFRD at 3z5 is 10--25
of that based on UV-selected galaxies
ALMA Reveals the Molecular Gas Properties of Five Star-forming Galaxies across the Main Sequence at 3
We present the detection of CO (5â4) with signal-to-noise ratio (S/N) > 7-13 and a lower CO transition with S/N > 3 (CO (4â3) for four galaxies, and CO (3â2) for one) with the Atacama Large Millimeter/submillimeter Array in bands 3 and 4 in five main-sequence (MS) star-forming galaxies with stellar masses (3-6) x 1010 M â at 3 < z < 3.5. We find a good correlation between the total far-infrared luminosity L FIR and the luminosity of the CO (5â4) transition , where increases with star formation rate (SFR), indicating that CO (5â4) is a good tracer of the obscured SFR in these galaxies. The two galaxies that lie closer to the star-forming MS have CO spectral line energy distribution (SLED) slopes that are comparable to other star-forming populations, such as local submillimeter galaxies and BzK star-forming galaxies; the three objects with higher specific star formation rates have far steeper CO SLEDs, which possibly indicates a more concentrated episode of star formation. By exploiting the CO SLED slopes to extrapolate the luminosity of the CO (1â0) transition and using a classical conversion factor for MS galaxies of , we find that these galaxies are very gas-rich, with molecular gas fractions between 60% and 80% and quite long depletion times, between 0.2 and 1 Gyr. Finally, we obtain dynamical masses that are comparable to the sum of stellar and gas mass (at least for four out of five galaxies), allowing us to put a first constraint on the α CO parameter for MS galaxies at an unprecedented redshift.This work is based on ALMA data from the project ADS/JAO.
ALMA#2015.1.01590.S. ALMA is a partnership of ESO
(representing its member states), NSF (USA), and NINS (Japan),
together with NRC (Canada), NSC 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. We are grateful for the support from the
Italian regional ALMA ARC. P.C. and L.M. acknowledge support
from the BIRD 2018 research grant from the UniversitĂ degli
Studi di Padova; P.C. acknowledges support from the CONICYT/FONDECYT program No. 1150216; E.I. acknowledges
partial support from FONDECYT through grant No. 1171710;
D.L. and E.S. acknowledge funding from the European Research
Council (ERC) under the European Unionâs Horizon 2020
research and innovation programme (grant agreement No.
694343)
The stellar metallicities of massive quiescent galaxies at 1.0 < z < 1.3 from KMOS+VANDELS
We present a rest-frame UV-optical stacked spectrum representative of massive
quiescent galaxies at . The stack
is constructed using VANDELS survey data, combined with new KMOS observations.
We apply two independent full-spectral-fitting approaches, measuring a total
metallicity, [Z/H]= with Bagpipes, and [Z/H]= with
Alf, a fall of dex compared with the local Universe. We also
measure an iron abundance, [Fe/H] =, a fall of dex
compared with the the local Universe. We measure the alpha enhancement via the
magnesium abundance, obtaining [Mg/Fe]=0.12, consistent with
similar-mass galaxies in the local Universe, indicating no evolution in the
average alpha enhancement of log quiescent galaxies over
the last Gyr. This suggests the very high alpha enhancements recently
reported for several bright quiescent galaxies are due to their
extreme masses, log, rather than being typical
of the population. The metallicity evolution we observe with
redshift (falling [Z/H], [Fe/H], constant [Mg/Fe]) is consistent with recent
studies. We recover a mean stellar age of Gyr,
corresponding to a formation redshift, z_\rm{form}=2.4^{+0.6}_{-0.3}. Recent
studies have obtained varying average formation redshifts for
massive quiescent galaxies, and, as these studies report consistent
metallicities, we identify different star-formation-history models as the most
likely cause. Larger spectroscopic samples from upcoming ground-based
instruments will provide precise constraints on ages and metallicities at
. Combining these with precise JWST quiescent-galaxy
stellar-mass functions will provide an independent test of formation redshifts
