1201.3619
Theoretical estimates of 2pt shear correlation functions using tangled magnetic field power spectrum
Pandey, Sethi
Existence if primordial magnetic fields can induce matter perturbations with additional power at small scales as compared to LCDM, study implication with lensing 2pt correlation function. Imprints left at scales < few arcmin. Compare with CFHTLS, Sub-nG fields might be detected with SNAP.
1201.3621
eLISA: astrophysics and cosmology in the millihertz regime
Amaro-Seoane et al
European New gravitational wave observatory (NGO) mission, dubbed "eLISA" for now. Detect low-frequency gravitational wave band (0.1mHz to 1Hz), with sufficient sensitivity to detect interesting individual astrophysical sources out to z=15 [!]. Coalescence of MBH binaries, mergers of BH during its growth, stellar-mass BHs and compact stars in orbits around MBH, compact WD binaries in Galaxy, binary info in future SNIa, uncertain and unpredicted sources.
1201.3625
Variable gamma-ray sky at 1GeV
Pshirkov, Rubtsov
168 weeks of Fermi-LAT data at E>1GeV. Identify 117 variable sources, 27 of them new. 25 blazar AGNs, another AGN, and a pulsar.
1201.3627
PHL 1811 analogs: a population of x-ray weak quasars
Wu, Brandt, ... Richards, Schneider, ... et al
Radio-quiet PHL 1811 analogs are notably x-ray weak by x13, with hints of heavy x-ray absorption. Correlation with UV emission line properties suggest analogs have extremely wind-dominated broad emission-line regions.
1201.3630
Molecular hydrogen in Lyman alpha emitters
Vallini, Dayal, Ferrara
Estimate H2 content of high-z (z=5.7, 6.6) LAEs from cosmo simulations. H2 mass fraction (f_H2) depends on 3 main LAE physical properties (1) SFR, (2) dust mass, and (3) cold neutral gas mass. f_H2 = 0.5 to 0.9 at z~5.7 of intermediate mass LAEs (decreasing on both ends). Largest value of H2 mass found in the most luminous LAEs. Trend also holds at z~6.6, but lower dust content, so f_H2 is about half of that at z~5.7 (dust contributes to the H2 formation/shielding controlled by dust and intensity of UV Lyman-Werner photo-dissociating radiation produced by stars. Predict CO luminosity, which are consistent with observed upper limits for two z>6 LAEs. Should be detectable with ALMA with sufficient time.
1201.3636
Mass reconstruction using particle based lensing II: quantifying substructure with WL+SL and X-rays
Deb, Morandi, Pedersen, Riemer-Sorensen, Goldberg, Dahle
Mass reconstruction of A1689 using PBL, a method that allows variable resolution depending on data density and S/N; also calculate covariance matrix of mass map. Merging. X-ray has smoother and rounder gas distribution compared to DM. NFW-fitted mass: 1.5e15 Msun (higher than x-ray mass).
1201.3643
Gravitational detection of a low-mass dark satellite at cosmological distance
Vegetti Lagattuta, McKean, Auger, Fassnacht, Koopmans
Early-type lens galaxy at z=0.222 with SL is found to have a (dark) satellite of 2e8 Msun on the Einstein radius, mass similar to Sagittarius galaxy. The source galaxy is at z=0.881. Consistent with predictions from CDM simulations.
1201.3653
On the origin of the high column density turnover in the HI column density distribution
Erkal, Gnedin, Kravtsov
... turnover density depends only weakly on metallicity. Correct for inclination, is insensitive to the resolution of the HI map or to averaging in radial shells. Similarity of HI column density distribution at z=3 and z=0 is due to similarity of the maximum HI surface densities of high-z and low-z disks, presumably a universal process that shape properties of gaseous disks of galaxies. ... Use cosmo sim to explore candidate physical mechanism that can produce a turnover; show that while turbulence within GMCs cannot affect the DLA column density distribution, stellar feedback can affect it significantly if the feedback is sufficiently effective in removing gas from the central 2-3 kpc of high-z galaxies. Meaningful to compare column densities averaged over ~kpc scales estimated from quasar spectra which probe sub-pc scales due to steep power spectrum of HI column density fluctuations in nearby galaxies.
1201.3652
CMB power spectrum parameter degeneracies in the era of precision cosmology
Howlett, Lewis, Hall, Challinor
Planck satellite data: degeneracies in models with flat and non-flat space, non-trivial DE and massive neutrinos. CAMP can differentiate the degeneracies through true physical effects (ISW, CMB lensing, geometrical and other effects through recombination). CMB lensing provides degeneracy-breaking information even without using information in the non-Gaussianity. ...
1201.3659
What triggers star formation in galaxies?
