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
S. Mascia
L. Pentericci
A. Calabro'
T. Treu
P. Santini
L. Yang
L. Napolitano
G. Roberts-Borsani
P. Bergamini
C. Grillo
P. Rosati
B. Vulcani
M. Castellano
K. Boyett
A. Fontana
K. Glazebrook
A. Henry
C. Mason
E. Merlin
T. Morishita
摘要： The escape fraction of Lyman-continuum (LyC) photons ($f_{esc}$) is a key parameter for determining the sources of cosmic reionization at $z\geq 6$. At these redshifts, owing to the opacity of the intergalactic medium, the LyC emission cannot be measured directly. However, LyC leakers during the epoch of reionization could be identified using indirect indicators that have been extensively tested at low and intermediate redshifts. These include a high [OIII]/[OII] flux ratio, high star-formation surface density, and compact sizes. In this work, we present observations of 29 $4.5 \leq z \leq 8$ gravitationally lensed galaxies in the Abell 2744 cluster field. From a combined analysis of JWST-NIRSpec and NIRCam data, we accurately derived their physical and spectroscopic properties: our galaxies have low masses $(\log(M_\star)\sim 8.5)$, blue UV spectral slopes ($\beta \sim -2.1$), compact sizes ($r_e \sim 0.3-0.5$ kpc), and high [OIII]/[OII] flux ratios. We confirm that these properties are similar to those characterizing low-redshift LyC leakers. Indirectly inferring the fraction of escaping ionizing photons, we find that more than 80% of our galaxies have predicted $f_{esc}$ values larger than 0.05, indicating that they would be considered leakers. The average predicted $f_{esc}$ value of our sample is 0.12, suggesting that similar galaxies at $z\geq 6$ have provided a substantial contribution to cosmic reionization.
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.
点击量
待评议
点击量
下载量
评论