derived from spectral fitting.Comment: 16 pages, 3 figures, accepted for publication in Ap
High-velocity outflows in massive post-starburst galaxies at z > 1
We investigate the prevalence of galactic-scale outflows in post-starburst (PSB) galaxies at high redshift (1 1010Mââ ) PSBs at z > 1, there is clear evidence for a strong blue-shifted component to the Mgâii absorption feature, indicative of high-velocity outflows (â voutâŒ1150±160kmsâ1â ) in the interstellar medium. We conclude that such outflows are typical in massive PSBs at this epoch, and potentially represent the residual signature of a feedback process that quenched these galaxies. Using full spectral fitting, we also obtain a typical stellar velocity dispersion Ï* for these PSBs of âŒ200kmsâ1â , which confirms they are intrinsically massive in nature (dynamical mass MdâŒ1011Mââ ). Given that these high-z PSBs are also exceptionally compact (re ⌠1â2kpcâ ) and spheroidal (SĂ©rsic index n ⌠3), we propose that the outflowing winds may have been launched during a recent compaction event (e.g. major merger or disc collapse) that triggered either a centralized starburst or active galactic nuclei (AGN) activity. Finally, we find no evidence for AGN signatures in the optical spectra of these PSBs, suggesting they were either quenched by stellar feedback from the starburst itself, or that if AGN feedback is responsible, the AGN episode that triggered quenching does not linger into the post-starburst phase.Publisher PDFPeer reviewe
ElentaÌri: a massive proto-supercluster at z ⌠3.3 in the COSMOS field
Motivated by spectroscopic confirmation of three overdense regions in the COSMOS field at z similar to 3.35, we analyse the uniquely deep multiwavelength photometry and extensive spectroscopy available in the field to identify any further related structure. We construct a three-dimensional density map using the Voronoi tesselation Monte Carlo method and find additional regions of significant overdensity. Here, we present and examine a set of six overdense structures at 3.20 < z < 3.45 in the COSMOS field, the most well-characterized of which, PCl J0959 + 0235, has 80 spectroscopically confirmed members and an estimated mass of 1.35 x 10(15) M-circle dot, and is modelled to virialize at z similar to 1.5-2.0. These structures contain 10 overdense peaks with >5 sigma overdensity separated by up to 70 cMpc, suggestive of a proto-supercluster similar to the Hyperion system at z similar to 2.45. Upcoming photometric surveys with JWST such as COSMOS-Web, and further spectroscopic follow-up will enable more extensive analysis of the evolutionary effects that such an environment may have on its component galaxies at these early times
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
Unveiling the distant Universe: Characterizing Galaxies in the first epoch of COSMOS-Web
We report the identification of 15 galaxy candidates at using the
initial COSMOS-Web JWST observations over 77 arcmin through four NIRCam
filters (F115W, F150W, F277W, F444W) with an overlap with MIRI (F770W) of 8.7
arcmin. We fit the sample using several publicly-available SED fitting and
photometric redshift codes and determine their redshifts between and
(), UV-magnitudes between M =
21.2 and 19.5 (with M) and rest-frame
UV slopes (). These galaxies are, on average, more
luminous than most candidates discovered by JWST so far in the
literature, while exhibiting similar blue colors in their rest-frame UV. The
rest-frame UV slopes derived from SED-fitting are blue ([2.0,
2.7]) without reaching extremely blue values as reported in other recent
studies at these redshifts. The blue color is consistent with models that
suggest the underlying stellar population is not yet fully enriched in metals
like similarly luminous galaxies in the lower redshift Universe. The derived
stellar masses with MM are not in tension with the standard
CDM model and our measurement of the volume density of such UV
luminous galaxies aligns well with previously measured values presented in the
literature at . Our sample of galaxies, although compact, are
significantly resolved.Comment: Submitted to Ap