65 research outputs found
Massive molecular gas reservoir in a luminous submillimeter galaxy during cosmic noon
No full textWe present multiband observations of an extremely dusty star-forming lensed galaxy (HERS1) at z = 2.553. High-resolution maps of HST/WFC3, SMA, and ALMA show a partial Einstein ring with a radius of ∼3′′. The deeper HST observations also show the presence of a lensing arc feature associated with a second lens source, identified to be at the same redshift as the bright arc based on a detection of the [N ii] 205 μm emission line with ALMA. A detailed model of the lensing system is constructed using the high-resolution HST/WFC3 image, which allows us to study the source-plane properties and connect rest-frame optical emission with properties of the galaxy as seen in submillimeter and millimeter wavelengths. Corrected for lensing magnification, the spectral energy distribution fitting results yield an intrinsic star formation rate of about 1000 ± 260 M ⊙ yr-1, a stellar mass M∗=4.3-1.0+2.2×1011M⊙, and a dust temperature Td=35-1+2 K. The intrinsic CO emission line (J up = 3, 4, 5, 6, 7, 9) flux densities and CO spectral line energy distribution are derived based on the velocity-dependent magnification factors. We apply a radiative transfer model using the large velocity gradient method with two excitation components to study the gas properties. The low-excitation component has a gas density nH2=103.8±0.6 cm-3 and kinetic temperature Tk=18-5+7 K, and the high-excitation component has nH2=103.1±0.4 cm-3 and Tk=480-220+260 K. Additionally, HERS1 has a gas fraction of about 0.19 ± 0.14 and is expected to last 100 Myr. These properties offer a detailed view of a typical submillimeter galaxy during the peak epoch of star formation activity
Recommended from our members
Evidence for Gas-phase Metal Deficiency in Massive Protocluster Galaxies at z ∼2.2
No full textWe study the mass-metallicity relation for 19 members of a spectroscopically confirmed protocluster in the COSMOS field at z = 2.2 (CC2.2), and compare it with that of 24 similarly selected field galaxies at the same redshift. Both samples are Hα emitting sources, chosen from the HiZELS narrowband survey, with metallicities derived from the N2([NII]λ6584/Hα) line ratio. For the mass-matched samples of protocluster and field galaxies, we find that protocluster galaxies with 109.9 M o˙ ≤ M ∗ ≤ 1010.9 M o˙ are metal deficient by 0.10 0.04 dex (2.5σ significance) compared to their coeval field galaxies. This metal deficiency is absent for low-mass galaxies, M ∗ < 109.9 M o˙. Moreover, relying on both spectral energy distribution derived and Hα (corrected for dust extinction based on M∗) star formation rates (SFRs), we find no strong environmental dependence of the SFR-M ∗ relation; however, we are not able to rule out the existence of small dependence due to inherent uncertainties in both SFR estimators. The existence of 2.5σ significant metal deficiency for massive protocluster galaxies favors a model in which funneling of the primordial cold gas through filaments dilutes the metal content of protoclusters at high redshifts (z ⪆ 2). At these redshifts, gas reservoirs in filaments are dense enough to cool down rapidly and fall into the potential well of the protocluster to lower the gas-phase metallicity of galaxies. Moreover, part of this metal deficiency could be originated from galaxy interactions that are more prevalent in dense environments. © 2021. The American Astronomical Society. All rights reserved.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Investigating the Effect of Galaxy Interactions on Star Formation at 0.5 < z < 3.0
No full textObservations and simulations of interacting galaxies and mergers in the local universe have shown that interactions can significantly enhance the star formation rates (SFRs) and fueling of active galactic nuclei (AGN). However, at higher redshift, some simulations suggest that the level of star formation enhancement induced by interactions is lower due to the higher gas fractions and already increased SFRs in these galaxies. To test this, we measure the SFR enhancement in a total of 2351 (1327) massive (M * > 1010 Msun) major (1 < M 1/M 2 < 4) spectroscopic galaxy pairs at 0.5 < z < 3.0 with DeltaV < 5000 km s−1 (1000 km s−1) and projected separation <150 kpc selected from the extensive spectroscopic coverage in the COSMOS and CANDELS fields. We find that the highest level of SFR enhancement is a factor of 1.23 − 0.09 + 0.08 in the closest projected separation bin (<25 kpc) relative to a stellar mass-, redshift-, and environment-matched control sample of isolated galaxies. We find that the level of SFR enhancement is a factor of ∼1.5 higher at 0.5 < z < 1 than at 1 < z < 3 in the closest projected separation bin. Among a sample of visually identified mergers, we find an enhancement of a factor of 1.86 − 0.18 + 0.29 (∼3 sigma) for coalesced systems. For this visually identified sample, we see a clear trend of increased SFR enhancement with decreasing projected separation (2.40 − 0.37 + 0.62 versus 1.58 − 0.20 + 0.29 for 0.5 < z < 1.6 and 1.6 < z < 3.0, respectively). The SFR enhancements seen in our interactions and mergers are all lower than the level seen in local samples at the same separation, suggesting that the level of interaction-induced star formation evolves significantly over this time period
