arXiv subjects

Remco F. J. van der Burg

Publications and source records attributed to Remco F. J. van der Burg.

41 records · Page 3Linked to original sources

arXiv2014

Constraints on the Alignment of Galaxies in Galaxy Clusters from $\sim$14,000 Spectroscopic Members

Torques acting on galaxies lead to physical alignments, but the resulting ellipticity correlations are difficult to predict. As they constitute a major contaminant for cosmic shear studies, it is important to constrain the intrinsic alignment signal observationally. We measured the alignments of satellite galaxies within 90 massive galaxy clusters in the redshift range 0.05<z<0.55 and quantified their impact on the cosmic shear signal. We combined a sample of 38,104 galaxies with spectroscopic redshifts with high-quality data from the Canada-France-Hawaii Telescope. We used phase-space information to select 14,576 cluster members, 14,250 of which have shape measurements and measured three different types of alignment: the radial alignment of satellite galaxies toward the brightest cluster galaxies (BCGs), the common orientations of satellite galaxies and BCGs, and the radial alignments of satellites with each other. Residual systematic effects are much smaller than the statistical uncertainties. We detect no galaxy alignment of any kind out to at least 3 r200. The signal is consistent with zero for both blue and red galaxies, bright and faint ones, and also for subsamples of clusters based on redshift, dynamical mass, and dynamical state. These conclusions are unchanged if we expand the sample with bright cluster members from the red sequence. We augment our constraints with those from the literature to estimate the importance of the intrinsic alignments of satellites compared to those of central galaxies, for which the alignments are described by the linear alignment model. Comparison of the alignment signals to the expected uncertainties of current surveys such as the Kilo-Degree Survey suggests that the linear alignment model is an adequate treatment of intrinsic alignments, but it is not clear whether this will be the case for larger surveys.

astro-ph.CO↗

arXiv2013

A Census of Stellar Mass in 10 Massive Haloes at z~1 from the GCLASS Survey

We study the stellar mass content of massive haloes in the redshift range 0.86<z<1.34, by measuring: (1) The stellar mass in the central galaxy versus total dynamical halo mass. (2) The total stellar mass (including satellites) versus total halo mass. (3) The radial stellar mass and number density profiles for the ensemble halo. We use a Ks-band selected catalogue for the 10 clusters in the Gemini Cluster Astrophysics Spectroscopic Survey (GCLASS), with photometric redshifts and stellar masses measured from 11-band SED fitting. Combining the photometric catalogues with the deep spectroscopic component of GCLASS, we correct the cluster galaxy sample for interlopers. We also perform a dynamical analysis of the cluster galaxies to estimate the halo mass M200 for each cluster based on a measurement of its velocity dispersion. (1) We find that the central galaxy stellar mass fraction decreases with total halo mass, and that this is in reasonable quantitative agreement with measurements from abundance matching studies at z~1. (2) The total stellar mass fractions of these systems decrease with halo mass, indicating that lower mass systems are more efficient at transforming baryons into stars. We find the total stellar mass to be a good proxy for total halo mass, with a small intrinsic scatter. When we compare these results with literature measurements, we find that the stellar mass fraction at fixed halo mass shows no significant evolution in the range 0<z<1. (3) We measure a relatively high NFW concentration parameter c ~ 7 for the stellar mass distribution in these clusters. A simple model shows that the stellar mass content of GCLASS can evolve in typical distributions observed at lower redshifts if the clusters primarily accrete stellar mass onto the outskirts. [Abridged]

astro-ph.CO↗

arXiv2013

The environmental dependence of the stellar mass function at z~1: Comparing cluster and field between the GCLASS and UltraVISTA surveys

