1201.1902
Magnetic Doppler imaging considering atmospheric structure modifications due to local abundances: a luxury or a necessity?
Kochukhov, Wade, Shulyak
* Zeeman-Doppler imaging: tomographic technique dedicated to the cartography of stellar magnetic fields. Uses the ability of magnetic fields to polarize the light emitted (or absorbed) in spectral lines formed in the stellar atmosphere. The periodic modulation of Zeeman signatures during the stellar rotation is employed to make an iterative reconstruction of the vectorial magnetic field at stellar surface. Uses principle of maximum entropy image reconstruction. Stellar magnetism, magnetic geometry, geometry of large arches developed above stellar surfaces. ESPaDOnS at CFHT, NARVAL at Bernard Lyot Telescope.
Magnetic Doppler imaging is currently the most powerful method of interpreting high-resolution spectropolarimetric observations of stars, revealing the presence of unexpected small-scale magnetic fields on the surfaces of Ap stars. Stift+(2012) claim that magnetic inversions are not robust, and are undermined by neglecting a feedback on the Stokes line profiles from the local atmospheric structure in the regions of enhanced metal abundance. Use simulations to refute their claim: prove that published magnetic inversions based on mean stellar atmosphere are robust and reliable, and that the presence of small-scale magnetic field structures on the surfaces of Ap stars is real.
1201.1904
Double-peaked Narrow-line signatures of dual supermassive black holes in galaxy merger simulations
Blecha, Loeb, Narayan
Model the NL region of AGN in hydro sims of galaxy mergers to determine the origin of double-peaked NL (dNL) AGN in merging galaxies and their connection to SMBH pairs, motivated by recent observations. Find dNL AGN induced by the relative motion of SMBH pairs are generic but short-lived feature of gaseous major mergers. dNL AGN are most likely to be observed in late-stage mergers, during the kpc-scale phase of SMBH inspiral or soon after the SMBH merger. Even within the kpc-scale phase, only a minority of dNL AGN are directly induced by SMBH motion; their lifetimes are typically a few Myr. Most double peaks arise from gas kinematics near the SMBH, although prior to the SMBH merger up to 80% of all dNL profiles may be influenced by SMBH motion via altered peak ratios or velocity offsets. The total lifetimes of dNL AGN depend strongly on viewing angle and on properties of the merging galaxies. In a typical merger, at least 10-40% of the double peaks induced by SMBH motion have small projected separations, 0.1-1kpc, such that dual peaks of stellar surface brightness are not easily resolved. dNL profiles with peak velocity splittings >500km/s or with measureable overall velocity shifts are often associated with SMBH pairs. Results support the notion that selection of dNL AGN is a promising method for identifying dual SMBH candidates, but demonstrate the critical importance of high-resolution, multi-wavelength follow-up observations, and the use of multiple lines of evidence, for confirming the dual nature of candidate SMBH pairs.
1201.1906
Unveiling the nature of INTEGRAL objects through optical spectroscopy: IX. 22 more identifications, and a glance into the far hard X-ray universe
Masetti et al
Find that AGNs are the most abundant population among the hard X-ray objects identified through optical spectroscopy. Sometimes high-z AGNs are detected.
1201.1907
What drives the UV colours of passive galaxies?
Smith, Lucey, Carter
Analyse optical and UV colours for passive and optically red Coma cluster galaxies for which there are spectroscopic age and element abundance estimates. FUV-i and FUV-NUV becomes bluer with increasing mass, while u-g and g-i become redder. The UV upturn favours a 'metal-rich single-star' origin. FUV-NUV color show strong correlations with age and Mg/H, but interpretation is not simple because it mixes the effects of the MS turn-off with those from how evolved stars.
