ترغب بنشر مسار تعليمي؟ اضغط هنا

Measurement of BAO correlations at $z=2.3$ with SDSS DR12 lya-Forests

90   0   0.0 ( 0 )
 نشر من قبل James Rich
 تاريخ النشر 2017
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We use flux-transmission correlations in Lya forests to measure the imprint of baryon acoustic oscillations (BAO). The study uses spectra of 157,783 quasars in the redshift range $2.1le z le 3.5$ from the Sloan Digital Sky Survey (SDSS) Data Release 12 (DR12). Besides the statistical improvements on our previous studies using SDSS DR9 and DR11, we have implemented numerous improvements in the analysis procedure, allowing us to construct a physical model of the correlation function and to investigate potential systematic errors in the determination of the BAO peak position. The Hubble distance, $DHub=c/H(z)$, relative to the sound horizon is $DHub(z=2.33)/r_d=9.07 pm 0.31$. The best-determined combination of comoving angular-diameter distance, $DM$, and the Hubble distance is found to be $DHub^{0.7}DM^{0.3}/r_d=13.94pm0.35$. This value is $1.028pm0.026$ times the prediction of the flat-lcdm model consistent with the cosmic microwave background (CMB) anisotropy spectrum. The errors include marginalization over the effects of unidentified high-density absorption systems and fluctuations in ultraviolet ionizing radiation. Independently of the CMB measurements, the combination of our results and other BAO observations determine the open-lcdm density parameters to be $om=0.296 pm 0.029$, $ol=0.699 pm 0.100$ and $Omega_k = -0.002 pm 0.119$.



