1206.4302
Small-scale hero: massive-star enrichment in the Hercules dwarf spheroidal
Koch, Matteucci, Feltzing
Dwarf spheroidal galaxies are often conjectured to be the sites of the first stars. Check out chemical imprints from enrichment from massive objects are the ultra faint dwarfs (UFDs). Evidence for low heavy element abundances in metal poor Hercules UFD. [that seems to be inconsistent to the theory?] Proceedings.
1206.4303
The stellar population and star formation rates of z~1.5-1.6 [O II] emitting galaxies selected from narrow-band emission-line surveys
Ly, Malkan, Kashikawa, Hayashi, Nagao, Shimasaku, Ota, Ross
SF galaxies at z~1.5, selected by O II emission lines (1300 emitters, z=1.47 and 1.62 with EW>13AA), 2-color id successful (99%). Analyze 1200 with best photometry, can be categorized as BzK (NIR gals) or "BX/BM" (UV) galaxies, and are more complete. Higher OII EW have somewhat bluer continua, have half the stellar mass of galaxies with lower OII EW.
1206.4304
Constrainats on the shapes of galaxy dark matter haloes from weak gravitational lensing
van Uitert, Hoekstra, Schrabback, Gilbank, Gladders, Yee
Study the shapes of galaxy DM haloes by measuring the anisotropy of the WL signal around galaxies in RCS2. Study lens galaxy color dependence, environmental dependence. Find: satellite preferentially reside near the major axis of the lenses. [why is all != <blue + red>?] For an elliptical NFW profile, the ratio of e_h/e_g=1.5 (so the halo ellipticity is larger). For isolated galaxies of 'all' sample, the average shear anisotropy increases to 0.51 pm 0.25 [what is this?] and e_h/e_g = 4.7, while for clustered galaxies the signal is consistent with zero [???].
1206.4305
Precision Near infrared photometry for exoplanet transit observations - I : ensemble spot photometry for an all-sky survey
Clanton et al
NIR observation for detection of exoplanets using the transit technique. Lab experiment on Teledyne Hawaii-2RG detector to emulate an dialyzed star-field.
1206.4306
Star-galaxy classification in multi-band optical imaging
Fadely, Hogg, Willman
Photometric classification techniques on stars and galaxies with intrinsic FWHM < 0.2 arc sec. Consider SED template fitting (unsupervised) and data-driven Support Vector Machines (supervised). Testing with COSMOS ugriz data. No algorithm delivers perfect performance. Conclude that a well trained SVM will outperform template-fitting methods, but a normally trained SVM performs worse. Conclude hierarchical Bayesian template fitting may prove to be the optimal method for source classification in future surveys.
1206.4307
Parsec-scale dust emission from the polar region in the type 2 nucleus of NGC 424
Hoenig, Kishimoto, et al
Study the circumnuclear dust distribution of AGN ("dust torus"). Observe, conclude that majority of pc-scale MIR emission in this type 2 AGN originates from optically thin dust in the polar region of the AGN. Suggest that a readiatively-driven dusty wind (launched in a puffed-up region of the inner hot part of the torus) is responsible for the polar dust. The torus dominates the NIR emission to 5um, while the polar dust is main contributor of MIR flux.
1206.4310
The SWELLS survey - V. A Salperter stellar initial mass function in the bulges of massive spiral galaxies
Dutton et al
Investigation variations of the IMF within individual galaxies, use SL and gas kinematics to measure the normalization of the IMF of the bulge and disk components of 5 massive spiral galaxies. Find bulge mass data consistent with SPS color fits by assuming Salpeter-like normalization of the IMF. Disk masses are less well constrained due to degeneracies with the DM halo, but are consistent with MW type IMFs in agreement with previous studies. Disks sub maximal and baryon dominated at 2.2 disk scale lengths. Provide evidence for non-universal IMF within different components of spiral galaxies.
1206.4311
The stellar initial mass function in red-sequence galaxies: 1-micron spectroscopy of Coma Cluster galaxies with Subaru/FMOS
Smith, Lucey, Carter
Investigate possible variations in the IMF in red-sequence galaxies; obtain 92 red galaxy spectra in Coma cluster. Derive composite spectra in 9600-10500 A range for galaxies grouped according to their velocity dispersion of Mg/Fe ratio. Measure FeH and CaI line (strong in cool dwarf stars, reflect the form of IMF at low mass <0.5 Msun). Compare measured indices against predictions from SPS models matched to the element abundances estimated from optical data. Best reproduced by models with Salpeter IMF. No clear evidence for an increase in dwarf-star content with velocity dispersion. IMF depends on the mode of star formation, with intense rapid-star bursts generating a larger population of low-mass stars.