1201.1909
New neutrino mass bounds from SDSS III DR8 Photometric luminous galaxies
de Putter, Mena, Giusarma, Ho, Cuesta, Seo, Ross, White, ... Percival, Ross, .. et al
Neutrino mass bounds using 900k luminous galaxies with photoz with 0.45<z<0.65, 10k sq deg (3 Gpc^3/h^3). Sum m_nu<0.26 eV at 95% CL with WMAP7 data and HST hubble parameter. Obtained from 30<l<200 to minimize NL, and a free bias parameter in each of the 4 redshift bins. Study the impact of assuming linear galaxy bias model using mock catalogs, and find a small bias in Omega_DM h^2 (~1-1.5 sigma). In the conservative case, Sum m_nu < 0.36 eV. Study the dependence of the neutrino bound on multipole range (l_max=150 vs l_max = 200) and on which combination the data sets in included as a prior. The addition of SNe and BAO does not significantly improve the neutrino mass bound once the HST prior is included.
1201.1913
Which galaxy property is the best indicator of its host DM halo properties?
Wake, Franx, van Dokkum
Link between galaxy velocity dispersion, mass and other properties (color, morphology) with the properties of DM haloes by comparing the clustering of galaxies at both fixed mass and velocity dispersion. Use SDSS to define a volume limited sample of massive galaxies complete in both stellar mass (>6e10 Msun) and velocity dispersion (>75 km/s). Show at fixed velocity dispersion there is no dependence of the clustering amplitude on stellar or dynamical mass. Conversely, when stellar or dynamical mass are fixed, there is a clear dependence of the clustering amplitude on velocity dispersion with higher dispersion galaxies showing a higher clustering amplitude. WHen stellar or dynamical mass are fixed, there remains a dependence of clustering amplitude on morphology, there is no such dependence when dispersion is fixed. See a dependence of the clustering amplitude on color when both mass and dispersion are fixed. Residual correlation with color is driven by satellite galaxies in massive haloes being redder at fixed dispersion. Lack of similar morphology dependence implies the mechanism turning satellites red is not changing their morphology. Central result: velocity dispersion is more closely related to the clustering amplitude of galaxies than either stellar or dynamical [?? I thought this was velocity dispersion?] mass. Implies that velocity dispersion is more tightly correlated with the halo properties that determine clustering, either halo mass or age, and supports the notion that the SFH of a galaxy is more closely related to its halo properties than its overall mass.
1201.1916
Herschel-ATLAS/GAMA: a census of dust in optically selected galaxies from stacking at sub-mm wavelengths
Borne, Maddox, Dunne,.. et al
Use 80k r-band selected galaxies from GAMA, stack 250, 350, and 500um imaging to gain statistics on the dust emission from galaxies at z<0.35. Find: Low-z galaxies account for 5% of cosmic 250 um BG (4%,3% at 350, 500um, respectively), of which 60% comes from 'blue' and 20% from 'red' galaxies. Compare dust properties of different galaxy populations by dividing the sample into bins of optical luminosity, stellar mass, colour and redshift. In blue galaxies: find dust temperature and luminosity correlate strongly with stellar mass at fixed redshift. In red galaxies: above correlations do not follow, and have overall lower luminosities and temperatures. Make reasonable assumptions to account for flux from lensing [??] by red sequence galaxies, and conclude that galaxies with different optical colours have fundamentally different dust emission properties. Results indicate that while blue galaxies are more luminous [in IR?] than red galaxies due to higher temperature, the dust masses of the two samples are relatively similar. Dust mass is shown to correlate with stellar mass, although the dust/stellar mass ratio is much higher for low stellar mass galaxies, consistent with the lowest mass galaxies having the highest specific star formation rates (sSFRs). Stack 250um/NUV luminosity ratio, finding results consistent with greater obscuration of star formation at lower stellar mass and higher redshift. Sub-mm luminosities and dust masses of all galaxies are shown to evolve strongly with redshift, indicating a fall in the amount of obscured star formation in ordinary galaxies over the last 4 billion years.
1201.1917
NIR and X-ray quasi-periodic oscillations in numerical models of Sgr A*
Dolence, Gammie, Shiokawa, Noble
QPOs result from nonaxisymmetric m=1 structure in the accretion flow excited by MHD turbulence.
* is this observed, though?
