ABSTRACT Although there has been much progress in understanding how galaxies evolve, we still do not understand how and when they stop forming stars and become quiescent. We address this by applying ...our galaxy spectral energy distribution models, which incorporate physically motivated star formation histories (SFHs) from cosmological simulations, to a sample of quiescent galaxies at . A total of 845 quiescent galaxies with multi-band photometry spanning rest-frame ultraviolet through near-infrared wavelengths are selected from the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) data set. We compute median SFHs of these galaxies in bins of stellar mass and redshift. At all redshifts and stellar masses, the median SFHs rise, reach a peak, and then decline to reach quiescence. At high redshift, we find that the rise and decline are fast, as expected, because the universe is young. At low redshift, the duration of these phases depends strongly on stellar mass. Low-mass galaxies ( ) grow on average slowly, take a long time to reach their peak of star formation ( Gyr), and then the declining phase is fast ( Gyr). Conversely, high-mass galaxies ( ) grow on average fast ( Gyr), and, after reaching their peak, decrease the star formation slowly ( ). These findings are consistent with galaxy stellar mass being a driving factor in determining how evolved galaxies are, with high-mass galaxies being the most evolved at any time (i.e., downsizing). The different durations we observe in the declining phases also suggest that low- and high-mass galaxies experience different quenching mechanisms, which operate on different timescales.
Abstract
We report on a search for the C
ii
158
μ
m emission line from galaxies associated with four high-metallicity damped Ly
α
absorbers (DLAs) at
z
∼ 4 using the Atacama Large ...Millimeter/submillimeter Array (ALMA). We detect C
ii
158
μ
m emission from galaxies at the DLA redshift in three fields, with one field showing two C
ii
158
μ
m emitters. Combined with previous results, we now have detected C
ii
158
μ
m emission from five of six galaxies associated with targeted high-metallicity DLAs at
z
∼ 4. The galaxies have relatively large impact parameters, ≈16–45 kpc, C
ii
158
μ
m line luminosities of (0.36–30) × 10
8
L
⊙
, and rest-frame far-infrared properties similar to those of luminous Lyman-break galaxies, with star formation rates of ≈7–110
M
⊙
yr
−1
. Comparing the absorption and emission line profiles yields a remarkable agreement between the line centroids, indicating that the DLA traces gas at velocities similar to that of the C
ii
158
μ
m emission. This disfavors a scenario where the DLA arises from gas in a companion galaxy. These observations highlight ALMA’s unique ability to uncover a high-redshift galaxy population that has largely eluded detection for decades.
We present an investigation of clumpy galaxies in the Hubble Ultra Deep Field at in the rest-frame far-ultraviolet (FUV) using Hubble Space Telescope Wide Field Camera 3 broadband imaging in F225W, ...F275W, and F336W. An analysis of 1404 galaxies yields 209 galaxies that host 403 kpc scale clumps. These host galaxies appear to be typical star-forming galaxies, with an average of 2 clumps per galaxy and reaching a maximum of 8 clumps. We measure the photometry of the clumps and determine the mass, age, and star formation rates (SFR) using the spectral energy distribution fitting code FAST. We find that clumps make an average contribution of 19% to the total rest-frame FUV flux of their host galaxy. Individually, clumps contribute a median of 5% to the host galaxy SFR and an average of ∼4% to the host galaxy mass, with total clump contributions to the host galaxy stellar mass ranging widely from lower than 1% up to 93%. Clumps in the outskirts of galaxies are typically younger, with higher SFRs, than clumps in the inner regions. The results are consistent with clump migration theories in which clumps form through violent gravitational instabilities in gas-rich turbulent disks, eventually migrate toward the center of the galaxies, and coalesce into the bulge.