Investigating the Effect of Galaxy Interactions on the Enhancement of Active Galactic Nuclei at 0.5 < z < 3.0
No full textGalaxy interactions and mergers are thought to play an important role in the evolution of galaxies. Studies in the nearby universe show a higher fraction of active galactic nuclei (AGNs) in interacting and merging galaxies than in their isolated counterparts, indicating that such interactions are important contributors to black hole growth. To investigate the evolution of this role at higher redshifts, we have compiled the largest known sample of major spectroscopic galaxy pairs (2381 with DeltaV < 5000 km s-1) at 0.5 < z < 3.0 from observations in the COSMOS and CANDELS surveys. We identify X-ray and IR AGNs among this kinematic pair sample, a visually identified sample of mergers and interactions, and a mass-, redshift-, and environment-matched control sample for each in order to calculate AGN fractions and the level of AGN enhancement as a function of relative velocity, redshift, and X-ray luminosity. While we see a slight increase in AGN fraction with decreasing projected separation, overall, we find no significant enhancement relative to the control sample at any separation. In the closest projected separation bin (< 25 kpc, DeltaV < 1000 km s-1), we find enhancements of a factor of for X-ray and IR-selected AGNs, respectively. While we conclude that galaxy interactions do not significantly enhance AGN activity on average over 0.5 < z < 3.0 at these separations, given the errors and the small sample size at the closest projected separations, our results would be consistent with the presence of low-level AGN enhancement
Accelerated Emergence of Evolved Galaxies in Early Overdensities at z ∼ 5.7
No full textWe report the identification of two galaxy overdensities at z ∼ 5.7 in the sightline of the galaxy cluster A2744. These overdensities consist of 25 and 17 member galaxies, spectroscopically confirmed with JWST NIRSpec micro-shutter assembly and NIRCam/WFSS. Each overdensity has a total stellar mass of ∼2 × 1010 M⊙ and a star formation rate of ∼200 M⊙ yr−1 within a central region of radius R = 2 Mpc (physical). The sensitive PRISM spectra allow us to identify six galaxies that show weak Hα + [N ii] emissions within the overdensities (25% ± 7%), whereas the fraction of such galaxies is found significantly lower (6% ± 2%) in field samples of the equivalent redshift range. These weak emission line galaxies, dubbed as wELGs, exhibit a strong continuum break at the 4000 Å rest frame, a characteristic feature of evolved stellar populations. The high observed fraction of wELGs in the two overdensities is consistent with the idea that high-density environments are an ideal site where galaxies can accelerate their evolutionary pace compared to field analogs. Our study pinpoints an early onset of environmental effects, already important within one billion years after the Big Bang, and provides a complementary perspective on the emergence of quenched, massive galaxies at lower redshifts. Potential contributions from black hole accretion feedback to the reduction in star formation activity are discussed, but the connection to the local environments remains unclear
Gas Phase Metallicities of Local Ultra-Luminous Infrared Galaxies Follow Normal Star-Forming Galaxies
No full textDespite advances in observational data, theoretical models, and computational
techniques to simulate key physical processes in the formation and evolution of
galaxies, the stellar mass assembly of galaxies still remains an unsolved
problem today. Optical spectroscopic measurements appear to show that the
gas-phase metallicities of local ultra-luminous infrared galaxies (ULIRGs) are
significantly lower than those of normal star-forming galaxies. This difference
has resulted in the claim that ULIRGs are fueled by metal-poor gas accretion
from the outskirts\cite{Mannucci10}. Here we report on a new set of gas-phase
metallicity measurements making use of the far-infrared spectral lines of
[O{\sc iii}]52 m, [O{\sc iii}]88 m, and [N{\sc iii}]57 m instead
of the usual optical lines. Photoionization models have resulted in a
metallicity diagnostic based on these three lines that break the electron
density degeneracy and reduce the scatter of the correlation significantly.
