Abstract
We make use of Atacama Large Millimeter/submillimeter Array continuum observations of 15 luminous Lyman-break galaxies at
z
∼ 7–8 to probe their dust-obscured star formation. These ...observations are sensitive enough to probe obscured star formation rates (SFRs) of 20
M
⊙
yr
−1
(3
σ
). Six of the targeted galaxies show significant (≥3
σ
) dust-continuum detections, more than doubling the number of known dust-detected galaxies at
z
> 6.5. Their IR luminosities range from 2.7 × 10
11
L
⊙
to 1.1 × 10
12
L
⊙
, equivalent to obscured SFRs of 25 to 101
M
⊙
yr
−1
. We use our results to quantify the correlation of the infrared excess (IRX) on the UV-continuum slope
β
UV
and stellar mass. Our results are most consistent with a Small Magellanic Cloud (SMC) attenuation curve for intrinsic UV-slopes
β
UV
,
intr
of −2.63 and most consistent with an attenuation curve in between SMC and Calzetti for
β
UV
,
intr
slopes of −2.23, assuming a dust temperature
T
d
of 50 K. Our fiducial IRX–stellar mass results at
z
∼ 7–8 are consistent with marginal evolution from
z
∼ 0. We then show how both results depend on
T
d
. For our six dust-detected sources, we estimate their dust masses and find that they are consistent with dust production from supernovae if the dust destruction is low (<90%). Finally we determine the contribution of dust-obscured star formation to the SFR density for UV luminous (
H
<−21.5 mag: ≳1.7
L
*
UV
)
z
∼ 7–8 galaxies, finding that the total SFR density at
z
∼ 7 and
z
∼ 8 from bright galaxies is
0.20
−
0.10
+
0.10
dex and
0.23
−
0.09
+
0.06
dex higher, respectively; i.e., ∼
1
3
of the star formation in ≳1.7
L
*
UV
galaxies at
z
∼ 7–8 is obscured by dust.
ABSTRACT
We present catalogues of stellar masses, star formation rates (SFRs), and ancillary stellar population parameters for galaxies spanning 0 < z < 9 from the Deep Extragalactic VIsible Legacy ...Survey (DEVILS). DEVILS is a deep spectroscopic redshift survey with very high completeness, covering several premier deep fields including COSMOS (D10). Our stellar mass and SFR estimates are self-consistently derived using the spectral energy distribution (SED) modelling code ProSpect, using well-motivated parametrizations for dust attenuation, star formation histories, and metallicity evolution. We show how these improvements, and especially our physically motivated assumptions about metallicity evolution, have an appreciable systematic effect on the inferred stellar masses, at the level of ∼0.2 dex. To illustrate the scientific value of these data, we map the evolving galaxy stellar mass function (SMF) and the SFR–M⋆ relation for 0 < z < 4.25. In agreement with past studies, we find that most of the evolution in the SMF is driven by the characteristic density parameter, with little evolution in the characteristic mass and low-mass slopes. Where the SFR–M⋆ relation is indistinguishable from a power law at z > 2.6, we see evidence of a bend in the relation at low redshifts (z < 0.45). This suggests evolution in both the normalization and shape of the SFR–M⋆ relation since cosmic noon. It is significant that we only clearly see this bend when combining our new DEVILS measurements with consistently derived values for lower redshift galaxies from the Galaxy And Mass Assembly (GAMA) survey: this shows the power of having consistent treatment for galaxies at all redshifts.
ABSTRACT
We analyse the metallicity histories of ∼4500 galaxies from the GAMA survey at z < 0.06 modelled by the SED-fitting code ProSpect using an evolving metallicity implementation. These ...metallicity histories, in combination with the associated star formation histories, allow us to analyse the inferred gas-phase mass–metallicity relation. Furthermore, we extract the mass–metallicity relation at a sequence of epochs in cosmic history, to track the evolving mass–metallicity relation with time. Through comparison with observations of gas-phase metallicity over a large range of redshifts, we show that, remarkably, our forensic SED analysis has produced an evolving mass–metallicity relationship that is consistent with observations at all epochs. We additionally analyse the three-dimensional mass–metallicity–SFR space, showing that galaxies occupy a clearly defined plane. This plane is shown to be subtly evolving, displaying an increased tilt with time caused by general enrichment, and also the slowing down of star formation with cosmic time. This evolution is most apparent at lookback times greater than 7 Gyr. The trends in metallicity recovered in this work highlight that the evolving metallicity implementation used within the SED-fitting code ProSpect produces reasonable metallicity results over the history of a galaxy. This is expected to provide a significant improvement to the accuracy of the SED-fitting outputs.
