分类： 天文学 >> 天文学 提交时间： 2023-02-19
Amy Etherington
James W. Nightingale
Richard Massey
Sut-Ieng Tam
XiaoYue Cao
Anna Niemiec
Qiuhan He
Andrew Robertson
Ran Li
Aristeidis Amvrosiadis
Shaun Cole
Jose M. Diego
Carlos S. Frenk
Brenda L. Frye
David Harvey
Mathilde Jauzac
Anton M. Koekemoer
David J. Lagattuta
Marceau Limousin
Guillaume Mahler
摘要： The distribution of mass in galaxy-scale strong gravitational lenses is often modelled as an elliptical power law plus `external shear', which notionally accounts for neighbouring galaxies and cosmic shear. We show that it does not. Except in a handful of rare systems, the best-fit values of external shear do not correlate with independent measurements of shear: from weak lensing in 45 Hubble Space Telescope images, or in 50 mock images of lenses with complex distributions of mass. Instead, the best-fit shear is aligned with the major or minor axis of 88% of lens galaxies; and the amplitude of the external shear increases if that galaxy is disky. We conclude that `external shear' attached to a power law model is not physically meaningful, but a fudge to compensate for lack of model complexity. Since it biases other model parameters that are interpreted as physically meaningful in several science analyses (e.g. measuring galaxy evolution, dark matter physics or cosmological parameters), we recommend that future studies of galaxy-scale strong lensing should employ more flexible mass models.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Katriona M. L. Gould
Gabriel Brammer
Francesco Valentino
Katherine E. Whitaker
John R. Weaver
Claudia del P. Lagos
Francesca Rizzo
Maximilien Franco
Bau-Ching Hseih
Olivier Ilbert
Shuowen Jin
Georgios Magdis
Henry J. McCracken
Bahram Mobasher
Marko Shuntov
Charles L. Steinhardt
Victoria Strait
Sune Toft
摘要： We select and characterise a sample of massive
(log(M$_{*}/$M$_{\odot})>10.6$) quiescent galaxies (QGs) at $33$. We compute
median rest-frame SEDs for our sample and find the median quiescent galaxy at
$3
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Fengwu Sun
Eiichi Egami
Pablo G. Pérez-González
Ian Smail
Karina I. Caputi
Franz E. Bauer
Timothy D. Rawle
Seiji Fujimoto
Kotaro Kohno
Ugnė Dudzevičiūtė
Hakim Atek
Matteo Bianconi
Scott C. Chapman
Francoise Combes
Mathilde Jauzac
Jean-Baptiste Jolly
Anton M. Koekemoer
Georgios E. Magdis
Giulia Rodighiero
Wiphu Rujopakarn
摘要： We present a Spitzer/IRAC survey of H-faint ($H_{160} \gtrsim 26.4$, $<5\sigma$) sources in 101 lensing cluster fields. Across a CANDELS/Wide-like survey area of $\sim$648 arcmin$^2$ (effectively $\sim$221 arcmin$^2$ in the source plane), we have securely discovered 53 sources in the IRAC Channel-2 band (CH2, 4.5 $\mathrm{\mu m}$; median CH2$=22.46\pm0.11$ AB mag) that lack robust HST/WFC3-IR F160W counterparts. The most remarkable source in our sample, namely ES-009 in the field of Abell 2813, is the brightest H-faint galaxy at 4.5 $\mathrm{\mu m}$ known so far ($\mathrm{CH2}=20.48\pm0.03$ AB mag). We show that the H-faint sources in our sample are massive (median $M_\mathrm{star} = 10^{10.3\pm 0.3}$ $M_\odot$), star-forming (median star formation rate $=100_{-40}^{+60}$ $M_\odot$yr$^{-1}$) and dust-obscured ($A_V=2.6\pm0.3$) galaxies around a median photometric redshift of $z=3.9\pm0.4$. The stellar continua of 14 H-faint galaxies can be resolved in the CH2 band, suggesting a median circularized effective radius ($R_\mathrm{e,circ}$; lensing corrected) of $1.9\pm0.2$ kpc and $<1.5$ kpc for the resolved and whole samples, respectively. This is consistent with the sizes of massive unobscured galaxies at $z\sim4$, indicating that H-faint galaxies represent the dusty tail of the distribution of a wider galaxy population. Comparing with the ALMA dust continuum sizes of similar galaxies reported previously, we conclude that the heavy dust obscuration in H-faint galaxies is related to the compactness of both stellar and dust continua ($R_\mathrm{e,circ}\sim 1$ kpc). These H-faint galaxies make up $16_{-7}^{+13}$% of the galaxies in the stellar mass range of $10^{10}-10^{11.2}$ $M_\odot$ at $z=3\sim5$, contributing to $8_{-4}^{+8}$% of the cosmic star formation rate density in this epoch and likely tracing the early phase of massive galaxy formation.
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