1206.4314
On the structure of hot gas in halos: Implications for the Lx-Tx relation & missing baryons
Sharma, McCourt, Parrish, Quataert
1d models of hot gas in DM haloes (predict existence of cool cores and explain their structure). Filaments of cold (1e4 K) gas condense out of the ICM in hydrostatic and thermal equilibrium when the ratio of the thermal instability timescale to the free-fall time scale falls below 5-10; corresponds to an upper limit on the density of the ICM and motivates a model in which a density core form wherever the ratio is < 10. Predicts larger and more tenuous cores for lower-mass haloes. For halo masses < 1e13 Msun, the core size approaches the virial radius. Most of the baryons in such haloes cannot be in the hot ICM, but either in the form of stars or in the form of hot gas beyond the virial radius. Because the smaller mass in the ICM and much larger mass available for star formation, the majority of the baryons in low mass haloes (<1e13 Msun) can be expelled beyond the virial radius due to SNe feedback. This can account for the baryons 'missing' from low mass haloes, such as the Galactic halo.
1206.4315
Light bosons and photospheric solutions to the solar abundance problem
Vincent, Scott, Trampedach
Current spectroscopic determinations of the chemical composition of the Sun are starkly at odds with the metallicity implied by helioseismology. Propose: discrepancy may be due to conversion of photons to a new light boson in the solar photosphere [wtf?]
1206.4317
The nonlinear matter and velocity power spectra in f(R) gravity
Li et al
Study the matter and velocity divergence power spectra in a f(R) gravity theory and their time evolution measured from several large-volume N-body simulations with varying box sizes and resolution.
1206.4318
Galaxies behind the Galactic plane: first results and perspectives from the VVV survey
Amores et al
Vista Variables in the Via Lactea (VVV): ESO variability survey in NIR bands (ZYJHKs) toward the Galactic bulge and part of the disk 3 mag deeper than 2MASS. Searched for BG galaxies near the galactic plane using photometry (1.6 sq deg). Find 204 new galaxies candidates from color, size and visual inspection, 10x more than previously known.
1206.4322
The morphologies of massive galaxies at 1<z<3 in the CANDELS-UDS field: compact bulges, and the rise and fall of massive disks
Bruce et al
Study the morphological properties of the most massive galaxies at high z from HST images of 200 galaxies with 1<z_phot<3 and M*>1e11 Msun. Fit to single Sersic or bulge+disk, 90% show good fit. Indicate that these massive galaxies lie both on and below the local size-mass relation, with median R_e~2.6 kpc, a factor of 2.3 smaller than comparably massive local galaxies. Find: bulge-dominated objects in particular show evidence for a growing bimodality in the size-mass relation with increasing z, and by z>2 the compact bulges display effective radii 4x smaller than local ellipticals of comparable mass. Trend appear to extend to the bulge components of disk-dominated galaxies, and vice versa [what vice versa?]. Also find: at 1<z<2 massive galaxies are predominantly mixed bulge+disk systems, and by z>2 they are mostly disk-dominated (at low z, massive galaxies are elliptical dominated). Majority of the disk-domianted galaxies are actively forming stars, but this is also true for many of the bulge-dominated systems. Significant fraction (25-40%) of the most quiescent galaxies have disk-dominated morphologies. Results show that the massive galaxy population is undergoing dramatic changes at this epoch, but they also suggest that the physical mechanisms which quench SF activity are not simply connected to those responsible for the morphological transformation of massive galaxies into present-day giant ellipticals.
1206.4382
A systematic review of strong gravitational lens modeling software
Lefore, Futamase, Akhlaghi
First systematic review of SL modeling software.
1206.4396
A possible signature of primordial stellar populations in $z=3$ Lyman $\alpha$ emitters
Inoue
Examine stellar population which simultaneously accounts for the strength of the LyC and spectral slope of non-ionizing ultraviolet of the LAEs. Stellar populations with metallicity Z>1/50 Zsun can explain the observed LyC strength only with a very top-heavy initial mass function. ...
1206.4437
Prospects for weak lensing studies with new radio telescopes
Brown
Proceedings. Prospects for performing WL studies with new generation of radio telescopes: use polarization observations in radio WL analysis, which can remove contamination signal from intrinsic alignments [how??]. SKA is promising due to its high reolusion, large are surveys which it will perform. Near term: e-MERLIN in UK offers high sensitivity and sub-arcsec resolution required to prove WL techniques in the radio band. Describe the SuperCLASS survey.
1206.4454
The characterization of the distant blazar GB6 J1239+0443 from flaring and low activity periods
Paciani et al
Use SDSS optical data and UV GALEX observations to estimate the thermal-disk emission contribution. This source went through (optical) flux enhancement by 15-30x in the past 6 years, and 10x in 6 months. Flare-up = transition from accretion-disk dominated to synchrotron-jet dominated? Estimate mass of the central BH using the width of the CIV emission line. Analysis of the gamma-ray data taken during flaring episodes indicates a flat gamma-ray spectrum with an extension of up to 15 GeV, with no statistically-relevant sign of absorption from the broad line region, suggesting that the blazar-zone is located beyond the broad line region [??]. Result confirmed by modeling the broad-band SED of the flaring activity periods, and by the accretion disk luminosity and BH mass estimated from archival data.
