Tootfinder

Dramatic Drop in the X-Ray Polarization of Swift J1727.8$-$1613 in the Soft Spectral State
Ji\v{r}\'i Svoboda, Michal Dov\v{c}iak, James F. Steiner, Philip Kaaret, Jakub Podgorn\'y, Juri Poutanen, Alexandra Veledina, Fabio Muleri, Roberto Taverna, Henric Krawczynski, Ma\"imouna Brigitte, Sudeb Ranjan Datta, Stefano Bianchi, Noel Castro Segura, Javier A. Garc\'ia, Adam Ingram, Giorgio Matt, Teo Mu\~noz-Darias, Edward Nathan, Martin C. Weisskopf, Diego Altamirano, Luca B…

Dramatic Drop in the X-Ray Polarization of Swift J1727.8$-$1613 in the Soft Spectral State
Black-hole X-ray binaries exhibit different spectral and timing properties in different accretion states. The X-ray outburst of a recently discovered and extraordinarily bright source, Swift$~$J1727.8$-$1613, has enabled the first investigation of how the X-ray polarization properties of a source evolve with spectral state. The 2$-$8 keV polarization degree was previously measured by the Imaging X-ray Polarimetry Explorer (IXPE) to be $\approx$ 4% in the hard and hard intermediate states. Here …

JWST PRIMER: A new multi-field determination of the evolving galaxy UV luminosity function at redshifts $\mathbf{z \simeq 9-15}$
C. T. Donnan, R. J. McLure, J. S. Dunlop, D. J. McLeod, D. Magee, K. Z. Arellano-C\'ordova, L. Barrufet, R. Begley, R. A. A. Bowler, A. C. Carnall, F. Cullen, R. S. Ellis, A. Fontana, G. D. Illingworth, N. A. Grogin, M. L. Hamadouche, A. M. Koekemoer, Feng-Yuan Liu, C. Mason, P. Santini, T. M. Stanton
https://arxiv.org/abs/2403.03171 https://arxiv.org/pdf/2403.03171
arXiv:2403.03171v1 Announce Type: new
Abstract: We present a new determination of the evolving galaxy UV luminosity function (LF) over the redshift range $8.5<15.5$ using a combination of several major Cycle-1 JWST imaging programmes - PRIMER, JADES and NGDEEP. This multi-field approach yields a total of $\simeq370$ sq. arcmin of JWST/NIRCam imaging, reaching (5-$\sigma$) depths of $\simeq30$ AB mag in the deepest regions. We select a sample of 2548 galaxies with a significant probability of lying at high redshift ($p(z>8.5)>0.05$) to undertake a statistical calculation of the evolving UV LF. Our new measurements span $\simeq4$ magnitudes in UV luminosity at $z=9-12.5$, placing new constraints on both the shape and evolution of the LF at early times. We fit our observational data-points with a double-power law (DPL) function and explore the evolution of the DPL parameters. Our UV LF measurements yield a new estimate of the early evolution of cosmic star-formation rate density ($\rho_{\rm{SFR}}$) which confirms the gradual, log-linear decline deduced from early JWST studies, at least out to $z \simeq 12$. Finally we show that the observed early evolution of the galaxy UV LF (and $\rho_{\rm{SFR}}$) can be reproduced in a ${\rm \Lambda}$CDM Universe, with no change in dust properties or star-formation efficiency required out to $z \simeq 12$. Instead, we show that a progressive trend towards younger stellar population ages can reproduce the observations, and we show that the typical ages required at $z \simeq$ 8, 9, 10, and 11 all converge on a time $\simeq 380-330$ Myr after the Big Bang, indicative of a rapid emergence of early galaxies at $z \simeq 12 - 13$. This is consistent with the first indications of a steeper drop-off in the galaxy population we find beyond $z \simeq 13$, possibly reflecting the rapid evolution of the halo mass function at earlier times.