The VIMOS Public Extragalactic Redshift Survey (VIPERS): An unbiased estimate of the growth rate of structure at hzi = 0.85 using the clustering of luminous blue galaxies

Mohammad, F. G.; Granett, B. R.; Guzzo, L.; Bel, J.; Branchini, E.; De La Torre, S.; Moscardini, L.; Peacock, J. A.; Bolzonella, M.; Garilli, B.; Scodeggio, M.; Abbas, U.; Adami, C.; Bottini, D.; Cappi, A.; Cucciati, O.; Davidzon, I.; Franzetti, P.; Fritz, A.; Iovino, A.; Krywult, J.; Le Brun, V.; Le Fèvre, O.; Maccagni, D.; Małek, K.; Marulli, F.; Polletta, M.; Pollo, A.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zanichelli, A.; Arnouts, S.; Coupon, J.; De Lucia, G.; Ilbert, O.; Moutard, T.

doi:10.1051/0004-6361/201731685

We used the VIMOS Public Extragalactic Redshift Survey (VIPERS) final data release (PDR-2) to investigate the performance of colour-selected populations of galaxies as tracers of linear large-scale motions. We empirically selected volume-limited samples of blue and red galaxies as to minimise the systematic error on the estimate of the growth rate of structure fδ 8 from the anisotropy of the two-point correlation function. To this end, rather than rigidly splitting the sample into two colour classes we defined the red or blue fractional contribution of each object through a weight based on the (U-V) colour distribution. Using mock surveys that are designed to reproduce the observed properties of VIPERS galaxies, we find the systematic error in recovering the fiducial value of fδ 8 to be minimised when using a volume-limited sample of luminous blue galaxies. We modelled non-linear corrections via the Scoccimarro extension of the Kaiser model (with updated fitting formulae for the velocity power spectra), finding systematic errors on fδ 8 of below 1-2%, using scales as small as 5 h -1 Mpc.We interpret this result as indicating that selection of luminous blue galaxies maximises the fraction that are central objects in their dark matter haloes; this in turn minimises the contribution to the measured ϵ(rp;π) from the 1-halo term, which is dominated by non-linear motions. The gain is inferior if one uses the full magnitude-limited sample of blue objects, consistent with the presence of a significant fraction of blue, fainter satellites dominated by non-streaming, orbital velocities. We measured a value of fδ 8 = 0.45±0.11 over the single redshift range 0:6≤z≤1:0, corresponding to an effective redshift for the blue galaxies hzi = 0:85. Including in the likelihood the potential extra information contained in the blue-red galaxy cross-correlation function does not lead to an appreciable improvement in the error bars, while it increases the systematic error.

The VIMOS Public Extragalactic Redshift Survey (VIPERS): An unbiased estimate of the growth rate of structure at hzi = 0.85 using the clustering of luminous blue galaxies

Mohammad, F. G.;Granett, B. R.;Guzzo, L.;Bel, J.;Branchini, E.;De La Torre, S.;Moscardini, L.;Peacock, J. A.;Bolzonella, M.;Garilli, B.;Scodeggio, M.;Abbas, U.;Adami, C.;Bottini, D.;Cappi, A.;Cucciati, O.;Davidzon, I.;Franzetti, P.;Fritz, A.;Iovino, A.;Krywult, J.;Le Brun, V.;Le Fèvre, O.;MacCagni, D.;Małek, K.;Marulli, F.;Polletta, M.;Pollo, A.;Tasca, L. A. M.;Tojeiro, R.;Vergani, D.;Zanichelli, A.;Arnouts, S.;Coupon, J.;De Lucia, G.;Ilbert, O.;Moutard, T.

2018-01-01

Abstract

We used the VIMOS Public Extragalactic Redshift Survey (VIPERS) final data release (PDR-2) to investigate the performance of colour-selected populations of galaxies as tracers of linear large-scale motions. We empirically selected volume-limited samples of blue and red galaxies as to minimise the systematic error on the estimate of the growth rate of structure fδ 8 from the anisotropy of the two-point correlation function. To this end, rather than rigidly splitting the sample into two colour classes we defined the red or blue fractional contribution of each object through a weight based on the (U-V) colour distribution. Using mock surveys that are designed to reproduce the observed properties of VIPERS galaxies, we find the systematic error in recovering the fiducial value of fδ 8 to be minimised when using a volume-limited sample of luminous blue galaxies. We modelled non-linear corrections via the Scoccimarro extension of the Kaiser model (with updated fitting formulae for the velocity power spectra), finding systematic errors on fδ 8 of below 1-2%, using scales as small as 5 h -1 Mpc.We interpret this result as indicating that selection of luminous blue galaxies maximises the fraction that are central objects in their dark matter haloes; this in turn minimises the contribution to the measured ϵ(rp;π) from the 1-halo term, which is dominated by non-linear motions. The gain is inferior if one uses the full magnitude-limited sample of blue objects, consistent with the presence of a significant fraction of blue, fainter satellites dominated by non-streaming, orbital velocities. We measured a value of fδ 8 = 0.45±0.11 over the single redshift range 0:6≤z≤1:0, corresponding to an effective redshift for the blue galaxies hzi = 0:85. Including in the likelihood the potential extra information contained in the blue-red galaxy cross-correlation function does not lead to an appreciable improvement in the error bars, while it increases the systematic error.