Elmegreen
Young stellar pressures trigger gas accumulation on the periphery of cleared cavities. Stellar pressures also trigger star formation in bright-rim structures, directly squeezing the pre-existing clumps in nearby clouds and clearing out the lower density gas between them. These are observed; but how do they fit into empirical SF laws, which relate the SFR to the gas density? SF follows directly from the formation of cold dense gas (whatever its origin). If average pressure from the weight of the gas layer is large enough to produce a high molecular fraction, then star formation should follow from a variety of processes that combine and lose their distinctive origins. Pressurized triggering might have more influence on the SFR in regions with low average molecular fraction, implying that the arm/interarm ratio of SF efficiency should be higher in the outer regions of galaxies than in the main disks.
1201.3676
Substructure in the most massive GEEC groups: field-like populations in dynamically active groups
Hou, .. et al
... Some galaxy groups contain significant substructure, and these groups have properties and galaxy populations that differ from groups with no detected substructure. These results indicate that the substructure galaxies, which lie preferentially on the group outskirts and could be infalling, do not exhibit signs of environmental effects, since little or no SF quenching is observed in these systems.
1201.3730
Gamma-ray burst host galaxies at low and high redshift
Savaglio
GRB hosts are found to be low-mass, metal poor, blue and SF galaxies. Majority of targets observed are at low z (<2). This implies GRB hosts observed (at low z) must be hosted by small galaxies, since this is where most of the SF is happening today. This seems to be the case (preliminary results). At higher z, unclear; fraction may be associated with dusty regions in massive galaxies.
1201.3761
High-z formation and evolution of central massive objects II: the census of BH seeds
Devecchi, Volonteri, Rossi, Colpi, Zwart
Simulations tracing nuclear star clusters (NCs) and black hole (BH) seeds in a cosmo context. Two mechanisms: (1) Pop III stars in metal free haloes, and (2) runaway stellar collisions in metal poor NCs. Track chemical, radiative and mechanical feedback of stars on the baryonic component of the evolving halos. When and where the the conditions for BH formation met? Trace emergence of BH seeds. BHs already emerge at z~30 as remnants of Pop III stars. Efficiency decreases once feedback become important. At z~15, BHs mostly form in the center of mildly metal enriched haloes inside dense NCs. Birth masses in both channels: 100-1000Msun. Occupation fraction of BHs is a function of both halo mass and mass growth rate [?]. At lower z, the probability of finding a BH shifts toward progressively higher mass halo intervals. At later times, low mass systems rarely form a seed, and already formed BHs are deposited into larger mass systems due to mergers. Model predict that at z=0, haloes above 1e11 Msun should host a BH, most probably inherited during their liftetime. Haloes less than 1e9 Msun have a higher probability to host a native BH, but their occupation fraction decreases below 10%.
1201.3826
An indirect measurement of gas evolution in galaxies at 0.5<z<2.0
Popping, Caputi, Somerville, Trager
High-z galaxy cold gas contents: new method to indirectly determine cold gas surface densities and integrated gas masses from SFR and separate the atomic and molecular gas components. Predicted masses in good agreement with direct measurements quoted in the literature for low and high-z galaxies. Apply to 57k COSMOS galaxies with I<24 mag. Investigate z evolution of galaxy cold and molecular gas content vs stellar mass. Find clear trend between galaxy gas fraction, molecular gas fraction and stellar mass with z, suggesting that massive galaxies consume and/or expel their gas at higher z then less massive objects, and have lower fractions of thir gas in molecular form. Characteristic stellar mass separating gas from stellar dominated galaxies decreases with time. [which way?] Indicates that massive galaxies reach a gas-poor state earlier than less massive objects. These trends can be considered to be another manifestation of downsizeing in SF activity [what is downsizing?].
1201.3876
One step beyond: the excursion set approach with correlated steps
Musso, Sheth
Simple formula that accurately approximates the first crossing distribution of barriers having a wide variety of shapes, by random walks with a wide range of correlations between steps. Special cases of it are useful for estimating halo abundances, evolution and bias, as well as the NL counts in cells distribution. Discuss how it can be extended to allow for the dependence of the barrier on quantities other than overdensity, [like what?] to construct an excursion set model for peaks, and to show why assembly and scale dependent bias are generic even at the linear level.
1201.3889
Pioneer anomaly in pertured FRW metric
Shojaie
Pioneer anomaly is the local evidence for an expanding universe [whoa]. Measures Hubble constant showing expanding behavior of the dynamics of the universe. [i guess he's claiming that the anomaly is due to local FRW expansion? ...oh, he's claiming that the anomaly is similar to the measured H0.]
1201.3899
Identifying luminous AGN in deep surveys: revised IRAC selection criteria
Donley, et al
For deep IRAC data, the AGN selection wedges in use are heavily contaminated by SF galaxies, especially at high z. Use large samples of luminous AGN and high-z SF galaxies in COSMOS, and redevine AGN selection criteria for use in deep IRAC surveys. Both highly complete and reliable, incorporate AGN selection and IR power-law selection while excluding high-z SF galaxies selected via BzK, DRG, LBG and SMG criteria.
