1204.1969
On the nature of the Herbig B[e] star binary system V921 Scorpii: geometry and kinematics of the circumprimary disk on sub-AU scales
Kraus, Calvet, Hartmann, Hofmann, Kreplin, Monnier, Weigelt
* B[e] phenomenon (from Miroshnichenko 2007, ApJ): simultaneous presence of low-excitation forbidden line emission and strong IR excess in the spectra of early-type stars. Discovered 30 years ago in our Galaxy. Phenomenon associated with objects at different evolutionary stages, ranging from pre-main-sequence to the planetary nebula stage. New classification proposed for stars with B[e] phenomenon based on the time of dust formation in their environments. Propose that some of the unclassified objects are binary systems that are currently undergoing or have recently undergone a phase of rapid mass exchange, associated with a strong mass loss and dust formation.
Close binary system showing B[e] phenomenon: system surrounded by an enigmatic bipolar nebula, which may have been shaped by episodic mass-loss events, possibly triggered by dynamical interactions between the companion and the circumprimary disk. Investigate the spatial structure and kinematics of the circumprimary disk, with the aim to obtain new insights into the still strongly debated evolutionary stage. Spectro-astrometry and spectro-interferometry [what are these?] used. Br-gamma line emitting gas rotates in the same plane as the dust disk. Use Kepleriran-rotating disk, derive mass of central star at 5.4 Msun(d/1150pc), which is lower than spectra-implied value; object could actually be further away (~2kpc).
1204.1970
Parsec-scale radio emission from the low-luminosity active galactic nucleus in the dwarf starburst galaxy Henize 2-10
Reines, Deller
SMBH of 1e6Msun in the center, a growing BH in a nearby galaxy (smallest SMBH study). Single compact radio source at the putative (low luminosity) AGN. Compact radio emission (<3pc x 1pc), non-thermal brightness (T_B > 3e5K). Emission originates from a single object and excludes possibility of multiple SNe remnants as radio emission origin. A weaker, more extended, off-nuclear source also detected with the LBA; comparison with multi-wavelength ancillary data indicate that the off-nuclear source is co-spatial with a super star cluster (unlike the nuclear core), lacks a detectable X-ray point-source counterpart, and is almost certainly due to a SNe remnant in the host star cluster.
1204.1974
The Swift/UVOT catalogue of NGC4321 star forming sources: a case against density wave theory
Ferraras, Cropper, Kawata, Page, Hoversten
Study the SF regions with high spatial resolution (2.5") in UV, along with optical and IR, Ha to obtain 787 SF region catalog out to 3xR[disc scale], correlate its relationship with the spiral arms. Ha luminosities of the sources have a strong decreasing radial trend, suggesting more massive star forming regions in the central part of the galaxy. Blue sources have a significant excess of flux in the IR at 8 um, revealing the contribution from PAHs, although the overall reddening of these sources stays below E(B-V)=0.2mag. The distribution of distances to the spiral arms is compared for subsamples selected according to Ha luminosity, NUV-optical color, or ages derived from SPS model. Offset expected between these subsamples as a function of radius if the patter speed of the spiral arm were constant (as predicted by classical density wave theory). No significant offsets found, favoring instead a mechanism where the patter speed has a radial dependence.
1204.1977
The 4Ms Chandra deep field-south number counts apportioned by source class: pervasive active galactic nuclei and the ascent of normal galaxies
Lehmer et al
Cumulative and differential number counts measurements in CDF-S survey, in 0.5-2 keV, 2-8 keV, 4-8 keV, and 0.5-8 keV. Apply Bayesian, allows reliable calculation of number counts down to flux limits that are factors of 1.9-4.3 times fainter than the previous studies. In the soft band (the most sensitive), the maximum source density reaches 27800/sqdeg. Combine with multi wavelength data, count by source populations (AGN, normal galaxies, galactic stars) and subpopulations (function of z, AGN absorption, luminosity, galaxy morphology), and test models that describe their evolution. Find that AGNs still dominated the X-ray number coins down to the faintest flux levels for all bands (14900/sqdeg). Find normal galaxy counts rise rapidly near the flux limits (12700/sqdeg) and make up 46% of the total number counts. The rapid rise of the galaxy counts toward faint fluxes, and significant normal-galaxy contributions to the overall number counts indicate that normal galaxies will overtake AGNs just below the soft-band flux limit at 4Ms and will provide a numerically significant new X-ray source population in future surveys that reach below current sensitivity; many of new X-ray sources should be cosmological distant (z>0.6) normal galaxies.
