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Register a new userTesting for a large local void by investigating the Near-Infrared Galaxy Luminosity Function
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Recent cosmological modeling efforts have shown that a local underdensity on scales of a few hundred Mpc (out to z ~ 0.1), could produce the apparent acceleration of the expansion of the universe observed via type Ia supernovae. Several studies of galaxy counts in the near-infrared (NIR) have found that the local universe appears under-dense by ~25-50% compared with regions a few hundred Mpc distant. Galaxy counts at low redshifts sample primarily L ~ L* galaxies. Thus, if the local universe is under-dense, then the normalization of the NIR galaxy luminosity function (LF) at z>0.1 should be higher than that measured for z<0.1. Here we present a highly complete (> 90%) spectroscopic sample of 1436 galaxies selected in the H-band to study the normalization of the NIR LF at 0.1<z<0.3 and address the question of whether or not we reside in a large local underdensity. We find that for the combination of our six fields, the product phi* L* at 0.1 < z < 0.3 is ~ 30% higher than that measured at lower redshifts. While our statistical errors in this measurement are on the ~10% level, we find the systematics due to cosmic variance may be larger still. We investigate the effects of cosmic variance on our measurement using the COSMOS cone mock catalogs from the Millennium simulation and recent empirical estimates. We find that our survey is subject to systematic uncertainties due to cosmic variance at the 15% level ($1 sigma), representing an improvement by a factor of ~ 2 over previous studies in this redshift range. We conclude that observations cannot yet rule out the possibility that the local universe is under-dense at z<0.1.
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Whitbourn & Shanks (2014) have reported evidence for a local void underdense by ~15% extending to 150-300h-1Mpc around our position in the Southern Galactic Cap (SGC). Assuming a local luminosity function they modelled K- and r-limited number counts and redshift distributions in the 6dFGS/2MASS and SDSS redshift surveys and derived normalised n(z) ratios relative to the standard homogeneous cosmological model. Here we test further these results using maximum likelihood techniques that solve for the galaxy density distributions and the galaxy luminosity function simultaneously. We confirm the results from the previous analysis in terms of the number density distributions, indicating that our detection of the Local Hole in the SGC is robust to the assumption of either our previous, or newly estimated, luminosity functions. However, there are discrepancies with previously published K and r band luminosity functions. In particular the r-band luminosity function has a steeper faint end slope than the r0.1 results of Blanton et al. (2003) but is consistent with the r0.1 results of Montero-Dorta & Prada (2009); Loveday et al. (2012).
In this work we utilise the most recent publicly available type Ia supernova (SN Ia) compilations and implement a well formulated cosmological model based on Lema^{i}tre-Tolman-Bondi metric in presence of cosmological constant $Lambda$ ($Lambda$LTB) to test for signatures of large local inhomogeneities at $zleq0.15$. Local underdensities in this redshift range have been previously found based on luminosity density (LD) data and galaxy number counts. Our main constraints on the possible local void using the Pantheon SN Ia dataset are: redshift size of $z_{rm size}=0.068^{+0.021}_{-0.030}$; density contrast of $deltaOmega_0/Omega_0=-10.5_{-7.4}^{+9.3}%$ between 16th and 84th percentiles. Investigating the possibility to alleviate the $sim9%$ disagreement between measurements of present expansion rate $H_0$ coming from calibrated local SN Ia and high-$z$ cosmic microwave background data, we find large local void to be a very unlikely explanation alone, consistently with previous studies. However, the level of matter inhomogeneity at a scale of $sim$100Mpc that is allowed by SN Ia data, although not expected from cosmic variance calculations in standard model of cosmology, could be the origin of additonal systematic error in distance ladder measurements based on SN Ia. Fitting low-redshift Pantheon data with a cut $0.023<z<0.15$ to the $Lambda$LTB model and to the Taylor expanded luminosity distance formula we estimate that this systematic error amounts to $1.1%$ towards the lower $H_0$ value. A test for local anisotropy in Pantheon SN Ia data yields null evidence. Analysis of LD data provides a constraint on contrast of large isotropic void $deltaOmega_0/Omega_0=-51.9%pm6.3%$, which is in $sim4sigma$ tension with SN Ia results. More data are necessary to better constrain the local matter density profile and understand the disagreement between SN and LD samples
We describe the construction and the properties of the SWIRE-SDSS database, a preliminary derivation of the Far-Infrared Local Luminosity Functions at 24/70/160 micron based on such a database and ways in which VO tools will allow to refine and extend such work.
Local luminosity functions are fundamental benchmarks for high-redshift galaxy formation and evolution studies as well as for models describing these processes. Determining the local luminosity function in the submillimeter range can help to better constrain in particular the bolometric luminosity density in the local Universe, and Herschel offers the first opportunity to do so in an unbiased way by imaging large sky areas at several submillimeter wavelengths. We present the first Herschel measurement of the submillimeter 0<z<0.2 local luminosity function and infrared bolometric (8-1000 $mu$m) local luminosity density based on SPIRE data from the HerMES Herschel Key Program over 14.7 deg^2. Flux measurements in the three SPIRE channels at 250, 350 and 500 mum are combined with Spitzer photometry and archival data. We fit the observed optical-to-submillimeter spectral energy distribution of SPIRE sources and use the 1/V_{max} estimator to provide the first constraints on the monochromatic 250, 350 and 500 mum as well as on the infrared bolometric (8-1000 mum) local luminosity function based on Herschel data. We compare our results with modeling predictions and find a slightly more abundant local submillimeter population than predicted by a number of models. Our measurement of the infrared bolometric (8-1000 mum) local luminosity function suggests a flat slope at low luminosity, and the inferred local luminosity density, 1.31_-0.21^+0.24 x 10^8 Lsun Mpc^-3, is consistent with the range of values reported in recent literature.
We address the fundamental question of matching the rest-frame K-band luminosity function (LF) of galaxies over the Hubble time using semi-analytic models, after modification of the stellar population modelling. We include the Maraston evolutionary synthesis models, that feature a higher contribution by the Thermally Pulsating - Asymptotic Giant Branch (TP-AGB) stellar phase, into three different semi-analytic models, namely the De Lucia and Blaizot version of the Munich model, MORGANA and the Menci model. We leave all other input physics and parameters unchanged. We find that the modification of the stellar population emission can solve the mismatch between models and the observed rest-frame K-band luminosity from the brightest galaxies derived from UKIDSS data at high redshift. For all explored semi-analytic models this holds at the redshifts - between 2 and 3 - where the discrepancy was recently pointed out. The reason for the success is that at these cosmic epochs the model galaxies have the right age (~1 Gyr) to contain a well-developed TP-AGB phase which makes them redder without the need of changing their mass or age. At the same time, the known overestimation of the faint end is enhanced in the K-band when including the TP-AGB contribution. At lower redshifts (z<2) some of the explored models deviate from the data. This is due to too short merging timescales and inefficient radio-mode AGN feedback. Our results show that a strong evolution in mass predicted by hierarchical models is compatible with no evolution on the bright-end of the K-band LF from z=3 to the local universe. This means that, at high redshifts and contrary to what is commonly accepted, K-band emission is not necessarily a good tracer of galaxy mass.
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