1206.4479
A hydrodynamical approach to CMB mu-distortions
Pajer, Zaldarriaga
Spectral distortion of CMB can probe primordial perturbations on very small scales by performing large-scale measurements. Discuss all relevant physical phenomena involved in the production and evolution of he mu-type spectral distortion. Main results agree with previous estimates. Also discuss several subleading corrections such as adiabatic cooling and the effects of bulk viscosity, baryon leading and photon heat conduction. Calculae the transfer function for mu-distortions between the end of the mu-era and now.
1206.4486
Broad band photometric reverberation mapping of NGC 4495
Edri, Rafter, Chelouche, Kaspi, Behar
RM to measure the radius of the broad line region and BH mass in the nearby, low luminosity AGN. 9 consecutive night observation, 3 light curves each, over 250 data points in SDSS gri bands. g and r contain time variable contributions from Hbeta and Halpha plus continuum, i band is free of broad lines and is exclusively continuum. Look for correlations for all combinations of filters, and get a reliable estimate of the time lag necessary to compute M_BH. Lag = 3.6 pm 0.8 hours, giving M_BH = (4.9pm2.6)e4 Msun.
1005.1926
Polarization as an indicator of intrinsic alignment in radio weak lensing
Brown, Battye
Polarization orientation angle unaffected by lensing. Polarization coupled with galaxy morphology orientation. Combine these two, and you can infer the original shape position angle, relative to the lensed image. This gets rid of intrinsic alignment effects.
1206.4493
Running a distributed virtual observatory: US Virtual Astronomical Observatory operations
McGlynn, Hanisch, Berriman, Thakar
Intimidating data volumes and rapid technological change, lack of direct control of the underlying and scattered data resources, and the distributed nature of the observatory itself. Discuss how the VAO has addressed these challenges. Facilitation of heterogeneous datasets is a fundamental reason for the virtual observatory. Key aspect of approach: continuous monitoring and validation of VAO and VO services and the datasets provided by the community, monitoring of user requests to optimize access, caching for large datasets, and providing distributed storage services that allow user to collect results near large data repositories. Distributed nature of the VAO requires careful attention to what can be a straightforward operation at a conventional observatory (web site organization/collection and combined analysis of logs).
1206.4536
Two modified ILC methods to detect point sources in cosmic microwave background maps
Vio, Andreani, Ramos, da Silva
Two modifications of the "internal linear combination" method (used to separate the various components that contribute to the CMB. Main advantage of this approach (esp. in handling multi-frequency maps of the same region) is that it doesn't require the 'a priori' knowledge of the spatial power-spectrum of either the CMB and /or the Galactic foreground, and hence more robust and more intuitive to use. [What does it do, though? no description in the abstract.]
1206.4550
Submillimeter observations of millimeter bright galaxies discovered by the South Pole Telescope
Greve et al
Present 11 representative samples of the rare, extremely bright (1.4mm > 15mJy), dust-dominated millimeter-selected galaxies discovered by SPT. All detected with LABOCA (870 um) with 40-130 mJy, approximately and order of magnitude higher than the canonical SMG population. Model SED using simple modified black body and perform the same analysis on samples of SMGs of known redshift (these calibration samples inform the distribution of dust temperature for similar SMG populations, and dust temperature then allows derivation of photo-z and FIR luminosity of the sources). Find median redshift of <z>=3, higher than the <z>=2.2 inferred for the normal SMG population. Apparent size larger tan unlensed calibration sample: these sources are probably gravitationally magnified.
1206.4569
Multilevel Bayesian framework for modeling the production, propagation and detection of ultra-high energy cosmic rays
Soiaporn, Chernoff, Loredo, Ruppert, Wasserman
Sources of UHECRs are unknown but are likely nearby galaxies. Develop Bayesian framework to assess association of UHECRs and candidate sources. Need for more complex models; MCMC methods to implement the approach to model data on 69 UHECRs observed, using 17 nearby AGN as candidate sources. No significant evidence for association of UHECRs with nearby AGNs versus an isotropic population of sources. If the association model is adopted, the fraction of UHECRs associated with these AGN is likely nonzero but well below 50%. Relatively small B-field deflections favored; models that assign a large fraction of UHECRs to a single nearby sources are ruled out unless very large deflections are specified a priori. Including Period 1 data alters the conclusions significantly (it had a E threshold applied), and simulation suggest Period 1 data are anomalous, presumably due to tuning. Accurate and optimal analysis of future data will likely require more complete disclosure of the data.
[Thu **/41] Jun 21
No comments:
Post a Comment