1201.1919
Molecular tracers of turbulent shocks in giant molecular clouds
Pon, Johnstone, Kaufman
Giant molecular clouds contain supersonic turbulence and simulations of MHD turbulence show that the supersonic motions decay in roughly a crossing time, which is less than the estimated lifetimes of molecular clouds, which requires a significant release of energy. Run models of C-type shocks propagating into gas with densities around 1e3 /cm^3 at velocities of a few km/s, appropriate for the ambient conditions inside of a molecular cloud, to determine which species and transitions dominate the cooling and radiative energy release associated with sock cooling of turbulent molecular clouds. Find: shocks dissipate their energy primarily through CO rotational transitions, and by compressing pre-existing magnetic fields. ...
1201.1940
The Phoenix project: the dark side of rich galaxy clusters
Gao, Navarro, Frenk, Jenkins, Springel, White
Phoenix project: a set of LCDM simulations of DM component of 9 rich galaxy clusters. Each cluster is simulated at least at two different numerical resolutions. For 8 of them, the highest resolution corresponds to 1.3e8 particles within the virial radius, wihel for one the number is >1e9. Because of the recent assembly, these cluster haloes are significantly less relaxed than galaxy haloes, leading to decreased regularity, increased halo-to-halo variations, and systematic differences in concentration and substructure fraction. All density profiles steepen gradually from the centre outwards, but there is considerable scatter in the dependence of logarithmic slope, gamma, on radius. At the innermost convergence radius, r_conv~3kpc.h (0.2% of virial radius) the mean and rms scatter is gamma=1.05 pm 0.2 for the 9 haloes. For individual clusters, strongly aspherical mass distributions can produce projected surface density variations at given radius spanning up to a factor of 3, depending on projection direction. This may in part explain the high apparent concentration of some observed strong-lensing clusters. The shape of the surface density profile, gamma_p(R) depends only weakly on projection direction, and is quite well approximated in the inner regions by the NFW formula. Substructure in the Phoenix haloes is slightly more abundant, especially in the inner regions, than in the galaxy haloes of the Aquarius Pojrect. The subhalo mass function is also steeper: dN/dM ~ M^-1.98 in the range 1e-6<M_sub/M200<1e-3, compared to M^-1.94 for Aquarius haloes [seems like an insignificant difference to me!]. Resolved subhaloes nevertheless contribute only 11pm3 of the virial mass in the Phoenix clusters [???].
1201.1956
Detection of X-ray galaxy clusters based on the Kolmogorov method
Gurzadyan, Durrent, Ghahramanyan, Kashin, Khachatryan, Poghosian
Analysis of x-ray imaging with Kolmogorov distribution can provide a distinctive signature for galaxy clusters, sensitive to correlations in the cluster x-ray properties and can therefore be used for their identification.
* Kolmogorov distribution: the distribution of the random variable K = sup_{t\in[0,1]}|B(t)|, where B(t) is the Brownian bridge.
* Brownian bridge: continuous-time stochastic process B(t) whose probability distribution is the conditional probability distribution of a Wiener process W(t), a mathematical model of Brownian motion, given the condition that B(0)=B(1)=0. The expected value of the bridge is zero, with variance t(1-t), implying that the most uncertainty is in the middle of the bridge, with zero uncertainty at the nodes.
1201.1960
Moderate Galaxy-galaxy lensing
Mao, Wang, Smith
* Kormendy relation: fundamental plane relation for elliptical galaxies [apparently].
Signatures of moderate lensing include isophotal distortions and systematic shifts in the fundamental plane and Kormendy relation, which can potentially be used to statistically determine the galaxy mass profiles.
1201.2075
Radio properties of H2O maser host galaxies
Zhang, Henkel, Guo, Wang
85 galaxies with reported 22 Ghz H20 maser emission and luminosity distance D>0.5 Mpc studied in 6cm and 20cm radio continuum. 55 targets have both 6 and 20 cm measurements, 42 with masers are related to AGN. Assme power-law dependence; mean value of the resulting spectral index is 0.66. Compare radio properties of the maser galaxies with sample of Seyferts without H2O maser, find (1) spectral indicies agree within the error limits, and (2) maser host galaxies have higher nuclear radio continuum luminosities, exceeding those of the comparison sample by factors of order 5. Considering subsample of galaxies with masers associated with AGN, there seems to be a trend toward rising maser luminosity with nuclear radio luminosity. However, when accounting for the Malmquist effect, the correlation weakens to a level, which is barely significant. Overall, the study indicates that nuclear radio luminosity is a suitable indicator to guide future AGN maser searches and to enhance detection rates, which are low (<10%).
