We use a statistical sample of -500 rich clusters taken from 72 deg(2) of the Red-Sequence Cluster Survey (RCS-1) to study the evolution of 630,000 red-sequence galaxies in clusters over the redshift ...range 0.35 < z < 0.95. We construct red-sequence luminosity functions (RSLFs) for a well-defined, homogeneously selected, richness-limited sample. The RSLF at higher redshifts shows a deficit of faint red galaxies (to M(v . -19.7) with their numbers increasing toward the present epoch. This is consistent with the "downsizing" picture in which star formation ended at earlier times for the most massive (luminous) galaxies and more recently for less massive (fainter) galaxies. We observe a richness dependence to the downsizing effect in the sense that, at a given redshift, the drop-off of faint red galaxies is greater for poorer (less massive) clusters, suggesting that star formation ended earlier for galaxies in more massive clusters. The decrease in faint red-sequence galaxies is accompanied by an increase in faint blue galaxies, implying that the process responsible for this evolution of faint galaxies is the termination of star formation, possibly with little or no need for merging. At the bright end, we also see an increase in the number of blue galaxies with increasing redshift, suggesting that termination of star formation in higher mass galaxies may also be an important formation mechanism for higher mass ellipticals. By comparing with a low-redshift Abell cluster sample, we find that the downsizing trend seen within RCS-1 has continued to the local universe.
A primary goal of the upcoming Deep Underground Neutrino Experiment (DUNE) is to measure the (10) MeV neutrinos produced by a Galactic core-collapse supernova if one should occur during the lifetime ...of the experiment. The liquid-argon-based detectors planned for DUNE are expected to be uniquely sensitive to the νe component of the supernova flux, enabling a wide variety of physics and astrophysics measurements. A key requirement for a correct interpretation of these measurements is a good understanding of the energy-dependent total cross section σ(Eν) for charged-current νe absorption on argon. In the context of a simulated extraction of supernova νe spectral parameters from a toy analysis, we investigate the impact of σ(Eν) modeling uncertainties on DUNE's supernova neutrino physics sensitivity for the first time. We find that the currently large theoretical uncertainties on σ(Eν) must be substantially reduced before the νe flux parameters can be extracted reliably: in the absence of external constraints, a measurement of the integrated neutrino luminosity with less than 10\% bias with DUNE requires σ(Eν) to be known to about 5%. The neutrino spectral shape parameters can be known to better than 10% for a 20% uncertainty on the cross-section scale, although they will be sensitive to uncertainties on the shape of σ(Eν). A direct measurement of low-energy νe-argon scattering would be invaluable for improving the theoretical precision to the needed level.
The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will observe several Deep Drilling Fields (DDFs) to a greater depth and with a more rapid cadence than the main survey. In this ...paper, we describe the ``DeepDrill'' survey, which used the Spitzer Space Telescope Infrared Array Camera (IRAC) to observe three of the four currently defined DDFs in two bands, centered on 3.6 \(\mu\)m and 4.5 \(\mu\)m. These observations expand the area which was covered by an earlier set of observations in these three fields by the Spitzer Extragalactic Representative Volume Survey (SERVS). The combined DeepDrill and SERVS data cover the footprints of the LSST DDFs in the Extended Chandra Deep Field-South field (ECDFS), the ELAIS-S1 field (ES1), and the XMM Large-Scale Structure Survey field (XMM-LSS). The observations reach an approximate \(5\sigma\) point-source depth of 2 \(\mu\)Jy (corresponding to an AB magnitude of 23.1; sufficient to detect a 10\(^{11} M_{\odot}\) galaxy out to \(z\approx 5\)) in each of the two bands over a total area of \(\approx 29\,\)deg\(^2\). The dual-band catalogues contain a total of 2.35 million sources. In this paper we describe the observations and data products from the survey, and an overview of the properties of galaxies in the survey. We compare the source counts to predictions from the SHARK semi-analytic model of galaxy formation. We also identify a population of sources with extremely red (3.6\(-\)4.5 \(>1.2\)) colours which we show mostly consists of highly-obscured active galactic nuclei.
We report the discovery of two ultra-faint stellar systems found in early data from the DECam Local Volume Exploration survey (DELVE). The first system, Centaurus I (DELVE J1238-4054), is identified ...as a resolved overdensity of old and metal-poor stars with a heliocentric distance of \({\rm D}_{\odot} = 116.3_{-0.6}^{+0.6}\) kpc, a half-light radius of \(r_h = 2.3_{-0.3}^{+0.4}\) arcmin, an age of \(\tau > 12.85\) Gyr, a metallicity of \(Z = 0.0002_{-0.0002}^{+0.0001}\), and an absolute magnitude of \(M_V = -5.55_{-0.11}^{+0.11}\) mag. This characterization is consistent with the population of ultra-faint satellites, and confirmation of this system would make Centaurus I one of the brightest recently discovered ultra-faint dwarf galaxies. Centaurus I is detected in Gaia DR2 with a clear and distinct proper motion signal, confirming that it is a real association of stars distinct from the Milky Way foreground; this is further supported by the clustering of blue horizontal branch stars near the centroid of the system. The second system, DELVE 1 (DELVE J1630-0058), is identified as a resolved overdensity of stars with a heliocentric distance of \({\rm D}_{\odot} = 19.0_{-0.6}^{+0.5} kpc\), a half-light radius of \(r_h = 0.97_{-0.17}^{+0.24}\) arcmin, an age of \(\tau = 12.5_{-0.7}^{+1.0}\) Gyr, a metallicity of \(Z = 0.0005_{-0.0001}^{+0.0002}\), and an absolute magnitude of \(M_V = -0.2_{-0.6}^{+0.8}\) mag, consistent with the known population of faint halo star clusters. Given the low number of probable member stars at magnitudes accessible with Gaia DR2, a proper motion signal for DELVE 1 is only marginally detected. We compare the spatial position and proper motion of both Centaurus I and DELVE 1 with simulations of the accreted satellite population of the Large Magellanic Cloud (LMC) and find that neither is likely to be associated with the LMC.
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