We have examined the resolved stellar populations at large galactocentric distances along the minor axis (from 10 kpc up to between 40 and 75 kpc), with limited major axis coverage, of six nearby ...highly inclined Milky Way (MW) mass disc galaxies using Hubble Space Telescope data from the Galaxy haloes, Outer discs, Substructure, Thick discs, and Star clusters (GHOSTS) survey. We select red giant branch stars to derive stellar halo density profiles. The projected minor axis density profiles can be approximated by power laws with projected slopes of -2 to -3.7 and a diversity of stellar halo masses of 1-6 x 10 super( 9) M..., or 2-14 per cent of the total galaxy stellar masses. The typical intrinsic scatter around a smooth power-law fit is 0.05-0.1 dex owing to substructure. By comparing the minor and major axis profiles, we infer projected axis ratios c/a at ~25 kpc between 0.4 and 0.75. The GHOSTS stellar haloes are diverse, lying between the extremes charted out by the (rather atypical) haloes of the MW and M31. We find a strong correlation between the stellar halo metallicities and the stellar halo masses. We compare our results with cosmological models, finding good agreement between our observations and accretion-only models where the stellar haloes are formed by the disruption of dwarf satellites. In particular, the strong observed correlation between stellar halo metallicity and mass is naturally reproduced. Low-resolution hydrodynamical models have unrealistically high stellar halo masses. Current high-resolution hydrodynamical models appear to predict stellar halo masses somewhat higher than observed but with reasonable metallicities, metallicity gradients, and density profiles. (ProQuest: ... denotes formulae/symbols omitted.)
The earliest galaxies are thought to have emerged during the first billion years of cosmic history, initiating the ionization of the neutral hydrogen that pervaded the Universe at this time. Studying ...this 'epoch of reionization' involves looking for the spectral signatures of ancient galaxies that are, owing to the expansion of the Universe, now very distant from Earth and therefore exhibit large redshifts. However, finding these spectral fingerprints is challenging. One spectral characteristic of ancient and distant galaxies is strong hydrogen-emission lines (known as Lyman-α lines), but the neutral intergalactic medium that was present early in the epoch of reionization scatters such Lyman-α photons. Another potential spectral identifier is the line at wavelength 157.4 micrometres of the singly ionized state of carbon (the C ii λ = 157.74 μm line), which signifies cooling gas and is expected to have been bright in the early Universe. However, so far Lyman-α-emitting galaxies from the epoch of reionization have demonstrated much fainter C ii luminosities than would be expected from local scaling relations, and searches for the C ii line in sources without Lyman-α emission but with photometric redshifts greater than 6 (corresponding to the first billion years of the Universe) have been unsuccessful. Here we identify C ii λ = 157.74 μm emission from two sources that we selected as high-redshift candidates on the basis of near-infrared photometry; we confirm that these sources are two galaxies at redshifts of z = 6.8540 ± 0.0003 and z = 6.8076 ± 0.0002. Notably, the luminosity of the C ii line from these galaxies is higher than that found previously in star-forming galaxies with redshifts greater than 6.5. The luminous and extended C ii lines reveal clear velocity gradients that, if interpreted as rotation, would indicate that these galaxies have similar dynamic properties to the turbulent yet rotation-dominated disks that have been observed in Hα-emitting galaxies two billion years later, at 'cosmic noon'.
Full text
Available for:
IJS, KISLJ, NUK, SBMB, UL, UM, UPUK
Abstract
We report the discovery of a candidate galaxy with a photo-
z
of
z
∼ 12 in the first epoch of the James Webb Space Telescope (JWST) Cosmic Evolution Early Release Science Survey. Following ...conservative selection criteria, we identify a source with a robust
z
phot
=
11.8
−
0.2
+
0.3
(1
σ
uncertainty) with
m
F200W
= 27.3 and ≳7
σ
detections in five filters. The source is not detected at
λ
< 1.4
μ
m in deep imaging from both Hubble Space Telescope (HST) and JWST and has faint ∼3
σ
detections in JWST F150W and HST F160W, which signal a Ly
α
break near the red edge of both filters, implying
z
∼ 12. This object (Maisie’s Galaxy) exhibits F115W − F200W > 1.9 mag (2
σ
lower limit) with a blue continuum slope, resulting in 99.6% of the photo-
z
probability distribution function favoring
z
> 11. All data-quality images show no artifacts at the candidate’s position, and independent analyses consistently find a strong preference for
z
> 11. Its colors are inconsistent with Galactic stars, and it is resolved (
r
h
= 340 ± 14 pc). Maisie’s Galaxy has log
M
*
/
M
⊙
∼ 8.5 and is highly star-forming (log sSFR ∼ −8.2 yr
−1
), with a blue rest-UV color (
β
∼ −2.5) indicating little dust, though not extremely low metallicity. While the presence of this source is in tension with most predictions, it agrees with empirical extrapolations assuming UV luminosity functions that smoothly decline with increasing redshift. Should follow-up spectroscopy validate this redshift, our universe was already aglow with galaxies less than 400 Myr after the Big Bang.