Abstract
We present a sample of nine fast radio bursts (FRBs) from which we derive magnetic field strengths of the host galaxies represented by normal,
z
< 0.5 star-forming galaxies with stellar ...masses
M
*
≈ 10
8
–10
10.5
M
⊙
. We find no correlation between the FRB rotation measure (RM) and redshift, which indicates that the RM values are due mostly to the FRB host contribution. This assertion is further supported by a significant positive correlation (Spearman test probability
P
S
< 0.05) found between the RM and the estimated host dispersion measure (DM
host
; with Spearman rank correlation coefficient
r
S
= +0.75). For these nine galaxies, we estimate their magnetic field strengths projected along the sight line ∣
B
∥
∣, finding a low median value of 0.5
μ
G. This implies the magnetic fields of our sample of hosts are weaker than those characteristic of the solar neighborhood (≈6
μ
G), but relatively consistent with a lower limit on the observed range of ≈2–10
μ
G for star-forming disk galaxies, especially as we consider reversals in the
B
-field, and that we are only probing B
∥
. We compare to RMs from simulated galaxies of the Auriga project—magneto-hydrodynamic cosmological zoom simulations—and find that the simulations predict the observed values to within a 95% confidence interval. Upcoming FRB surveys will provide hundreds of new FRBs with high-precision localizations, RMs, and imaging follow-up to support further investigation into the magnetic fields of a diverse population of
z
< 1 galaxies.
Abstract The cycling of metals between interstellar gas and dust is a critical aspect of the baryon cycle of galaxies, yet our understanding of this process is limited. This study focuses on ...understanding dust depletion effects in the low-metallicity regime (<20% Z ⊙ ) typical of cosmic noon. Using medium-resolution UV spectroscopy from the Cosmic Origins Spectrograph on board the Hubble Space Telescope, gas-phase abundances and depletions of iron and sulfur were derived toward 18 sight lines in local dwarf galaxies IC 1613 and Sextans A. The results show that the depletion of Fe and S is consistent with that found in the Milky Way (MW), LMC, and SMC. The depletion level of Fe increases with gas column density, indicating dust growth in the interstellar medium. The level of Fe depletion decreases with decreasing metallicity, resulting in the fraction of iron in gas ranging from 3% in the MW to 9% in IC 1613 and ∼19% in Sextans A. The dust-to-gas and dust-to-metal ratios ( D / G , D / M ) for these dwarf galaxies were estimated based on the MW relations between the depletion of Fe and other elements. The study finds that D / G decreases only slightly sublinearly with metallicity, with D / M decreasing from 0.41 ± 0.05 in the MW to 0.11 ± 0.11 at 0.10 Z ⊙ (at log N (H) = 21 cm −2 ). The trend of D / G versus metallicity using depletion in local systems is similar to that inferred in Damped Ly α systems from abundance ratios but lies higher than the trend inferred from far-IR measurements in nearby galaxies.
Abstract We present Keck Cosmic Web Imager Ly α integral field spectroscopy of the fields surrounding 14 damped Ly α absorbers (DLAs) at z ≈ 2. Of these 14 DLAs, nine have high metallicities (M/H > − ...0.3), and four of those nine feature a CO-emitting galaxy at an impact parameter ≲30 kpc. Our search reaches median Ly α line flux sensitivities of ∼2 × 10 −17 erg s −1 cm −2 over apertures of ∼6 kpc and out to impact parameters of ∼50 kpc. We recover the Ly α flux of three known Ly α -emitting H i -selected galaxies in our sample. In addition, we find two Ly α emitters at impact parameters of ≈50–70 kpc from the high-metallicity DLA at z ≈ 1.96 toward QSO B0551-366. This field also contains a massive CO-emitting galaxy at an impact parameter of ≈15 kpc. Apart from the field with QSO B0551-366, we do not detect significant Ly α emission in any of the remaining eight high-metallicity DLA fields. Considering the depth of our observations and our ability to recover previously known Ly α emitters, we conclude that H i -selected galaxies associated with high-metallicity DLAs at z ≈ 2 are dusty and therefore might feature low Ly α escape fractions. Our results indicate that complementary approaches—using Ly α , CO, H α , and C ii 158 μ m emission—are necessary to identify the wide range of galaxy types associated with z ≈ 2 DLAs.
ABSTRACT We present estimates of intrinsic scatter in the star formation rate (SFR)-stellar mass (M*) correlation in the redshift range and in the mass range M . We utilize photometry in the Hubble ...Ultradeep Field (HUDF12) and Ultraviolet Ultra Deep Field (UVUDF) campaigns and CANDELS/GOODS-S and estimate SFR, M* from broadband spectral energy distributions and the best-available redshifts. The maximum depth of the UDF photometry (F160W 29.9 AB, 5 depth) probes the SFR-M* correlation down to 107M , a factor of 10-100× lower in M* than previous studies, and comparable to dwarf galaxies in the local universe. We find the slope of the SFR-M* relationship to be near unity at all redshifts and the normalization to decrease with cosmic time. We find a moderate increase in intrinsic scatter with cosmic time from 0.2 to 0.4 dex across the epoch of peak cosmic star formation. None of our redshift bins show a statistically significant increase in intrinsic scatter at low mass. However, it remains possible that intrinsic scatter increases at low mass on timescales shorter than ∼100 Myr. Our results are consistent with a picture of gradual and self-similar assembly of galaxies across more than three orders of magnitude in stellar mass from as low as 107M .