1204.1978
Cosmic dust in MgII absorbers
Menard, Fukugita
MgII absorbers induce reddening on background quasars. Measure this effect and infer the cosmic density of dust residing in these systems to be Omega~2e-6, comparable to the amount of dust found in galactic disks or about half the amount inferred to exist outside galaxies. Also estimate neutral hydrogen abundance in MgII clouds to be Omega~1.5e-4, which is approximately 5% of hydrogen in stars in galaxies. Implies a dust-to-gas mass ratio for MgII clouds of about 1/100, which is similar to the value for normal galaxies. This would support the hypothesis of the outflow origin of MgII clouds, which are intrinsically devoid of stars and hence have no sources of dust. Considerations of the dust abundance imply that the presence of MgII absorbers around galaxies lasts effectively for a few Gyr. High-z absorbers allow us to measure the rest-frame extinction curve to 900 Angstroms at which the absorption by the Lyman edge dominates over scattering by dust in the extinction opacity.
1204.2014
Star hoppers: planet instability and capture in evolving binary systems
Kratter, Perets
Binary stellar evolution can influence dynamical evolution of planets. Stellar evolution can trigger dynamical instabilities that drive planets into chaotic orbits. This instability leads to planet-star collisions, exchange of the planet between the binary stars ("star-hoppers"), and ejection of the planet from the system. Because planets often suffer close encounters with the primary on the asymptotic giant branch, captures during a collision with the stellar envelope are also possible. Such capture could populate the habitable zone around white dwarfs.
1204.2020
The infrared properties of sources matched in the WISE all-sky and Herschel-ATLAS surveys
Bond, et al
IR properties of sources detected over GAMA (36 sqdeg) 15-hr equatorial field, from Herschel-ATLAS and WISE. Can identify 50% of H-ATLAS sources in WISE, 630/sqdeg surface density. ~2/3 of these sources have measured spectroscopic or optical/near-IR photometric redshifts of z<1. For sources at z<0.3, find linear correlation between IR luminosity at 3.4 um and 250 um, with 50% scatter over 1.5 orders of magnitude in luminosity (1e9~10.5 Lsun). By contrast, the matched sources w/o previously measured redshifts (r>20.5) have 250-350 um flux density ratios that suggest either high-redshift galaxies (z>1.5) or optically faint low-z galaxies with unusually low temperatures ("T<20" [wtf?]). Their small 3.4-250 um flux ratios favor a high-z galaxy population, as only the most actively star-forming galaxies at low redshift exhibit comparable flux density ratios. Furthermore, find a relatively large AGN fraction (30%) in a 12 um flux-limited subsample of H-ATLAS sources, also consistent with there being a significant population of high-z sources in the no-redshift sample.
1204.2056
New constraints on primordial black holes abundance from femtolensing of gamma-ray bursts
Barnacka, Glicenstein, Moderski
Abundance of primordial black holes currently significantly constrained in a wide range of masses; weakest limits established for the small mass objects, where the small intensity of the associated physical phenomenon provides a challenge for current experiments. Use gamma-ray bursts with known redshifts detected by the Fermi GRB monitor to search for the femtolensing effects caused by compact objects. Lack of Femtolensing detection in the GBM data provides new evidence that primordial BHs in the mass range 5e17-20g do not constitute a major fraction of DM.