1201.3912
Top-heavy IMFs in ultra compact dwarf galaxies?
Dabringhausen, Kroupa
Ultra compact dwarf galaxies (UCDs) are dense stelalr systems at the border between massive star-clusters and small galaxies. The high M/L cannot be explained by stellar populations with canonical stellar initial mass function (IMF), while it is doubtful that non-baryonic DM can accumulate enough on the scales of UCDs for influencing their dynamics significantly. UCDs in the Virgo galaxy cluster apparently also have an over-abundance of NSs, strongly suggesting a top-heavy IMF, which would explain both findings--abundance of stellar remnants.
1201.3369
Triggered star-formation in the inner filament of Centaurus A
Crockett, ... Silk, ... et al
HST observations of the inner filament of Centaurus A, in 3 bands, find a young stellar population near the tip of the filament, age <10Myr (1-4Myr). No further recent SF found along the filament. Based on location and age of this population, and the fact that there is no radio lobe or jet activity near the SF, propose an updated explanation of the origin of the inner filament. 1993 suggestion: radio jet-induced shocks can drive the observed optical line emission. Argue such shocks can naturally arise due to a weak cocoon-driven bow shock (rather than directly from radio jet activity), propagating through the diffuse ISM from a location near the inner northern radio lobe. The shock can overrun a molecular cloud, triggering SF in the dense molecular cores. Ablation and shock heating of diffuse gas then gives rise to the observed optical line and X-ray emission. Deeper X-ray observations should show more diffuse emission along the filament
1201.3370
A data-driven model for spectra: finding double redshift in the SDSS
Tsalmantza, Hogg
Modeling or performing dimensionality reduction on observed spectra or other high-dimensional data with known but non-uniform observational uncertainties. Use iterative inverse-variance-weighted least-squares minimization procedure to generate a best set of basis functions. Method is similar to PCA, but measurement uncertainties used responsibly, and accounts naturally for poorly measured and missing data. [wow.] Models variance in the noise-deconvolved data space. Regularization can be applied in the form of a smoothness prior or a non-negative constraint, without making the method prohibitively slow. Better fit than ordinary PCA basis, because they are optimized (like the likelihood). Apply hypothesis test to compare one-redshift and two-redshift models for spectra, confirming 129 of the 131 lens candidates in sample, and all of the known binary candidates, turns up very few false positives.
* I want to read this
1201.3373
IR an UV SF in BCGs in the ACCEPT sample
Hoffer, Donahue, Hicks, Barthelemy
Many of the BCGs in X-ray clusters with low central gas entropy exhibit enhanced UV (38%) and ind-IR emission (43%), above that expected from an old stellar population. Excesses consistent with on-going SF activity in the BCG, SF that appears to be enabled by the presence of high density, X-ray emitting gas in the core of the cluster of galaxies. Obscured SF occurring in these systems.
1201.3374
On the dust abundance gradients in late-type galaxies: II. Analytical models as evidence for massive interstellar dust growth in SINGS galaxies
Mattsson, Andersen
Simple analytical models of the build-up of dust component and compare these with radial dust distributions observed. Observation: dust gradients are indeed typically steeper than the crresponding metallicity gradients; model indicate very little dust destruction, but significant dust growth in the ISM for most of the galaxies. Conclude: evidence for significant non-stellar dust production, little evidence for dust destruction due to SNe shock waves. Find: dust is reprocessed rather than destroyed by shocks from SNe. Argue that dust abundances derived using standard methods may be overestimated.
1201.3375
On the dust abundance gradients in late-type galaxies: I. effects ofdestruction and growth of dust in the interstellar medium
Mattsson, Andersen, Munkhammar
Theoretical constraints on the effects of destruction by SNe and growth of dust grains in the ISM on the radial distribution of dust in late-type galaxies. The radial gradient of the dust-to-metal ratio is shown to be essentially flat if interstellar dust is not destroyed by SN shock waves, and all dust is produced in stars. If there is net dust destruction by SN shock waves, the gradient is flatter than or equal to the metallicity gradient (assuming gradients have the same sign). If there is a net dust growth in the ISM, then the dust-to-metals gradient is steeper than or equal to the metallicity gradient. Latter result implies that if dust gradients are steeper than metallicity gradients, then it is unlikely dust destruction by SN shock waves is an efficient process, while dust growth must be a significant mechanism for dust production. Conclude that dust-to-metals gradients can be used as a diagnostic for interstellar dust growth in galaxy disk, where a negative slope indicates dust growth.