Abstract
We present deep UV imaging observations of the Great Observatories Origins Survey Northern (GOODS-N) field with AstroSat/UVIT (AstroSat UV Deep Field north—AUDFn), using one far-UV (FUV) ...(F154W, 34.0 ks) and two near-UV (NUV) filters (N242W, 19.2 ks; N245M, 15.5 ks). The nature of the UV sky background was explored across the UVIT field, and a global mean and rms were estimated for each filter. We reach 3
σ
detection limits of
m
AB
∼ 27.35, 27.28, and 27.02 mag for a point source in the F154W, N242W, and N245M bands respectively. The 50% completeness limits of the FUV and NUV images are
m
AB
= 26.40 and 27.05 mag respectively. We constructed point-spread functions for each band and estimated their FWHM, which were found to be almost the same: 1.″18 in F154W, 1.″11 in N242W, and 1.″24 in N245M. We used SExtractor to separately identify sources in the FUV and NUV filters and produce the UV source catalog of the entire AUDFn field. The source count slope estimated in FUV and NUV is 0.57 dex mag
−1
(between 19 and 25 mag) and 0.44 dex mag
−1
(between 18 and 25 mag), respectively. The catalog contains 6839 and 16,171 sources (brighter than the 50% completeness limit) in the FUV and NUV, respectively. Our FUV and NUV flux measurements of the identified sources complement existing multiband data in the GOODS-N field, and enable us to probe rest-frame FUV properties of galaxies at redshift
z
< 1 and search for candidate Lyman continuum leakers at redshift
z
> 0.97.
We present near-infrared emission line counts and luminosity functions from the Hubble Space Telescope Wide Field Camera 3 Infrared Spectroscopic Parallels (WISP) program for 29 fields (0.037 deg ...super(2)) observed using both the G102 and G141 grism. We use simulations to correct for significant (>20%) incompleteness introduced in part by the non-dithered, non-rotated nature of the grism parallels. Our H alpha luminosity function contains a comparable number density of faint line emitters to that found by the Near IR Camera and Multi-Object Spectrometer near-infrared grism surveys, but significantly fewer (factors of 3-4 less) high-luminosity emitters. We also find that our high-redshift (z = 0.9-1.5) counts are in agreement with the high-redshift (z = 1.47) narrowband H alpha survey of HiZELS (Sobral et al.), while our lower redshift luminosity function (z = 0.3-0.9) falls slightly below their z = 0.84 result.
We present the rest-1500 UV luminosity functions (LF) for star-forming galaxies during the cosmic high noon-the peak of cosmic star formation rate at . We use deep NUV imaging data obtained as part ...of the Hubble Ultra-Violet Ultra Deep Field (UVUDF) program, along with existing deep optical and NIR coverage on the HUDF. We select F225W, F275W, and F336W dropout samples using the Lyman break technique, along with samples in the corresponding redshift ranges selected using photometric redshifts, and measure the rest-frame UV LF at , respectively, using the modified maximum likelihood estimator. We perform simulations to quantify the survey and sample incompleteness for the UVUDF samples to correct the effective volume calculations for the LF. We select galaxies down to and fit a faint-end slope of at , , and , respectively. We compare the star formation properties of galaxies from these UV observations with results from H and UV+IR observations. We find a lack of high-SFR sources in the UV LF compared to the H and UV+IR, likely due to dusty SFGs not being properly accounted for by the generic relation used to correct for dust. We compute a volume-averaged UV-to-H ratio by abundance matching the rest-frame UV LF and H LF. We find an increasing UV-to-H ratio toward low-mass galaxies ( ). We conclude that this could be due to a larger contribution from starbursting galaxies compared to the high-mass end.
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![[C ii] 158 μm Emission from...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/2041-8205_2041-8213/small "[C ii] 158 μm Emission from z ∼ 4 H i Absorption-selected Galaxies")
