Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Karl Glazebrook
T. Nanayakkara
C. Jacobs
N. Leethochawalit
A. Calabrò
A. Bonchi
M. Castellano
A. Fontana
C. Mason
E. Merlin
T. Morishita
D. Paris
M. Trenti
T. Treu
P. Santini
X. Wang
K. Boyett
Marusa Bradac
G. Brammer
T. Jones
Abstract： We present a first look at the reddest 2-5$\mu\rm m$ sources found in deep
images from the GLASS Early Release Science program. We undertake a general
search, i.e. not looking for any particular spectral signatures, for sources
detected only in bands redder than reachable with the Hubble Space Telescope,
and which would likely not have been identified in pre-JWST surveys. We search
for sources down to AB $\sim 27$ (corresponding to $>10\sigma$ detection
threshold) in any of the F200W to F444W filters,with a $>1$ magnitude excess
relative to F090W to F150W bands. Fainter than F444W$>25$ we find 56 such
sources of which 37 have reasonably constrained spectral energy distributions
to which we can fit photometric redshifts. We find the majority of this
population ($\sim$ 65%) as $2
Peer Review Status:
Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
A. Saldana-Lopez
D. Schaerer
J. Chisholm
A. Calabrò
L. Pentericci
A. Saxena
R. Amorín
A. C. Carnall
F. Fontanot
J. P. U. Fynbo
L. Guaita
N. P. Hathi
P. Hibon Z. Ji D. J. McLeod
E. Pompei
G. Zamorani
Abstract： To better understand the ionizing properties of galaxies in the EoR, we investigate deep, rest-frame ultraviolet (UV) spectra of $\simeq 500$ star-forming galaxies at $3 \leq z \leq 5$ selected from the public ESO-VANDELS spectroscopic survey. The absolute ionizing photon escape fraction ($f_{\rm esc}^{\rm abs}$) is derived by combining absorption line measurements with estimates of the UV attenuation. The ionizing production efficiency ($\xi_{ion}$) is calculated by fitting the far-UV (FUV) stellar continuum of the VANDELS galaxies. We find that the $f_{\rm esc}^{\rm abs}$ and $\xi_{ion}$ parameters increase towards low-mass, blue UV-continuum slopes and strong Ly$\alpha$ emitting galaxies, and both are just slightly higher-than-average for the UV-faintest galaxies in the sample. Potential Lyman Continuum Emitters (LCEs) and selected Lyman Alpha Emitters (LAEs) show systematically higher $\xi_{ion}$ ($\log \xi_{ion}$ (Hz\erg) $\approx 25.38, 25.41$) than non-LCEs and non-LAEs ($\log \xi_{ion}$ (Hz\erg) $\approx 25.18, 25.14$) at similar UV magnitudes. This indicates very young underlying stellar populations ($\approx 10~{\rm Myr}$) at relatively low metallicities ($\approx 0.2~{\rm Z_{\odot}}$). The FUV non-ionizing spectra of potential LCEs is characterized by very blue UV slopes ($\leq -2$), enhanced Ly$\alpha$ emission ($\leq -25$A), strong UV nebular lines (e.g., high CIV1550/CIII]1908 $\geq 0.75$ ratios), and weak absorption lines ($\leq 1$A). The latter suggests the existence of low gas-column-density channels in the interstellar medium which enables the escape of ionizing photons. By comparing our VANDELS results against other surveys in the literature, our findings imply that the ionizing budget in the EoR was likely dominated by UV-faint, low-mass and dustless galaxies.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
P. Santini
A. Fontana
M. Castellano
N. Leethochawalit
M. Trenti
T. Treu
D. Belfiori
S. Birrer
A. Bonchi
E. Merlin
C. Mason
T. Morishita
M. Nonino
D. Paris
G. Polenta
P. Rosati
L. Yang
M. Bradac
A. Calabrò
A. Dressler
Abstract： We exploit James Webb Space Telescope (JWST) NIRCam observations from the GLASS-JWST-Early Release Science program to investigate galaxy stellar masses at z>7. We first show that JWST observations reduce the uncertainties on the stellar mass by a factor of at least 5-10, when compared with the highest quality data sets available to date. We then study the UV mass-to-light ratio, finding that galaxies exhibit a two orders of magnitude range of M/L_UV values for a given luminosity, indicative of a broad variety of physical conditions and star formation histories. As a consequence, previous estimates of the cosmic star stellar mass density - based on an average correlation between UV luminosity and stellar mass - can be biased by as much as a factor of ~6. Our first exploration demonstrates that JWST represents a new era in our understanding of stellar masses at z>7, and therefore of the growth of galaxies prior to cosmic reionization.
Peer Review Status:Awaiting Review
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