1024.2082
Momentum-driven feedback and the mass-sigma relation in non-isothermal galaxies
McQuillin, McLaughlin
Solve for velocity fields of momentum-conserving supershells driven by steady winds from SMBHs or nuclear star clusters (Central massive objects: CMOs). Look for critical CMO mass that allows such a shell to escape from its host galaxy. If host galaxy DM == SIS, find that CMO mass which scales with the halo velocity dispersion as M_crit prop sigma^4, is necessary (but not sufficient) to drive shells to large radii in the halo. Furthermore, a CMO mass at least 3 times the value is required to drive the shell to escape speed of the halo. For CMOs embedded in protogalaxies with non-isothermal DM haloes, find a critical CMO that is sufficient to drive any shell under a steady wind to escape any galaxy with a peaked circular speed profile. In the limit of large halo mass (relevant to real galaxies), this critical CMO mass depends only on the value of the peak circular speed of the halo, scaling as M_crit propto V_c,pk^4. Results therefore relate to observational scalings between black hole mass and asymptotic circular speed in galaxy spheroids. They also suggest a natural way of extending analysis of M-sigma relations for BHs in massive bulges, to include similar relations for nuclear clusters in lower-mass and disc galaxies.
1204.2103
Observing gravitational lensing effects by Sgr A* with GRAVITY
Bozza, Mancini
Light from clusters of stars orbiting Sgr A* is gravitationally lensed, resulting in astrometric displacement of the primary image, the creation of a secondary image that may shift the centroid of Sgr A*, magnification effects on both images. The soon-to-come 2nd generation VLTI instrument GRAVITY can observe in IR the galactic center at high [what?] resolution, opening the possibility to observe such effects. Investigate the observability limits for GRAVITY of gravitational lensing effects on the S-stars in the parameter space. The easiest effect to be observed in the next years is the astrometric displacement of primary images; the shift of star S17 from Keplerian orbit will be detected as soon as GRAVITY becomes operative. Possible to detect effects related to the spin of BH, or post-Newtonian orders in the deflection.
1204.2229
Constraining primordial non-Gaussianity with cosmological weak lensing: shear and flexion
Fedeli, Bartelmann, Moscardini
Examine the cosmological constraining poet of future large-scale WL surveys on the model of Euclid, with particle reference to primordial non-Gaussianity. Estimators of projected matter power spectrum based on both shear and flexion. Delta fNL~100 from WL bispectrum (local); worse for equilateral and orthogonal. Competitiveness of flexion depends on noise in it, but in the worst case, flexion doesn't add much; it only matters at small scales where flexion noise decreases (l_max=20,000). In moderate flexion noise, flexion constraining a factor of x2 better than that of shear, bounds on sigma8 and fNL improved by a factor of ~3 upon combination.
1204.2232
Galaxy-galaxy(-galaxy) lensing as a sensitive probe of galaxy evolution
Saghiha, Hilbert, Schneider, Simon
Consider 2 SAM based on Millennium (N-body sim), Durham vs Garching. Generate mock lensing observations of the two models, employ FFT to compute 2nd and 3rd order aperture statistics in the simulated fields for various galaxy samples. Find both models predict qualitatively similar aperture signals, but large quantitative differences (Durham model predicts larger amplitudes in general). In both, red galaxies exhibit stronger aperture signals than blue galaxies. Using these and assuming a linear deterministic bias model, measure relative bias ratios of red and blue galaxy samples. Find that a linear deterministic bias is insufficient to describe the relative clustering of model galaxies below ten arcmin angular scales. Dividing galaxies into luminosity bins, the aperture signals decrease with decreasing luminosity for brighter galaxies, but increase again for fainter galaxies. This increase is likely an artifact due to too many faint satellite galaxies in massive group and cluster haloes predicted by the models. Our study shows that g-g-g lensing is a sensitive probe of galaxy evolution.
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