1201.2404
Photoevaporating Proplyd-like objects in Cygnus OB2
Wright, Drake, Drew, Guarcello, Guthtermuth, Hora, Kraemer
* Proplyd: externally illuminated photo-evaporating protoplanetary disks.
* Cygnus X: wide SF region, one of the most luminous objects in the sky at radio wavelengths.
* Cygnus OB2: home to some of the most massive and most luminous stars known.
Discovery of 10 proplyd-like objects in the vicinity of the massive OB association Cygnus OB2. Clearly resolved in HST/ACS, near-IR and mid-IR images. Exhibit tadpole shape as seen in Orion proplyds: bright ionization front at the head facing the central cluster of massive stars, and a tail stretching in the opposite direction. Also show secondary ionization fronts, complex tail morphologies or multiple heads. They must be either proplyds or 'evaporating gaseous globules' (EGGs) left over from fragmenting molecular cloud, but neither scenario fully explains observations. Typical sizes are 50-100k AU, larger than Orion proplyds, but in agreement with theoretical scaling of proplyd size with distance from ionizing source. Located at projected separations of 6-14pc from the OB association, compare to 0.1pc for the Orion proplyds, but are clearly being photoionized by the 65 O-type stars in Cyg OB2. Central star candidates are identified in near- and mid-IR images, supporting the proplyd scenario, though their large sizes and notable asymmetries is more consistent with the EGG scenario. A 3rd possibility is considered: a unique class of photoevaporating partially-embedded young stellar objects that have survived the destruction of their natal molecular cloud. Has implications of the properties of stars that form in the vicinity of massive stars.
1201.2405
The IRX-beta relation on sub-galactic scales in star-forming galaxies of the Herschel Reference Survey
Boquien et al
Rest-frame UV emission needed to measure cosmic SFR, but UV is dust-reddened. The attenuation and UV color are correlated and can be corrected for, but this relation is different between starburst galaxies and normal SF galaxies. Still not understood why SF galaxies deviate from the UV color-attenuation relation of SB galaxies. Hint: shape of the attenuation curve and age of stellar populations have a role. Use SED fitting code to model the far UV to the far IR emission of a set of 7 reasonably face-on spiral galaxies. Explored the influence of a wide range of physical parameters to quantify their influence and impact on the UV color-attenuation relation. Found: deviation can be best explained by intrinsic UV colour differences between different regions in galaxies. The shape of attenuation curve (its variation) can also play a role. Standard age estimators give poor predictions of the intrinsic UV color. When correcting the emission of normal star-forming galaxies for the attenuation, it is crucial to take into account possible variations in the intrinsic UV colour as well as variations of the shape of the attenuation curve.
1201.2406
How the merger of two white dwarfs depends on their mass ratio: orbital stability and detonations at contact
Dan, Rosswog, Guillochon, Ramirez-Ruiz
WD binary mergers of 0.2 to 1.2 Msun, account for different chemical compositions. Agrees well with mass transfer stability analysis. Find: large fraction of He-accreting binary systems explode. Some fraction of these systems can explode at earlier times via detonations induced by instabilities in the accretion stream, as demonstrated in previous work. Do not find definitive evidence for an explosion in any of the double C-O systems. The available parameter space for a successful detonation in a WD binary of pure C-O composition is small. Wide variety of dynamically unstable systems are viable type Ia candidates.
1201.2407
Constraining satellite galaxy stellar mass loss and predicting intrahalo light I: Framework and results at low redshift
Watson, Berlind, Zentner
New technique to constrain how satellite galaxies lose stellar mass and contribute to the diffuse intrahalo light (IHL). For 2 different models, predict stellar masses of a population of galaxies and use abundance matching to predict the clustering of several r-band luminosity threshold samples from SDSS. Abundance matching assuming no stellar mass loss overestimates the correlation function on small scales (<1Mpc), and vice versa. Model with time delay in stellar mass loss after DM halo mass is lost works better.
1201.2408
The star formation & chemical evolution history of the sculptor dwarf spheroidal galaxy
de Boer, et al
Deep BVI photometry of Sculptor dwarf spheroidal galaxy with spectroscopic metallicity distriubions of RGB stars allows detailed and complete SFH and accurate timescale for chemical enrichment. SFH shows galaxy is dominated by old (>10Gyr), metal-poor stars, but a younger, more metal-rich populations also present. Old population present at all radii, while more metal-rich, younger stars are more centrally concentrated. Find: 7.8e6 Msun was formed between 14 and 7 Gyr ago (peak at 13-14 Gyr). Trends in alpha-elements match what is expected from an extended, relatively uninterrupted period of continuing SF of 6-7 Gyr. SNe enrichment began ~2Gyr after the start of SF in Sculptor.
