19 research outputs found
Revealing components of the galaxy population through nonparametric techniques
The distributions of galaxy properties vary with environment, and are often
multimodal, suggesting that the galaxy population may be a combination of
multiple components. The behaviour of these components versus environment holds
details about the processes of galaxy development. To release this information
we apply a novel, nonparametric statistical technique, identifying four
components present in the distribution of galaxy H emission-line
equivalent-widths. We interpret these components as passive, star-forming, and
two varieties of active galactic nuclei. Independent of this interpretation,
the properties of each component are remarkably constant as a function of
environment. Only their relative proportions display substantial variation. The
galaxy population thus appears to comprise distinct components which are
individually independent of environment, with galaxies rapidly transitioning
between components as they move into denser environments.Comment: 12 pages, 10 figures, accepted for publication in MNRA
EPOCHS Paper II: The Ultraviolet Luminosity Function from using 110 square arcminutes of deep, blank-field data from the PEARLS Survey and Public Science Programmes
We present an analysis of the ultraviolet luminosity function (UV LF) and
star formation rate density of distant galaxies () in the
`blank' fields of the Prime Extragalactic Areas for Reionization Science
(PEARLS) survey combined with Early Release Science (ERS) data from the CEERS,
GLASS and NGDEEP surveys/fields. We use a combination of SED fitting tools and
quality cuts to obtain a reliable selection and characterisation of
high-redshift () galaxies from a consistently processed set of deep,
near-infrared imaging. Within an area of 110 arcmin, we identify 214
candidate galaxies at redshifts and we use this sample to study the
ultraviolet luminosity function (UV LF) in four redshift bins between
. The measured number density of galaxies at and match
those of past observations undertaken by the em Hubble Space Telescope (HST).
However, towards higher redshifts we find that the evolution of the UV LF is
mild, resulting in higher measured number densities of UV luminous galaxies at
and compared to predictions from simulations and past HST
observations. When examining the star formation rate density of galaxies at
this time period, our observations are still consistent with a constant star
formation efficiency, are slightly lower than previous early estimations using
JWST and support galaxy driven reionization at .Comment: 28 Pages, 4 Tables, 9 Figures, Submitted to Ap
JWSTās PEARLS: A new lens model for ACT-CL J0102ā4915, āEl Gordo,ā and the first red supergiant star at cosmological distances discovered by JWST
The first James Webb Space Telescope (JWST) data on the massive colliding cluster El Gordo allow for 23 known families of multiply lensed images to be confirmed and for eight new members of these families to be identified. Based on these families, which have been confirmed spectroscopically by MUSE, we derived an initial lens model. This model guided the identification of 37 additional families of multiply lensed galaxies, among which 28 are entirely new systems, and nine were previously known. The initial lens model determined geometric redshifts for the 37 new systems. The geometric redshifts agree reasonably well with spectroscopic or photometric redshifts when those are available. The geometric redshifts enable two additional models that include all 60 families of multiply lensed galaxies spanning a redshift range 2āā0.8 and has an estimated virial mass close the maximum mass allowed by standard cosmological models. The JWST images also reveal the presence of small-mass perturbers that produce small lensing distortions. The smallest of these is consistent with being a dwarf galaxy at zā=ā0.87 and has an estimated mass of 3.8ā
Ćā
109 Mā, making it the smallest substructure found at zā>ā0.5. The JWST images also show several candidate caustic-crossing events. One of them is detected at high significance at the expected position of the critical curve and is likely a red supergiant star at zā=ā2.1878. This would be the first red supergiant found at cosmological distances. The cluster lensing should magnify background objects at zā>ā6, making more of them visible than in blank fields of a similar size, but there appears to be a deficiency of such objects.J.M.D. acknowledges the support of project PGC2018-101814-B-100 (MCIU/AEI/MINECO/FEDER, UE) Ministerio de Ciencia, InvestigaciĆ³n y Universidades. This project was funded by the Agencia Estatal de InvestigaciĆ³n, Unidad de Excelencia MarĆa de Maeztu, ref. MDM-2017-0765. AZ and AKM acknowledge support by Grant No. 2020750 from the United States-Israel Binational Science Foundation (BSF) and Grant No. 2109066 from the United States National Science Foundation (NSF), and by the Ministry of Science & Technology, Israel. RAW, SHC, and RAJ acknowledge support from NASA JWST Interdisciplinary Scientist grants NAG5-12460, NNX14AN10G and 80NSSC18K0200 from GSFC. EZ acknowledges funding from the Swedish National Space Agency. Work by CJC acknowledges support from the European Research Council (ERC) Advanced Investigator Grant EPOCHS (788113). LD acknowledges the research grant support from the Alfred P. Sloan Foundation (Award Number FG-2021-16495). BLF thanks the Berkeley Center for Theoretical Physics for their hospitality during the writing of this paper. MAM acknowledges the support of a National Research Council of Canada Plaskett Fellowship, and the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE17010001. CNAW acknowledges funding from the JWST/NIRCam contract NASS-0215 to the University of Arizona. GBC acknowledges the Max Planck Society for financial support through the Max Planck Research Group for S. H. Suyu and the academic support from the German Centre for Cosmological Lensing.Peer reviewe
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Rise and fall of the Beringian steppe bison.
The widespread extinctions of large mammals at the end of the Pleistocene epoch have often been attributed to the depredations of humans; here we present genetic evidence that questions this assumption. We used ancient DNA and Bayesian techniques to reconstruct a detailed genetic history of bison throughout the late Pleistocene and Holocene epochs. Our analyses depict a large diverse population living throughout Beringia until around 37,000 years before the present, when the population's genetic diversity began to decline dramatically. The timing of this decline correlates with environmental changes associated with the onset of the last glacial cycle, whereas archaeological evidence does not support the presence of large populations of humans in Eastern Beringia until more than 15,000 years later