قيم البحث

اقرأ أيضاً

[abridged] We present an anisotropic analysis of the baryonic acoustic oscillation (BAO) scale in the twelfth and final data release of the Baryonic Oscillation Spectroscopic Survey (BOSS). We independently analyse the LOWZ and CMASS galaxy samples: the LOWZ sample contains contains 361 762 galaxies with an effective redshift of $z_{rm LOWZ}=0.32$; the CMASS sample consists of 777 202 galaxies with an effective redshift of $z_{rm CMASS}=0.57$. We extract the BAO peak position from the monopole power spectrum moment, $alpha_0$, and from the $mu^2$ moment, $alpha_2$, where $mu$ is the cosine of the angle to the line-of-sight. The $mu^2$-moment provides equivalent information to that available in the quadrupole but is simpler to analyse. After applying a reconstruction algorithm to reduce the BAO suppression by bulk motions, we measure the BAO peak position in the monopole and $mu^2$-moment, which are related to radial and angular shifts in scale. We report $H(z_{rm LOWZ})r_s(z_d)=(11.60pm0.60)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm LOWZ})/r_s(z_d)=6.66pm0.16$ with a cross-correlation coefficient of $r_{HD_A}=0.41$, for the LOWZ sample; and $H(z_{rm CMASS})r_s(z_d)=(14.56pm0.37)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm CMASS})/r_s(z_d)=9.42pm0.13$ with a cross-correlation coefficient of $r_{HD_A}=0.47$, for the CMASS sample. We combine these results with the measurements of the BAO peak position in the monopole and quadrupole correlation function of the same dataset citep[][companion paper]{Cuestaetal2015} and report the consensus values: $H(z_{rm LOWZ})r_s(z_d)=(11.63pm0.69)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm LOWZ})/r_s(z_d)=6.67pm0.15$ with $r_{HD_A}=0.35$ for the LOWZ sample; $H(z_{rm CMASS})r_s(z_d)=(14.67pm0.42)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm CMASS})/r_s(z_d)=9.47pm0.12$ with $r_{HD_A}=0.52$ for the CMASS sample.
62 - B. Hoeneisen 2016
We define Baryon Acoustic Oscillation (BAO) distances $hat{d}_alpha(z, z_c)$, $hat{d}_z(z, z_c)$, and $hat{d}_/(z, z_c)$ that do not depend on cosmological parameters. These BAO distances are measured as a function of redshift $z$ with the Sloan Digi tal Sky Survey (SDSS) data release DR12. From these BAO distances alone, or together with the correlation angle $theta_textrm{MC}$ of the Cosmic Microwave Background (CMB), we constrain the cosmological parameters in several scenarios. We find $4.3 sigma$ tension between the BAO plus $theta_textrm{MC}$ data and a cosmology with flat space and constant dark energy density $Omega_textrm{DE}(a)$. Releasing one and/or the other of these constraints obtains agreement with the data. We measure $Omega_textrm{DE}(a)$ as a function of $a$.
We measure the transverse baryon acoustic oscillations (BAO) signal in the local Universe using a sample of blue galaxies from the Sloan Digital Sky Survey (SDSS) survey as a cosmological tracer. The method is weakly dependent on a cosmological model and is suitable for 2D analyses in thin redshift bins to investigate the SDSS data in the interval $z {in} [0.105, 0.115]$. We detect the transverse BAO signal ${theta}_{BAO} = 19.8^{deg} {pm} 1.05^{deg}$ at $z_{eff} = 0.11$, with a statistical significance of $2.2 {sigma}$. Additionally, we perform tests that confirm the robustness of this angular BAO signature. Supported by a large set of log-normal simulations, our error analyses include statistical and systematic contributions. In addition, considering the sound horizon scale calculated by the Planck Collaboration, $r_{s}^{Planck}$, and the ${theta}_{BAO}$ value obtained here, we obtain a measurement of the angular diameter distance $D_{A}(0.11) = 258.31 {pm} 13.71 ,Mpc/h$. Moreover, combining this ${theta}_{BAO}$ measurement at low redshift with other BAO angular scale data reported in the literature, we perform statistical analyses for the cosmological parameters of some Lambda cold dark matter (${Lambda}$CDM) type models.
We present a new determination of the large-scale clustering of the CIV forest (i.e., the absorption due to all CIV absorbers) using its cross-correlation with quasars in the Sloan Digital Sky Survey (SDSS) Data Release 12 (DR12). We fit a linear bia s model to the measured cross-correlation. We find that the transmission bias of the CIV forest, $b_{Fc}$, at a mean redshift of $z=2.3$, obeys the relation $(1+beta_c)b_{F c} = -0.024 pm 0.003$. Here, $beta_{c}$ is the linear redshift space distortion parameter of the CIV absorption, which can only be poorly determined at $beta_c=1.1pm 0.6$ from our data. This transmission bias is related to the bias of CIV absorbers and their host halos through the effective mean optical depth of the CIV forest, $bartau_c$. Estimating a value $bar tau_c(z) simeq 0.01$ from previous studies of the CIV equivalent width distribution, our measurement implies a CIV absorber bias near unity, with a large error due to uncertainties in both $beta_c$ and $bartau_c$. This makes it compatible with the higher DLA bias $b_{rm DLA}simeq 2$ measured previously from the cross-correlation of DLAs and the Lyman-$alpha$ forest. We discuss the implications of the CIV absorber bias for the mass distribution of their host halos. More accurate determinations of $bar tau_c(z)$ and $beta_c$ are necessary to obtain a more robust measurement of this CIV absorber bias.
We perform a tomographic baryon acoustic oscillations (BAO) analysis using the monopole, quadrupole and hexadecapole of the redshift-space galaxy power spectrum measured from the pre-reconstructed combined galaxy sample of the completed Sloan Digital Sky Survey (SDSS-III) Baryon Oscillation Spectroscopic Survey (BOSS) Data Release (DR)12 covering the redshift range of $0.20<z<0.75$. By allowing for overlap between neighbouring redshift slices, we successfully obtained the isotropic and anisotropic BAO distance measurements within nine redshift slices to a precision of $1.5%-3.4%$ for $D_V/r_d$, $1.8% -4.2%$ for $D_A/r_d$ and $3.7% - 7.5%$ for $H r_d$, depending on effective redshifts. We provide our BAO measurement of $D_A/r_d$ and $H r_d$ with the full covariance matrix, which can be used for cosmological implications. Our measurements are consistent with those presented in citet{Acacia}, in which the BAO distances are measured at three effective redshifts. We constrain dark energy parameters using our measurements, and find an improvement of the Figure-of-Merit of dark energy in general due to the temporal BAO information resolved. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا