1211.7058
An HST/WFC3-UVIS view of the starburst in the cool core of the Phoenix cluster
McDonald, ... Reichardt et al
Combination of a high cooling rate and the relatively weak radio source in the cluster core suggests that feedback has been unable to halt runaway cooling in this system, leading to a tremendous burst of star formation.
1211.7059
The vast polar structure of the Milky Way and filamentary accretion of sub-halos
Pawlowski
MW has a vast polar structure (VPOS), a think plane formed by surrounding satellite objects such as dwarf galaxies, globular clusters and streams of disrupted systems, all the way out to 250 kpc from the galaxy center. Orbital directions of satellite galaxies and the preferred alignment of streams with the VPOS demonstrate that the objects orbit within the structure. This strong phase-sapce correlation is at odds with the expectations from simulations of structure formation based on LCDM. Test this scenario using the results of high-res cosmo simulations and found it unable to account for the large degree of correlation of the MW satellite orbits. It is advisable to search for alternative explanations. The formation of tidal dwarf galaxies (TDGs) in the debris expelled from interacting galaxies is a very natural formation scenario of the VPOS. If a number of MW satellites truly are TDGs, mistakenly interpreting them to trace the DM sub-structure of the MW halo would significantly enhance the 'small-scale' problems which are already known to plague the LCDM model.
1211.7062
The observed relation between stellar mass, dust extinction and star formation rate in local galaxies
Zahid, Yates, Kewley, Kudritzki
The relation between dust extinction and SFR changes with stellar mass. For galaxies at the same stellar mass dust extinction is anti-correlated with the SFR at stellar masses <1e10 Msun. There is a sharp transition in the relation at a stellar mass of 1e10 Msun; at larger stellar masses, dust extinction is positively correlated with the SFR for galaxies at the same stellar mass. The observed relation between stellar mass, dust extinction and SFR presented in this study helps to confirm similar trends observed in the relation between stellar mass, metallicity and SFR. The relation reported in this study provides important new constraints on the physical processes governing the chemical evolution of galaxies. The correlation between SFR and dust extinction for galaxies with M*>1e10Msun is shown to extend to the population of quiescent galaxies, suggesting that the physical processes responsible for the observed relation between stellar mass, dust extinction and SFR may be related to the processes leading to the shut down of star formation in galaxies.
1211.7063
Taming astrophysical bias in direct dark matter searches
Pato et al
Find: systematic bias on the DM mass and cross-section determination arising from wrong assumptions for its distribution function [of what?] is of order ~1 sigma. A much larger systematic bias can arise if wrong assumptions are made on the underlying MW mass model. In both cases the bias is substantially mitigated by marginalizing over galactic model parameters. Show: velocity distribution can be reconstructed in an unbiased manner for typical DM parameters. Results highlight both the robustness of the DM mass and cross-section determination using the standard Maxwellian velocity distribution and the importance of accounting for astrophysical uncertainties in a statistically consistent fashion.
1211.7068
The metal aversion of LGRBs
Graham, Fruchter
Conclude: the low-metallicity preference of LGRBs is not primarily driven by the anti-correlation between SF and metallicity, but rather must be overwhelmingly due to the astrophysics of the LGRBs themselves. 3/4 of LGRB sample found at metallicities below 12+log(O/H)<8.6, while less than a 1/10 of local SF is at similarly low metallicities [shouldn't they be comparing this at similar redshifts?]. Able to exclude the possibility that the LGRB host metallicity aversion is caused by the decrease in galaxy metallicity with redshift [Oh.]. The presence of strong metallicity difference between LGRBs and Ic-bI SNe largely eliminates the possibility that the observed LGRB metallicity bias is a byproduct of a difference in the initial mass functions of the galaxy populations. Rather, metallicity below half-solar must be a fundamental component of the evolutionary process that separates LGRBs from the vast majority of Ic-bI SNe and from the bulk or local SF.
1211.7077
Understanding the nature of luminous red galaxies (LRGs): connecting LRGs to central and satellite sub halos
Masaki, Hikage, Takada, Spergel, Sugiyama
A new abundance matching method to construct a mock catalog of LRGs in SDSS, using catalogs of haloes and subhalos in N-body simulations for a Lambda-dominated CDM. Assum that simulated haloes at z=2 (z2-halo) are progenitors for LRG-host subhalos observed today; label the most tightly bound particles in each progenitor z2-halo as LRG "stars". Then identify the subhalos containing these stars to z=0.3 in descending order or masses of z2-halos until the comoving number density of the matched subhalos becomes comparable to the measured number density of SDSS LRGs (n_LRG=1e04 (h/Mpc)^3). The only free parameter is the number density of haloes identified at z=2 and this parameter is fixed to match the observed number density at z=0.3. By tracing subsequent merging and assembly histories of each progenitor z2-halo, directly compute (from N-body sims) the distributions of central and satellite LRGs and their internal motions in each host halo at z=0.3. While SDSS LRGs are galaxies selected by the magnitude and color cuts from SDSS images and are not necessarily a stellar-mass-selected sample, the mock catalog reproduces a host of SDSS measurements: the HOD for central and stellite LRGs, the projected auto-correlation function of LRGs, the cross-correlation of LRGs with shapes of BG galaxies (LRG-galaxy WL), and the non-linear z-space distortion effect, the FoG effect, in the angle-averaged, z-space power spectrum.
1211.7082
Low-mass black holes as the remnants of primordial black hole formation
Greene
The discovery of BHs with intermediate mass is the key to understanding whether SMBH can grow from stellar-mass black holes, or whether a more exotic process accelerated their growth only hundreds of millions of years after the BB. Focus on searches for BHs with masses 1e4-6 Msun that are found at galaxy centers. Review the searches for these BHs to date, and show tentative evidence, from the number of these BHs that are discovered today in small galaxies, that the progenitors of SMBHs were formed as 1e5 to 1e6 Msun BHs via the direct collapse of gas.
1211.7096
Reconstructing three-dimensional parameters of galaxy clusters via multifrequency SZ observations
Morandi, Nagai, Cui
SZ: determine ICM temperature and estimate the cluster mass; future high-res multifrequency SZ observations promise to enable detailed studies of ICM structures, by measuring the ICM temperature through the temperature-dependent relativistic corrections. Develop a non-parametric method to derive 3d physical quantities, including T, P, total M, and peculiar v, of galaxy clusters from SZ observations alone. Test the performance of this method using hydro-sims of galaxy clusters to assess systematic uncertainties in the reconstructed physical parameters. In particular, analyze mock CCAT SZ observations, taking into account various sources of systematic uncertainties associated with instrumental effects and astrophysical FGs. Show that this method enables accurate reconstruction of 3d ICM profiles, while retaining full information about the gas distribution. Discuss application of this technique.
1211.7252
Interstellar C60+
Berne, Mulas, Joblin
Buckminsterfullerene (C60) detected in IR emission in ISM, including in the proximity of massive stars, where physical conditions could favor the formation of the cationic form, C60+. In addition, C60+ was proposed as the carrier of two diffuse interstellar bands in the NIR (firm id depends on gas-phase spectroscopic data). Based on observation, theoretical calculations, and on laboratory studies, 4 bands at 6.4, 7.1, 8.2 and 10.5 microns seen in NGC7023 reflection nebula, attributed to C60+. Detection confirms thatl arge carbon molecules exist in the gas-phase in these environments; in addition, the relative variation of the C60 and C60+ band intensities constitutes a potentially power probe of the physical conditions in highly UV-irradiated regions.
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