1510.02471
Accretion-induced variability links young stellar objects, white dwarfs, and black holes
Scaringi, et al
The central engines of disc-accreting stellar-mass black holes appear to be scaled down versions of the supermassive black holes that power active galactic nuclei. However, if the physics of accretion is universal, it should also be possible to extend this scaling to other types of accreting systems, irrespective of accretion mass, size or type. Examine new observations, obtained with Kepler/K2 and ULTRACAM, regarding accreting WDs and young stellar objects (YSOs). Every object in the sample displays the same linear correlation between the brightness of the source and its amplitude of variability (mrs-flux relation) and obeys the same quantitative scaling relation as stellar-mass BHs and AGN. Also show that the most important parameter in this scaling relation is the physical size of the accreting objects. This establishes the universality of accretion physics from protostars still in the star-forming process to the SMBHs at the centers of galaxies.
1510.02475
Unveiling a rich system of faint dwarf galaxies in the Next Generation Fornax Survey
Munoz, et al
Report the discovery of 158 previously undetected dwarf galaxies in the Fornax cluster central regions using a deep coadded u, g, and i-band image obtained with the DECam wide-field camera mounted o the 4-m Blanco telescope at CTIO as part of the NGFS. The new dwarf galaxies have quasi-exponential light profiles, effective radii 0.1<re<2.8 kpc and average effective surface brightness values 22.0<mu_i<28.0 mag arcs^-2. Confirm the existence of ultra-diffuse galaxies (UDGs) in the Fornax core regions that resemble counterparts recently discovered in the Virgo and Coma galaxy clusters. Also find extremely low surface brightness NGFS dwarfs, which are several magnitudes fainter than the classical UDGs. The faintest dwarf candidate in the NGFS sample has an absolute magnitude of M_i=-8.0mag. The nucleation fraction of the NGFS dwarf galaxy sample appears to decrease as a function of their total luminosity, reaching from a nucleation fraction of >75% at luminosities brighter than M_i~-15.0 mag to 0% at luminosities fainter than M_i~-10.0 mag. The 2PCF analysis of the NGFS dwarf sample shows an excess on length scales below ~100 kpc, pointing to the clustering of dwarf galaxies in the Fornax cluster core.
1510.02617
Intrinsic alignment contamination to CMB lensing-galaxy weak lensing correlations from tidal torquing
Larsen, Challinor
Correlations of galaxy ellipticities with large-scale structure, due to galactic tidal interactions, provide a potentially significant contaminant to measurements of cosmic shear. However, these intrinsics alignments are still poorly understood for galaxies at the redshifts typically used in cosmic shear analyses. For spiral galaxies, it is thought that tidal torquing is significant in determining alignments resulting in zero correlation between the intrinsic ellipticity and the gravitational potential in linear theory. Here, calculate the leading-order correction to this result in the tidal-torque model from non-linear evolution, using second-order perturbation theory, and relate this to the contamination from intrinsic alignments to the recently-measured cross-correlation between galaxy ellipticities and the CMB lensing potential. Find that the angular cross-correlation from tidal torquing has a very similar scale dependence as in the linear alignment model (believed to be appropriate for elliptical galaxies), but the opposite sign and so increases the observable correlation between CMB lensing and spiral galaxies. The amplitude of the cross-correlation is predicted to depend strongly on the formation redshift, being smaller for galaxies that formed at higher redshift when the bispectrum of the gravitational potential was smaller. Finally, make simple forecasts for constrains on IAs from the correlation of forthcoming cosmic shear measurements with current CMB lensing measurements.
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