Chien-Hsiu Lee

The old and heavy bulge of M 31 - I. Kinematics and stellar populations

We present new optical long-slit data along 6 position angles of the bulge region of M31. We derive accurate stellar and gas kinematics reaching 5 arcmin from the center, where the disk light contribution is always less than 30%, and out to 8 arcmin along the major axis, where the disk makes 55% of the total light. We show that the velocity dispersions of McElroy (1983) are severely underestimated (by up to 50 km/s). As a consequence, previous dynamical models have underestimated the stellar mass of M31’s bulge by a factor 2. As a further consequence, the light-weighted velocity dispersion of the galaxy grows to 166 km/s and to 170 km/s if also rotation is taken into account, thus reducing the discrepancy between the predicted and measured mass of the black hole at the center of M31 from a factor 3 to a factor 2. The kinematic position angle varies with distance, pointing to triaxiality, but a quantitat ive conclusion can be reached only after simultaneous proper dynamical modeling of the bulge and disk components is performed. We detect gas counterrotation near the bulge minor axis. We measure eight emission-corrected Lick indices. They are approximately constant on circles. Using simple stellar population models we derive the age, metallicity and �-element overabundance profiles. Except for the region in the inner arcsecs of the galaxy, the bulge of M31 is uniformly old (�12 Gyr, with many best-fit ages at the model grid limit of 15 Gyr), slightly �-elements overabundant ([�/Fe]�0.2) and at solar metallicity, in agreement with studies of the resolved stellar components. The predicted u-g, g-r and r-i Sloan color profiles match reasonably well the dust-corrected observ ations, within the known limitations of current simple stellar population models. The stellar populations have approximately radially constant mass(“)

Weak lensing analysis of SZ-selected clusters of galaxies from the SPT and Planck surveys

We present the weak lensing analysis of the Wide-Field Imager SZ Cluster of Galaxy (WISCy) sample, a set of ten clusters of galaxies selected for their Sunyaev-Zel’dovich (SZ) effect. After developing new and improved methods for background selection and determination of geometric lensing scaling factors from absolute multi-band photometry in cluster fields, we compare the weak lensing result with public X-ray and SZ data. We find consistency with published hydrostatic X-ray masses with no significant bias and an intrinsic scatter σint,log10 = 0.13 +0.11 0.13 . We independently calibrate the SPT significance-mass relation and find consistency with previous results at an intrinsic scatter of σint,log10 = 0.09 +0.15 0.09 , with indications for a slightly higher normalisation mass and steeper slope. The comparison of weak lensing mass and Planck Compton parameters, whether extracted self-consistently with a mass-observable relation (MOR) or using X-ray prior information on cluster size, shows significant discrepancies. Since the deviations from the MOR strongly correlate with cluster redshift, we hypothesise that they are related to a size or redshift dependent bias in either signal extraction in the Planck SZ catalogues or their previous X-ray based mass calibration, or in measurement related excess intrinsic scatter.

DETECTION OF AN OUTBURST ONE YEAR PRIOR TO THE EXPLOSION OF SN 2011ht

Using imaging from the Pan-STARRS1 survey, we identify a precursor outburst at 287 and 170 days prior to the reported explosion of the purported Type IIn supernova (SN) 2011ht. In the Pan-STARRS data, a source coincident with SN 2011ht is detected exclusively in the z_(P1) and y_(P1)-bands. An absolute magnitude of M_z ≃ –11.8 suggests that this was an outburst of the progenitor star. Unfiltered, archival Catalina Real Time Transient Survey images also reveal a coincident source from at least 258 to 138 days before the main event. We suggest that the outburst is likely to be an intrinsically red eruption, although we cannot conclusively exclude a series of erratic outbursts which were observed only in the redder bands by chance. This is only the fourth detection of an outburst prior to a claimed SN, and lends credence to the possibility that many more interacting transients have pre-explosion outbursts, which have been missed by current surveys.

Properties of M31: I. Dust. Basic properties and a discussion about age-dependent dust heating

Aims. Observations acquired by the Spitzer Space Telescope and improvements to theoretical modeling of dust emission properties are used to discuss the distribution of dust and its characteristics in the closest neighbor spiral galaxy M31. These data are then used with GALEX FUV, NUV, and SDSS images to study the age dependence of the dust heating process. Methods. Spitzer IRAC/MIPS maps of M31 were matched together and compared to dust emission models allowing us to constrain the dust mass, the intensity of the mean radiation field, the abundance of polycyclic aromatic hydrocarbon (PAH) particles. The total infrared emission (TIR) was analyzed as a function of UV and optical colors and compared to predictions of models that consider age-dependent dust heating. Results. We demonstrate that cold-dust component emission dominates the infrared spectral energy distribution of M31. The mean intensity of the radiation field heating the dust is low (typically

The Pan-STARRS1 Medium-Deep Survey: the role of galaxy group environment in the star formation rate versus stellar mass relation and quiescent fraction out to z ~ 0.8

U M dust ≳ 1.1

Weak lensing analysis of RXC J2248.7−4431

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Kilonova from post-merger ejecta as an optical and near-Infrared counterpart of GW170817

10 7

SILVERRUSH. III. Deep optical and near-infrared spectroscopy for Ly alpha and UV-nebular lines of bright Ly alpha emitters at z=6-7

M_{\odot}

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). II. Discovery of 32 Quasars and Luminous Galaxies at 5.7 < z < 6.8

with a best-fit model value of M dust = 7.6

PROPERTIES OF M31. IV. CANDIDATE LUMINOUS BLUE VARIABLES FROM PANDROMEDA

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