1201.2409
Dissecting the morphological and spectroscopic properties of galaxies in the local Universe: I. Elliptical galaxies
Agurri et al
Revisit SFH of local ellipticals using novel selection method on SDSS DR7. Show that morphologically defined ellipticals are distributed in 3 classes: (1) bulk (50%) formed by a well-defined class of galaxies with old stellar populations that formed their stars ate very early epochs in a short episode of star formation, dominates scaling relations, represent the canonical elliptical class. (2) at the low mass end, find population of slightly larger ellipticals, with smaller velocity dispersions at fixed stellar mass, which seem to have experienced a more recent episode of star formation probably triggered by gas-rich minor mergers. (3) the high mass end tends to be dominated by a slightly more metal rich and more efficient SF than the reference class, contributes to the curvature of the mass-size relation at high masses.
1201.2413
Integrated optical polarization of nearby galaxies
Jones, Wang, Krisciunas, Freeland
Must galaxies have no significant level of linear polarization (<1%). Fraction of galaxies show a loose correlation between the polarization and position angle of the galaxy, indicating dust scattering is the main source of optical polarization. Unbarred spiral galaxies are consistent with the predicted relationship with inclination from scattering models of ~sin^2i.
1201.2414
Satellites around massive galaxies since z~2
Marmol-Queralto, Trujillo, Perez-Gonzalez, Varela, Barro
1201.2426
Effects of unstable dark matter on large-scale structure and constraints from future surveys
Wang, Zentner
Decaying dark matter (DDM) into less massive, stable dark matter (SDM) with a recoil or "kick" velocity vk can induce free-streaming suppression of matter fluctuations. This suppression may be probed via weak lensing power spectra measured by a number of forthcoming imaging surveys that aim primarily to constrain DE. Using scales on which linear perturbation theory alone is valid (l<300), surveys like Euclid or LSST can be sensitive to vk>90km/s for lifetimes tau=1-5 Gyr. More aggressive constraints: l<3000, vk~10km/s, tau<10Gyr. Lensing will provide a particularly interesting complement to existing constraints in that they will probe the long lifetime regime (tau >> H0^-1) far better than contemporary techniques, if evolution of NL scales well calibrated by numerical sims.
1201.2434
Observational probes of cosmic acceleration
Weinberg, Mortonson, Eisenstein, Hirata, Riess, Rozo
Cosmic acceleration: SNIa, BAO, WL, clusters evidence reviewed. Systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit Stage IV DE facilities such as BigBOSS, LSST, Euclid, and WFIRST. Other approaches : z-space distortions, AP test, Direct measurements of H0. Extensive forecasts for constrains on the DE EoS and parameterized deviations from GR, achievable with Stage III and IV programs that incorporate SNe, BAO, WL and CMB data. Also show level of precision required for other methods to provide constraints competitive with fiducial programs. Emphasize value of a balance program that employs several of the most powerful methods in combinations, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets with broad applications.
1201.2455
Simultaneous constraints on bias, normalization and growth index through power spectrum measurements
Di Porto, Amendola, Branchini
Break degeneracy between galaxy bias, power spectrum normalization, sigma8 and the growth factor from redshift survey without external information, by using a simple and general parameterization for the growth rate (gamma).
1201.2470
A Type Ia SNe at z~1.55 in HST Infrared observations from CANDELS
Rodney, Riess, et al
High-z SNIa observed in CANDELS, more expected.
1201.2558
Dust and gas power-spectrum in M33 (HERM33ES)
Combes et al
Power spectra of de-projected images of late-type galaxies in gas and/or dust emission are powerful diagnostics of the dynamics and stability of their interstellar medium. A shallow power-law at large scales (>500pc), steeper at small scales, break corresponding to LoS thickness of galaxy disk. Present thorough analysis of the power spectra of dust and gas emission at several wavelengths in nearby galaxy M33. Data suggest cool dust likes in a thicker disk than the warm dust, maybe due to SF confined to the plane. Warmer dust more concentrated in clumps. Simulations show that the small-scale power-law reflects the 3d behaviour of the gas layer, steepening strongly while the feedback smoothes the structures by increasing gas turbulence. M33 correspond to a fiducial model with SFR of 0.7 Msun/yr, with 10% SNe energy coupled to gas kinematics.
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