Using new data from SOFIA and archival data from Herschel Space Observatory, we
find that local ULIRGs lie on the mass-metallicity relation of star-forming
galaxies and have metallicities comparable to other galaxies with similar
stellar masses and star formation rates. The lack of a departure suggests that
ULIRGs follow the same mass assembly mechanism as luminous star-forming
galaxies and dex under-abundance in metallicities derived from
optical lines is a result of heavily obscured metal-rich gas which has a
negligible effect when using the FIR line diagnostics.Comment: Preprint submitted for publication 10/29/2
Euclid preparation. LXIV. The Cosmic Dawn Survey (DAWN) of the Euclid Deep and Auxiliary Fields
No full textPublisher Copyright: © 2025 The Authors.Euclid will provide deep near-infrared (NIR) imaging to ∼26.5 AB magnitude over ∼59 deg2 in its deep and auxiliary fields. The Cosmic DAWN survey combines dedicated and archival UV- NIR observations to provide matched depth multiwavelength imaging of the Euclid deep and auxiliary fields. The DAWN survey will provide consistently measured Euclid NIR-selected photometric catalogues, accurate photometric redshifts, and measurements of galaxy properties to a redshift of z ∼ 10. The DAWN catalogues include Spitzer IRAC data that are critical for stellar mass measurements at z ≳ 2.5 and high-z science. These catalogues complement the standard Euclid catalogues, which will not include Spitzer IRAC data. In this paper, we present an overview of the survey, including the footprints of the survey fields, the existing and planned observations, and the primary science goals for the combined data set.Peer reviewe
Large-scale Structures in the CANDELS Fields: The Role of the Environment in Star Formation Activity
No full textWe present a robust method, weighted von Mises kernel density estimation, along with boundary correction to reconstruct the underlying number density field of galaxies. We apply this method to galaxies brighter than Hubble Space Telescope /F160w ≤ 26 AB mag in the redshift range 0.4 ≤ z ≤ 5 in the five CANDELS fields (GOODS-N, GOODS-S, EGS, UDS, and COSMOS). We then use these measurements to explore the environmental dependence of the star formation activity of galaxies. We find strong evidence of environmental quenching for massive galaxies (M ≳ 10¹¹ M_⊙) out to z ~ 3.5 such that an overdense environment hosts ≳20% more massive quiescent galaxies than an underdense region. We also find that environmental quenching efficiency grows with stellar mass and reaches ~60% for massive galaxies at z ~ 0.5. The environmental quenching is also more efficient than stellar mass quenching for low-mass galaxies (M ≾ 10¹⁰ M_⊙) at low and intermediate redshifts (z ≾ 1.2). Our findings concur thoroughly with the "overconsumption" quenching model where the termination of cool gas accretion (cosmological starvation) happens in an overdense environment and the galaxy starts to consume its remaining gas reservoir in depletion time. The depletion time depends on the stellar mass and could explain the evolution of environmental quenching efficiency with stellar mass
Spectroscopic confirmation of a Coma Cluster progenitor at z~2.2
No full textWe report the spectroscopic confirmation of a new protocluster in the COSMOS field at z ∼ 2.2, originally identified as an overdensity of narrow-band selected Hα emitting candidates. With only two masks of Keck/MOSFIRE near-IR spectroscopy in both H (∼ 1.47-1.81 μm) and K (∼ 1.92- 2.40 μm) bands (∼ 1.5 hour each), we confirm 35 unique protocluster members with at least two emission lines detected with S/N > 3. Combined with 12 extra members from the zCOSMOS-deep spectroscopic survey (47 in total), we estimate a mean redshift, line-of-sight velocity dispersion, and total mass of zmean=2.23224 ± 0.00101, σlos=645 ± 69 km s−1, and Mvir ∼ (1 − 2)×10^14 M⊙ for this protocluster, respectively. We estimate a number density enhancement of δg ∼ 7 for this system and we argue that the structure is likely not virialized at z ∼ 2.2. However, in a spherical collapse model, δg is expected to grow to a linear matter enhancement of ∼ 1.9 by z=0, exceeding the collapse threshold of 1.69, and leading to a fully collapsed and virialized Coma-type structure with a total mass of Mdyn(z=0) ∼ 9.2×10^14 M⊙ by now. This observationally efficient confirmation suggests that large narrow-band emission-line galaxy surveys, when combined with ancillary photometric data, can be used to effectively trace the large-scale structure and protoclusters at a time when they are mostly dominated by star-forming galaxies
The clustering of typical Ly emitters from : host halo masses depend on Ly and UV luminosities
No full textWe investigate the clustering and halo properties of Ly-selected emission line galaxies (LAEs) from the Slicing COSMOS 4K (SC4K) and from archival NB497 imaging of SA22 split in 15 discrete redshift slices between . We measure clustering lengths of Mpc and typical halo masses of M for our narrowband-selected LAEs with typical erg s. The intermediate band-selected LAEs are observed to have Mpc with typical halo masses of M and typical erg s. We find a strong, redshift-independent correlation between halo mass and Ly luminosity normalized by the characteristic Ly luminosity, . The faintest LAEs () typically identified by deep narrowband surveys are found in M halos and the brightest LAEs () are found in M halos. A dependency on the rest-frame 1500 \AA~UV luminosity, M_\rm{UV}, is also observed where the halo masses increase from to M for M_\rm{UV} \sim -19 to mag. Halo mass is also observed to increase from to M for dust-corrected UV star formation rates from to M yr and continues to increase up to M in halo mass, where the majority of those sources are AGN. All the trends we observe are found to be redshift-independent. Our results reveal that LAEs are the likely progenitors of a wide range of galaxies depending on their luminosity, from dwarf-like, to Milky Way-type, to bright cluster galaxies. LAEs therefore provide unique insight into the early formation and evolution of the galaxies we observe in the local Universe
- …
