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Register a new userThe X-ray Luminosity Function of Bright Clusters in the Local Universe
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We present the X-ray luminosity function (XLF) for clusters of galaxies derived from the RASS1 Bright Sample. The sample, selected from the ROSAT All-Sky Survey in a region of 2.5 sr within the southern Galactic cap, contains 130 clusters with flux limits in the range ~ 3-4 x 10^-12 ergs/cm^2/s in the 0.5-2.0 keV band. A maximum-likelihood fit with a Schechter function of the XLF over the entire range of luminosities (0.045 - 28. x 10^44 ergs/s), gives alpha = 1.52 +/- 0.11, L_* = 3.80 +0.70 -0.55 x 10^44 ergs/s, and A = 5.07 +/- 0.45 x 10^-7 Mpc^-3 (10^44 ergs/s)^(alpha-1). We investigate possible evolutionary effects within the sample, out to our redshift limit (z ~ 0.3), finding no evidence for evolution. Our results are in good agreement with other local estimates of the XLF, implying that this statistic for the local universe is now well determined. Comparison with XLFs for distant clusters (0.3 < z < 0.6), shows that no evolution is present for L_X < 10^{44} ergs/s. However, we detect differences at the 3 sigma level, between our local XLF and the distant one estimated by Henry et al. for the EMSS sample. This difference is still present when considering the EMSS sample revised by Nichol et al.
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The measurement of the Star Formation Rate density of the Universe is of prime importance in understanding the formation and evolution of galaxies. The [OII]3727 emission line flux, easy to measure up to z~1.4 within deep redshift surveys in the optical and up to z~5.4 in the near infrared, offers a reliable means of characterizing the star formation properties of high-z objects. In order to provide the high-z studies with a local reference, we have measured total [OII]3727 fluxes for the well analyzed local sample of star-forming galaxies from the Universidad Complutense de Madrid Survey. This data is used to derive the [OII]3727 luminosity function for local star-forming galaxies. When compared with similar luminosity densities published for redshift up to z~1, the overall evolution already observed in the star formation activity of the Universe is confirmed.
We investigate the relationship between soft xray luminosity and mass for low redshift clusters of galaxies by comparing observed number counts to expectations of $Lambda$CDM cosmologies. We use a three-parameter model for the conditional probability of luminosity given mass and epoch, described as a log-normal distribution of fixed width centered on a power-law scaling relation, $L spropto M^prhoc^s(z)$. We use an ensemble of simulated clusters to argue that the observed, intrinsic variance in the temperature--luminosity relation is directly indicative of mass--luminosity variance, and derive $sigm se 0.43 pm 0.06$ from HIFLUGCS data. Adding this to the likelihood analysis results in best-fit estimates $p se 1.59 pm 0.05$, $lnlf se 1.34 pm 0.09$, and $sigm se 0.37 pm 0.05$ for self-similar redshift evolution in a concordance ($Omega_m se 0.3$, $Omega_Lambda se 0.7$, $sigma_8 se0.9$) universe. We show that the present-epoch intercept is very sensitive to power spectrum normalization, $lnlf spropto sigate^{-4}$, and the slope is weakly sensitive to the matter density, $p spropto Omega_m^{1/2}$. The intercept derived here is dimmer by a factor 2, and slope slightly steeper, than the L-M relation published using hydrostatic mass estimates of the HIFLUGCS sample. We show that this discrepancy is largely due to Malmquist bias of the xray flux-limited sample. In light of new WMAP constraints, we discuss the interplay between parameters and sources of systematic error, and offer a compromise model with $Omega_m se 0.24$, $sigma_8 se 0.85$, and somewhat lower scatter $sigm se 0.25$, in which hydrostatic mass estimates remain accurate to $ssim 15%$. We stress the need for independent calibration of the L-M relation via weak gravitational lensing.
