分类： 天文学 >> 天文学 提交时间： 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
摘要： 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$2$\mu \rm m$ boosted by a combination of the Balmer break and emission lines. The typical implied rest equivalent widths are $\sim200\unicode{0x212B}$ with some extreme objects up to $\sim 1000\unicode{0x212B}$. This is in contrast with brighter magnitudes where the red sources tend to be $z11$ galaxies and a very cool brown dwarf.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
A. Dressler
B. Vulcani
T. Treu
M. Rieke
C. Burns
A. Calabro'
A. Bonchi
M. Castellano
A. Fontana
N. Leethochawalit
C. Mason
E. Merlin
T. Morishita
D. Paris
A. Mercurio
T. Nanayakkara
B. M. Poggianti
P. Santini
X. Wang
K. Misselt
摘要： JWST observations of high redshift galaxies are used to measure their star formation histories - the buildup of stellar mass in the earliest galaxies. Here we use a novel analysis program, SEDz*, to compare near-IR spectral energy distributions for galaxies with redshifts 5 < z < 7 to combinations of stellar population templates evolved from z = 12. We exploit NIRCam imaging in 7 wide bands covering 1-5 mu m, taken in the context of the GLASS-JWST-ERS program, and use SEDz* to solve for well-constrained star formation histories for 24 exemplary galaxies. In this first look we find a variety of histories, from long, continuous star formation over 5 < z < 12 to short but intense starbursts - sometimes repeating, and, most commonly, contiguous mass buildup lasting ~ 0.5 Myr,possibly the seeds of today's typical, M* galaxies.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
M. Nonino
K. Glazebrook
A. J. Burgasser
G. Polenta
T. Morishita
M. Lepinzan
M. Castellano
A. Fontana
E. Merlin
A. Bonchi
D. Paris
T. Treu
B. Vulcani
X. Wang
P. Santini
E. Vanzella
T. Nanayakkara
A. Mercurio
P. Rosati
C. Grillo
摘要： We present the serendipitous discovery of a late T-type brown dwarf candidate in JWST NIRCam observations of the Early Release Science Abell 2744 parallel field. The discovery was enabled by the sensitivity of JWST at 4~$\mu$m wavelengths and the panchromatic 0.9--4.5~$\mu$m coverage of the spectral energy distribution. The unresolved point source has magnitudes F115W = 27.95$\pm$0.15 and F444W = 25.84$\pm$0.01 (AB), and its F115W$-$F444W and F356W$-$F444W colors match those expected for other, known T dwarfs. We can exclude it as a reddened background star, high redshift quasar, or very high redshift galaxy. Comparison with stellar atmospheric models indicates a temperature of $T_{eff}$ $\approx$ 600~K and surface gravity $\log{g}$ $\approx$ 5, implying a mass of 0.03~M$_{\odot}$ and age of 5~Gyr. We estimate the distance of this candidate to be 570--720~pc in a direction perpendicular to the Galactic plane, making it a likely thick disk or halo brown dwarf. These observations underscore the power of JWST to probe the very low-mass end of the substellar mass function in the Galactic thick disk and halo.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
N. Leethochawalit
M. Trenti
P. Santini
L. Yang
E. Merlin
M. Castellano
A. Fontana
T. Treu
C. Mason
K. Glazebrook
T. Jones
B. Vulcani
T. Nanayakkara
D. Marchesini
S. Mascia
T. Morishita
G. Roberts-Borsani
A. Bonchi
D. Paris
K. Boyett
摘要： We present the first James Webb Space Telescope/NIRCam-led determination of $79.5$. Their star formation main sequence is consistent with predictions from simulations. Lastly, we introduce an analytical framework to constrain main-sequence evolution at $z>7$ based on galaxy ages and basic assumptions, through which we find results consistent with expectations from cosmological simulations. While this work only gives a glimpse of the properties of typical galaxies that are thought to drive the reionization of the universe, it clearly shows the potential of JWST to unveil unprecedented details on galaxy formation in the first billion years.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Lilan Yang
T. Morishita
N. Leethochawalit
M. Castellano
A. Calabro
T. Treu
A. Bonchi
A. Fontana
C. Mason
E. Merlin
D. Paris
M. Trenti
G. Roberts-Borsani
M. Bradac
E. Vanzella
B. Vulcani
D. Marchesini
X. Ding
Themiya Nanayakkara
Simon Birrer
摘要： We present the first rest-frame optical size-luminosity relation of galaxies at $z>7$, using the NIRCam imaging data obtained by the GLASS James Webb Space Telescope Early Release Science (GLASS-JWST-ERS) program, providing the deepest extragalactic data of the ERS campaign. Our sample consist of 19 photometrically selected bright galaxies with $m_\text{F444W}\leq27.8$ at $77$. Given the limited sample size and magnitude range, we first fix the slope to that observed for larger samples in rest-frame UV using HST samples. The median size $r_0$ at the reference luminosity $M=-21$ decreases slightly from rest-frame optical ($600\pm80$ pc) to UV ($450\pm130$ pc). We then re-fit the size-luminosity relation allowing the slope to vary. The slope is consistent with $\beta\sim0.2$ for all bands except F150W, where we find a marginally steeper slope of $\beta=0.53\pm0.15$. The steep UV slope is mainly driven by the smallest and faintest galaxies. If confirmed by larger samples, it implies that the UV size-luminosity relation breaks toward the faint end as suggested by lensing studies.
分类： 天文学 >> 天文学 提交时间： 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
摘要： 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.
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