We present the stellar mass functions (SMFs) of star-forming and quiescent galaxies from observations of 10 rich clusters in the Gemini Cluster Astrophysics Spectroscopic Survey (GCLASS) in the redshift range 0.86<z<1.34. We compare our results with field measurements at similar redshifts using data from a Ks-band selected catalogue of the COSMOS/UltraVISTA field. We construct a Ks-band selected multi-colour catalogue for the clusters in 11 photometric bands covering u-8um, and estimate photometric redshifts and stellar masses using SED fitting techniques. To correct for interlopers in our cluster sample, we use the deep spectroscopic component of GCLASS, which contains spectra for 1282 identified cluster and field galaxies taken with Gemini/GMOS. Both the photometric and spectroscopic samples are sufficiently deep that we can probe the SMF down to masses of 10^10 Msun. We distinguish between star-forming and quiescent galaxies using the rest-frame U-V versus V-J diagram, and find that the best-fitting Schechter parameters alpha and M* are similar within the uncertainties for these galaxy types within the different environments. However, there is a significant difference in the shape and normalisation of the total SMF between the clusters and the field sample. This difference in the total SMF is primarily a reflection of the increased fraction of quiescent galaxies in high-density environments. We apply a simple quenching model that includes components of mass- and environment-driven quenching, and find that in this picture 45% of the star-forming galaxies, which normally would be forming stars in the field, are quenched by the cluster. If galaxies in clusters and the field quench their star formation via different mechanisms, these processes have to conspire in such a way that the shapes of the quiescent and star-forming SMF remain similar in these different environments.

astro-ph.CO↗

arXiv2010

The UV galaxy luminosity function at z=3-5 from the CFHT Legacy Survey Deep fields

We measure and study the evolution of the UV galaxy Luminosity Function (LF) at z=3-5 from the largest high-redshift survey to date, the Deep part of the CFHT Legacy Survey. We also give accurate estimates of the SFR density at these redshifts. We consider ~100,000 Lyman-break galaxies at z~3.1, 3.8 & 4.8 selected from very deep ugriz images of this data set and estimate their rest-frame 1600A luminosity function. Due to the large survey volume, cosmic variance plays a negligible role. Furthermore, we measure the bright end of the LF with unprecedented statistical accuracy. Contamination fractions from stars and low-z galaxy interlopers are estimated from simulations. To correct for incompleteness, we study the detection rate of simulated galaxies injected to the images as a function of magnitude and redshift. We estimate the contribution of several systematic effects in the analysis to test the robustness of our results. We find the bright end of the LF of our u-dropout sample to deviate significantly from a Schechter function. If we modify the function by a recently proposed magnification model, the fit improves. For the first time in an LBG sample, we can measure down to the density regime where magnification affects the shape of the observed LF because of the very bright and rare galaxies we are able to probe with this data set. We find an increase in the normalisation, $ϕ^{*}$, of the LF by a factor of 2.5 between z~5 and z~3. The faint-end slope of the LF does not evolve significantly between z~5 and z~3. We do not find a significant evolution of the characteristic magnitude in the studied redshift interval. The SFR density is found to increase by a factor of ~2 from z~5 to z~4. The evolution from z~4 to z~3 is less eminent.

astro-ph.CO↗

arXiv2010

Grain growth across protoplanetary discs: 10-micron silicate feature versus millimetre slope

Young stars are formed within dusty discs. The grains in the disc are originally of the same size as interstellar dust. Models predict that these grains will grow in size through coagulation. Observations of the silicate features at micron wavelengths are consistent with growth to micron sizes whereas the slope of the SED at longer wavelengths traces growth up to mm sizes. We here look for a correlation between these two grain growth indicators. A large sample of T-Tauri and Herbig-Ae/Be stars was observed with the Spitzer Space Telescope at 5-13 micron; a subsample was observed at mm wavelengths. We complement this subsample with data from the literature to maximise the overlap between micron and mm observations and search for correlations. Synthetic spectra are produced to determine which processes may produce the dust evolution. Dust disc masses in the range <1 to 7 x 10^-4 MSun are obtained. Most sources have a mm spectral slope consistent with grain growth. There is a tentative correlation between the 10-micron silicate feature and the mm slope of the SED. The observed sources seem to be grouped per star-forming region in the micron-vs-mm diagram. The modelling results show that the 10-micron feature becomes flatter and subsequently the mm slope becomes shallower. Grain size distributions shallower than that of the ISM and/or bright central stars are required to explain specific features. Settling of larger grains towards the disc midplane affects the 10-micron feature, but hardly the mm slope. The tentative correlation between the strength of the 10-micron feature and the mm slope suggests that the inner and outer disc evolve simultaneously. Dust with a mass dominated by mm-sized grains is required to explain the shallowest mm slopes. Other processes besides grain growth may also be responsible for the removal of small grains.

astro-ph.SR↗