1201.3400
Red sequence modal colour gradients across intermediate X-ray luminosity galaxy clusters
Jensen, Pimbblet
Investigate red sequence modal galaxy colours with environment, from 45 intermediate x-ray luminosity galaxy clusters from SDSS. Spans a range of Bautz-Morgan types and evolutionary stages, representative of global underlying intermediate L_X cluster sample. Cluster members found, recession velocities and other parameters measured. Construct color magnitude diagrams for each, obtain the position of red sequence, find discordant points due to dust/photometric blending/other causes. Derive M* values in each SDSS passband, combine red sequence of galaxy clusters in a composite sample. Find: model color value of the red sequence varies with radius from the center of this composite cluster and local galaxy density for all SDSS colours; they systematically move blueward with increasing distance from the cluster centers (equivalently lower local galaxy density), while the width of the red sequence increases. Galaxies at the outskirts of these clusters have younger luminosity-weighted ages than those at the core indicating their star formation has been quenced more recently than in the core. These gradients seem to vary with redshift, which would reflect the hierarchical build-up of the red sequence over time.
1201.3447
The diffuse gamma-ray background from SNIa
Lien, Fields
Origin of diffuse extragalactic gamma-ray background (EGB) unsettled. Candidates: unresolved star-forming galaxies, starburst galaxies, blazars. Here: calculate EGB contribution from the interactions of CRs accelerated by SNIa (extends early work which only included core-collapse SNe). For SF galaxies, SNIa makes little difference to the SF EGB prediction, if the CR acceleration efficiencies are the same as in SF galaxies. Updated EGB continues to show that SF galaxies can represent substantial portion of the signal measured by Fermi. For quiescent galaxies, find a wide range of possibilities for the EGB contribution. Dominant uncertainty: mass in hot gas (targets for CRs). EGB estimation very sensitive to the CR acceleration efficiency and confinement, especially in quiescent galaxies. If other sources such s blazars are found to have important contributions to EGB, then either the gas mass or CR content of quiescent galaxies must be significantly lower than in their SF counterparts.
1201.3521
Grain nucleation experiments and other laboratory data
Andersen
Lab measurements of cosmic dust analogues: formation of dust grains influences the stellar atmosphere in 2 ways: in the gas phase chemistry, dust formation results in a depletion of certain elements, influences the molecular composition of the gas and consequently the corresponding opacities. Dust grains have a rather high mass absorption coefficient, which may be comparable to the gas opacity or more. Due to high opacity and resulting radiative pressure, the dust has a strong influence on the structure of atmosphere and wind properties of AGB stars. Great care needed when obtaining lab data, resulting in noticeable consequences for the interpretation of the near IR colors of AGB stars.
1201.3609
Improved constraints on the expansion rate of the universe up to z~1.1 from the spectroscopic evolution of cosmic chronometers
Moresco, Cimatti, Jiminez, ... Stern, Verde, Kneib, Le Fevre, Lilly, et al
Constraints on H(z) in 0.15<z<1.1, from spectroscopic evolution of early-type galaxies as a function of z. 11k galaxies spanning 8 billion years of cosmic lookback time; select the most massive, passively evolving galaxies without signature of ongoing SF. Use these as standard cosmic chronometers, whose differential age evolution as a function of cosmic time directly probes H(z). Analyze the 4000A break as a function of z, use SPS models to theoretically calibrate the dependence of differential age evolution, and estimate Hubble parameter taking into account both statistical and systematic errors. 8 new measurements of H(z), determine change in H(z) to a precision of 5-12% mapping homogeneously the redshift range up to z~1.1...
* I still don't understand how the red galaxies are chronometers.
1201.3614
Gravity and LS non-local bias
Chan, Scoccimarro, Sheth
Relation between galaxy and matter overdensities (bias) is most often assumed to be local. This is unstable under time evolution; provide proofs under several sets of assumptions. In the simplest model, galaxies are created locally and linearly biased at a single time, and subsequently move with the matter (no velocity bias) conserving their comoving number density (no merging). Show that, after this formation time, the bias becomes unavoidable non-local and non-linear at large scales. Identify the non-local gravitationally induced fields in which the galaxy overdensity can be expanded, showing that they can be constructed out of the invariants of the deformation tensor (Galileons). ow that this result persists if include an arbitrary evolution of the comoving number density of tracers .... [whoa, I give up]
The effects of non-local bias seen in the sims are most important for the most biased haloes. The non-locality seen in the simulations is not fully captured by assuming local bias in Lagrangian space. Accounting for these effects when modeling galaxy bias is essential for correctly describing the dependence on triangle shape of the galaxy bispectrum, and hence constraining cosmological parameters and primordial non-Gaussianity. Show that using this formalism removes an important systematic in the determination of bias parameters fomr the gaalxy bispectrum, particularly for lumimous galaxies.
No comments:
Post a Comment