1201.2126
Discovery of black hole spindown in the BATSE catalogue of long GRBs
van Putten
* Maurice!
BATSE catalogue searched for evidence of spindown of BH or proto-NSs bye extracting normalized light curves (nLCs). Find consistency within a few percent of the nLC and the model template for spindown of an initially extremal black hole against high-density matter at the ISCO. The large BATSE size enables a study of the nLC as a function of durations T_90. Attribute spindown against matter at the ISCO [?] to cooling by gravitational-wave emission from non-axisymmetric instabilities in the inner disk or torus as the result of a Hopf bifuracation in response to energetic input from the central black hole. This identification gives an attractive outlook for chirps in quasi-periodic gravitational waves lasting tens of seconds of interest to LIGO, Virgo and the LCGT.
1201.2137
Clustering of SDSSIII Photometric luminous galaxies: the measurement, systematics and cosmological implications
Ho, Cuesta, Seo, de Putter, Ross, White, Padmanabhan, Saito, Schlegel, Schlafly, Seljak, Hernandez-Monteagudo, Sanchez, Percival, Blanton, Skibba, Schneider, Reid, ... et al
Novel treatment of the observational systematics and its applications to the clustering signals from the data set. Measure the angular clustering using an optimal quadratic estimator at 4 redshift slices with an accuracy of ~15% with bin size of delta_l=10 on scales of BAO (l~40-400). Derive cosmological constraints using the full-shape of the power spectra. for flat LCDM with WMAP7 and H0 constraints from HST, find Omega_Lambda=0.73pm0.019 and H0 70.5pm1.6 km/s/Mpc. For an open LCDM model, combined with WMAP7_HST, find Omega_K=0.0035 pm 0.0054 (40% improvement over WMAP+HST alone). With SNe added, find w=-1.071pm0.078, and H) 71.3pm1.7 km/s/Mpc, which is competitive with the latest large scale structure constraints from large spectroscopic surveys such as SDSS DR7 and WiggleZ. The SDSSIII DR8 angular clustering data allows a wide range of investigations into the comological model, cosmic expansion, gaussianity of initial conditions and neutrino masses.
1201.2168
Constraining cluster physics with the shape of x-ray clusters: comparison of local x-ray clusters verses LCDM clusters
Lau, Nagai, Kravtsov, Vikhlinin, Zentner
Simulations of cluster formation have demonstrated that condensation of baryons into central galaxies during cluster formation can drive the shape of the gas distribution in galaxy clusters significantly rounder, even at radii as large as half the virial radius. But such simulations generally predict stellar fractions within cluster virial radii that are 2-3 times larger than the stellar masses deduced from observations. In this work, compare ellipticity profiles of clusters simulated with and without baryonic cooling to the cluster ellipticity profiles derived from Chandra and ROSAT observations in an effort to constrain the fraction of gas that cools and condenses into the central galaxies within clusters. Find that the observed ellipticity profiles are in good agreement with the predictions of non-radiative simulations. On the other hand, the ellipticity profiles of the clusters in simulations that include radiative cooling, SF, and SNe feedback (but no AGN feedback) deviate significantly from the observed ellipticity profiles at all radii. The non-radiative simulations overpredict (underpredict) ellipticity in the inner (outer) regions of galaxy clusters. By comparing the simulations with and without cooling, show that the cooling of gas via cooling flows in the central regions of simulated clusters causes the gas distribution to be more oblate in the central regions, but makes the outer gas distribution more spherical. Find that late-time gas cooling and star formation is responsible for the significantly oblate gas distributions in cluster cores, but the gas shapes outside of cluster cores are set primarily by baryon dissipation at high-z >2.
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