1308.4132
How dead are dead galaxies? Mid-infrared fluxes of quiescent galaxies at redshift 0.3 < z < 2.5: implications for star formation rates and dust heating
Fumagalli, ... van Dokkum, ... Kriek, ... Rix, ... et al
Investigate SFRs of quiescent galaxies at 0.3<z<2.5 using 3d-HST WFC3 grism spectroscopy and Spitzer MIR data. Select quiescent galaxies on the basis of the widely used UVJ color-color criteria. SED fitting (rest frame optical and NIR) indicates very low SFRs for quiescent galaxies (sSFR~1e-12/yr). However, SED fitting can miss SF if it is hidden behind high dust obscuration and ionizing radiation is re-emitted in the MIR. It is therefore fundamental to measure the dust-obscured SFRs with a MIR indicator. Stack the MIPS-24um images of quiescent objects in 5 redshift bins centered on z=0.5, 0.9, 1.2, 1.7, 2.2 and perform aperture photometry. Including direct 24um detections, find sSFR~1e-11.9 * (1+z)^4 /yr. These values are higher than those indicated by SED fitting, but at each redshift they are 20-40 times lower than those of typical SF galaxies. The true SFRs of quiescent galaxies might be even lower, as it is shown that the MIR fluxes can be due to processes unrelated to ongoing SF, such as cirrus dust heated by old stellar populations and circumstellar dust. Measurements show that SF quenching is very efficient at every redshift. The measured SFR values are at z>1.5 marginally consistent with the ones expected from gas recycling (assuming that mass loss from evolved stars refuels SF) and well above that at lower redshifts.
1308.4141
21-cm absorption from galaxies at $z\sim0.3$
Gupta et al
As the title says. Two intervening systems towards quasars detected.
1308.4142
The locations of halo formation and the peaks formalism
Hahn, Paranjape
Investigate a fundamental problem of structure formation: predicting the mass function of collapsed, virialized structures from the properties of the Lagrangian density field. In this paper, focus on structure formation from a perturbation spectrum with a small-scale cut-off (as in warm dark matter cosmologies) in which the number of density peaks - and the resulting number of virialized objects - is finite. The PS cut-off results in a strong suppression of low mass objects, providing additional leverage to rigorously test which perturbations collapse and to what mass. Find that all haloes are consistent with forming near peaks of the initial density field. The density of a proto-halo depends strongly on the ellipticity of the Lagrangian velocity shear field, but not on its prolateness. Demonstrate that, while standard excursion set theory with correlated steps completely fails to reproduce the mass function, the inclusion of the peaks constraint leads to the correct number of haloes but significantly underpredicts the masses of low-mass objects (with the halo mass function at low masses behaving like dn/dln m ~ m^2/3). This prediction is very robust and cannot be easily altered within the framework of a single collapse barrier. The nature of collapse in the presence of a small-scale cut-off thus reveals that excursion set calculations require a more detailed understanding of the collapse-time of a general ellipsoidal perturbation in order to predict the ultimate collapsed mass of a peak - a problem that has been hidden in the large abundance of small-scale structure in CDM. Demonstrate how this problem can be resolved within the excursion set framework.
1308.4145
The first analytical expression to estimate photometric redshifts suggested by a machine
Krone-Martins, Ishida, de Souza
A simple and reliable analytic, functional form to determine photo-z of galaxies; derived from 41k galaxies from SDSS DR10 spectroscopic sample. The method automatically dropped the u and z bands, relying only on g,r, and i for the final solution. Apply this expression to the other 1.4M galaxies with z_spec, achieve a mean dz/(1+z_s)<0.0086 and scatter 0.045 wen averaged up to z<1.0. This work is the first use of symbolic regression in cosmology, representing a leap forward in astronomy-data-mining connection.
1308.4150
Damn you, little h! (or, real-world applications of the Hubble constant using observed and simulated data)
Croton
He Hubble constant H0, or its dimensionless equivalent, "littel h", is a fundamental cosmological property that is now known to an accuracy better than a few percent. Despite its osmological nature, little h commonly appears in the measured properties of individual galaxies. This can pose unique challenges for users of such data, particularly with survey data. In this paper, show how little h arises in the measurement of galaxies, how to compare like-properties from different datasets that have assumed different little h cosmologies, and how to fairly compare theoretical data with observed data, where little h can manifest in vastly different ways. This last point is particularly important when observations are used to calibrate galaxy formation models, as calibrating the wrong (or no) little h can lead to disastrous results when the model is later converted to the correct h cosmology. Argue that in this modern age, little h is an anachronism, being one of the least uncertain parameters in astrophysics, and propose that observers and theorists instead treat this uncertainty like any other. Conclude with a "cheat sheet" of nine points that should be followed when dealing with little h in data analysis.
1308.4164
DESI and other dark energy experiments in the era of neutrino mass measurements
Font-Ribera, McDonald, Mostek, Reid, Seo, Slosar
Fisher matrix projections for future cosmological parameter measurements, including neutrino masses, DE, curvature, modified gravity, the inflationary perturbation spectrum, non-Gaussianity, and dark radiation. Focus on DESI and generally redshift surveys (BOSS, HETDEX, eBOSS, Euclid, and WFIRST), but also include CMB (Planck) and WL (DES and LSST) constraints. The goal is to present a consistent set of projections, for concrete experiments, which are otherwise scattered throughout many papers and proposals. Include neutrino mass as a free parameter in most projections, as it will inevitably be relevant -- DESI and other experiments can measure the sum of neutrino masses to ~0.02 eV or better, where the minimum possible sum is ~0.06 eV. Note that the BAO-only use of galaxy clustering is substantially degraded as a DE probe in the presence of neutrino mass uncertainty -- using broadband galaxy power is critical, especially pushing it to as small a scale as possible, and big gains are achieved by combining lensing survey constraints with redshift survey constraints. Do not try to be especially innovative, e.g., in careful treatments of potential systematic errors -- these projections are intended as a straightforward baseline for comparison to more detailed analyses.
1308.4299
Dust properties of clumpy disc galaxies at z~1.3 with Herschel-SPIRE
Wisnioski, Glazebrook, Blake, Swinbank
Present FIR derived dust properties from Herschel SPIRE of the WiggleZ kinematic sample of13 SF galaxies at z~1.3, with existing ancillary ~kpc resolution integral field spectroscopy. Detect 3 galaxies individually and place limits on the remainder by stacking. The detected galaxies, two clumpy disks and one merger, have cold dust temperatures of ~26 K and have IR luminosities of ~1.2e12 Lsun, determined by modified BB fitting. The 2 detected disc galaxies have the largest Ha surface areas of the sample and have the reddest UV to NIR SED. The likely source of the IR luminosity in these objects is dust heated by the interstellar radiation field and young stellar emission from the clumps within the discs. The source of IR luminosity for the merger is likely a dust heated by a starburst resulting from the merger. The WiggleZ detections are among the coldest and lowest luminosity individual objects detected in the FIR at z>1. When combining the kinematic data, find that none of the compact galaxies nor the 'dispersion dominated' galaxies of the WiggleZ kinematic sample are detected, implying that they have warmer dust temperatures. The compact objects show the highest Ha velocity dispersions in the sample, in qualitative agreement with bulge formation models. These FR results strengthen the interpretation that the majority of galaxies in this sample constitute different stages in clumpy disc formation as presented from ancillary kinematic analysis.
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