Abstract
The selection of high-redshift galaxies often involves spectral energy distribution (SED) fitting to photometric data, an expectation for contamination levels, and measurement of sample ...completeness—all vetted through comparison to spectroscopic redshift measurements of a sub-sample. The first JWST data are now being taken over several extragalactic fields to different depths and across various areas, which will be ideal for the discovery and classification of galaxies out to distances previously uncharted. As spectroscopic redshift measurements for sources in this epoch will not be initially available to compare with the first photometric measurements of
z
> 8 galaxies, robust photometric redshifts are of the utmost importance. Galaxies at
z
> 8 are expected to have bluer rest-frame ultraviolet (UV) colors than typically used model SED templates, which could lead to catastrophic photometric redshift failures. We use a combination of BPASS and
Cloudy
models to create a supporting set of templates that match the predicted rest-UV colors of
z
> 8 simulated galaxies. We test these new templates by fitting simulated galaxies in a mock catalog, Yung et al., which mimic expected field depths and areas of the JWST Cosmic Evolution Early Release Science Survey (
m
5
σ
∼ 28.6 over ∼100 arcmin
2
). We use EAZY to highlight the improvements in redshift recovery with the inclusion of our new template set and suggest criteria for selecting galaxies at 8 <
z
< 10 with the JWST, providing an important test case for observers venturing into this new era of astronomy.
We present the Super Eight galaxies-a set of very luminous, high-redshift (7.1 < z < 8.0) galaxy candidates found in the Brightest of Reionizing Galaxies (BoRG) Survey fields. The original sample ...includes eight galaxies that are Y-band dropout objects with H-band magnitudes of mH < 25.5. Four of these objects were originally reported in Calvi et al. Combining new Hubble Space Telescope (HST) WFC3/F814W imaging and Spitzer IRAC data with archival imaging from BoRG and other surveys, we explore the properties of these galaxies. Photometric redshift fitting places six of these galaxies in the redshift range of 7.1 < z < 8.0, resulting in three new high-redshift galaxies and confirming three of the four high-redshift galaxy candidates from Calvi et al. We calculate the half-light radii of the Super Eight galaxies using the HST F160W filter and find that the Super Eight sizes are in line with the typical evolution of size with redshift. The Super Eights have a mean mass of log (M*/M ) ∼10, which is typical for sources in this luminosity range. Finally, we place our sample on the UV z ∼ 8 luminosity function and find that the Super Eight number density is consistent with other surveys in this magnitude and redshift range.
Abstract
We present a catalog of about 25,000 images of massive (
M
⋆
≥ 10
9
M
⊙
) galaxies at redshifts 3 ≤
z
≤ 6 from the TNG50 cosmological simulation, tailored for observations at multiple ...wavelengths carried out with JWST. The synthetic images were created with the SKIRT radiative transfer code, including the effects of dust attenuation and scattering. The noiseless images were processed with the
mirage
simulator to mimic the Near Infrared Camera (NIRCam) observational strategy (e.g., noise, dithering pattern, etc.) of the Cosmic Evolution Early Release Science (CEERS) survey. In this paper, we analyse the predictions of the TNG50 simulation for the size evolution of galaxies at 3 ≤
z
≤ 6 and the expectations for CEERS to probe that evolution. In particular, we investigate how sizes depend on the wavelength, redshift, mass, and angular resolution of the images. We find that the effective radius accurately describes the three-dimensional half-mass–radius of the TNG50 galaxies. Sizes observed at 2
μ
m are consistent with those measured at 3.56
μ
m at all redshifts and masses. At all masses, the population of higher-
z
galaxies is more compact than their lower-
z
counterparts. However, the intrinsic sizes are smaller than the mock observed sizes for the most massive galaxies, especially at
z
≲ 4. This discrepancy between the mass and light distributions may point to a transition in the galaxy morphology at
z
= 4–5, where massive compact systems start to develop more extended stellar structures.
22
22
Data publicly released at
https://www.tng-project.org/costantin22
.
We report an expanded sample of visual morphological classifications from the Galaxy and Mass Assembly survey phase two, which now includes 7556 objects (previously 3727 in phase one). We define a ...local (z < 0.06) sample and classify galaxies into E, S0-Sa, SB0-SBa, Sab-Scd, SBab-SBcd, Sd-Irr, and ‘little blue spheroid’ types. Using these updated classifications, we derive stellar mass function fits to individual galaxy populations divided both by morphological class and more general spheroid- or disc-dominated categories with a lower mass limit of log(M
*/M⊙) = 8 (one dex below earlier morphological mass function determinations). We find that all individual morphological classes and the combined spheroid-/bulge-dominated classes are well described by single Schechter stellar mass function forms. We find that the total stellar mass densities for individual galaxy populations and for the entire galaxy population are bounded within our stellar mass limits and derive an estimated total stellar mass density of ρ* = 2.5 × 108 M⊙ Mpc−3 h
0.7, which corresponds to an approximately 4 per cent fraction of baryons found in stars. The mass contributions to this total stellar mass density by galaxies that are dominated by spheroidal components (E and S0-Sa classes) and by disc components (Sab-Scd and Sd-Irr classes) are approximately 70 and 30 per cent, respectively.
PDF
![Rotation in [C ii]-emitting...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0028-0836/small "Rotation in [C ii]-emitting gas in two galaxies at a redshift of 6.8")