Large area catalogs of galaxy clusters constructed from ROSAT All Sky Survey provide the base for our knowledge on the population of clusters thanks to the long-term multiwavelength efforts on their follow-up. Advent of large area photometric surveys superseding in depth previous all-sky data allows us to revisit the construction of X-ray cluster catalogs, extending the study to lower cluster masses and to higher redshifts and to provide the modelling of the selection function. We perform a wavelet detection of X-ray sources and make extensive simulations of the detection of clusters in the RASS data. We assign an optical richness to each of the 24,788 detected X-ray sources in the 10,382 square degrees of SDSS BOSS area, using redMaPPer version 5.2. We name this survey COnstrain Dark Energy with X-ray (CODEX) clusters. We show that there is no obvious separation of sources on galaxy clusters and AGN, based on distribution of systems on their richness. This is a combination of increasing number of galaxy groups and their selection as identification of an X-ray sources either by chance or due to groups hosting an AGN. To clean the sample, we use a cut on the optical richness at the level corresponding to the 10% completeness of the survey and include it into the modelling of cluster selection function. We present the X-ray catalog extending to a redshift of 0.6 down to X-ray fluxes of $10^{-13}$ ergs s$^{-1}$ cm$^{-2}$. We provide the modelling of the sample selection and discuss the redshift evolution of the high end of the X-ray luminosity function (XLF). Our results on $z<0.3$ XLF are in agreement with previous studies, while we provide new constraints on the $0.3<z<0.6$ XLF. We find a lack of strong redshift evolution of the XLF, provide exact modeling of the effect of low number statistics and AGN contamination and present the resulting constraints on the flat $Lambda$CDM.
We present the results of a determination of the galaxy luminosity function at ultraviolet wavelengths at redshifts of $z=0.0-0.1$ from GALEX data. We determined the luminosity function in the GALEX FUV and NUV bands from a sample of galaxies with UV magnitudes between 17 and 20 that are drawn from a total of 56.73 deg^2 of GALEX fields overlapping the b_j-selected 2dF Galaxy Redshift Survey. The resulting luminosity functions are fainter than previous UV estimates and result in total UV luminosity densities of 10^(25.55+/-0.12) ergs s^-1 Hz^-1 Mpc^-3 and 10^(25.72+/-0.12) ergs s^-1 Hz^-1 Mpc^-3 at 1530 Ang. and 2310 Ang., respectively. This corresponds to a local star formation rate density in agreement with previous estimates made with H-alpha-selected data for reasonable assumptions about the UV extinction.
We show how to improve constraints on Omega_m, sigma_8, and the dark-energy equation-of-state parameter, w, obtained by Mantz et al. (2008) from measurements of the X-ray luminosity function of galaxy clusters, namely MACS, the local BCS and the REFLEX galaxy cluster samples with luminosities L> 3 times 10^{44} erg/s in the 0.1--2.4 keV band. To this aim, we use Tinker et al. (2008) mass function instead of Jenkins et al. (2001) and the M-L relationship obtained from Del Popolo (2002) and Del Popolo et al. (2005). Using the same methods and priors of Mantz et al. (2008), we find, for a Lambda$CDM universe, Omega_m=0.28^{+0.05}_{-0.04} and sigma_8=0.78^{+0.04}_{-0.05}$ while the result of Mantz et al. (2008) gives less tight constraints $Omega_m=0.28^{+0.11}_{-0.07}$ and sigma_8=0.78^{+0.11}_{-0.13}. In the case of a wCDM model, we find Omega_m=0.27^{+0.07}_{-0.06}, $sigma_8=0.81^{+0.05}_{-0.06}$ and $w=-1.3^{+0.3}_{-0.4}$, while in Mantz et al. (2008) they are again less tight Omega_m=0.24^{+0.15}_{-0.07}, sigma_8=0.85^{+0.13}_{-0.20} and w=-1.4^{+0.4}_{-0.7}. Combining the XLF analysis with the f_{gas}+CMB+SNIa data set results in the constraint Omega_m=0.269 pm 0.012, sigma_8=0.81 pm 0.021 and w=-1.02 pm 0.04, to be compared with Mantz et al. (2008), Omega_m=0.269 pm 0.016, sigma_8=0.82 pm 0.03 and w=-1.02 pm 0.06. The tightness of the last constraints obtained by Mantz et al. (2008), are fundamentally due to the tightness of the $f_{gas}$+CMB+SNIa constraints and not to their XLF analysis. Our findings, consistent with w=-1, lend additional support to the cosmological-constant model.
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