arXiv subjects

L. Denneau

Publications and source records attributed to L. Denneau.

39 records · Page 3Linked to original sources

arXiv2013

The Pan-STARRS1 Medium-Deep Survey: The role of galaxy group environment in the star formation rate versus stellar mass relation and quiescent fraction out to $z \sim 0.8$

Using a large sample of field and group galaxies drawn from the Pan-STARRS1 Medium-Deep Survey, we present the specific star formation rate (SSFR) - stellar mass (M*) relation, as well as the quiescent fraction versus M* relation in different environments. We confirm that the fraction of quiescent galaxies is strongly dependent on environment at a fixed stellar mass, but that the amplitude and the slope of the star-forming sequence is similar between the field and groups: in other words, the SSFR-density relation at a fixed stellar mass is primarily driven by the change in the star-forming and quiescent fractions between different environments rather than a global suppression in the star formation rate for the star-forming population. However, when we restrict our sample to the cluster-scale environments ($M>10^{14}M_{solar}$), we find a global reduction in the SSFR of the star forming sequence of $17\%$ at 4$σ$ confidence as opposed to its field counterpart. After removing the stellar mass dependence of the quiescent fraction seen in field galaxies, the excess in the quiescent fraction due to the environment quenching in groups and clusters is found to increase with stellar mass. We argue that these results are in favor of galaxy mergers to be the primary environment quenching mechanism operating in galaxy groups whereas strangulation is able to reproduce the observed trend in the environment quenching efficiency and stellar mass relation seen in clusters. Our results also suggest that the relative importance between mass quenching and environment quenching depends on stellar mass -- the mass quenching plays a dominant role in producing quiescent galaxies for more massive galaxies, while less massive galaxies are quenched mostly through the environmental effect, with the transition mass around $1-2\times10^{10}M_{solar}$ in the group/cluster environment. (abridged)

astro-ph.CO↗

arXiv2013

The Pan-STARRS1 Small Area Survey 2

The Pan-STARRS1 survey is acquiring multi-epoch imaging in 5 bands (grizy) over the entire sky north of declination -30deg (the $3π$ survey). In July 2011 a test area of about 70 sq.deg. was observed to the expected final depth of the main survey. In this, the first of a series of papers targetting the galaxy count and clustering properties of the combined multi-epoch test area data, we present a detailed investigation into the depth of the survey and the reliability of the Pan-STARRS1 analysis software. We show that the Pan-STARRS1 reduction software can recover the properties of fake sources, and show good agreement between the magnitudes measured by Pan-STARRS1 and those from Sloan Digital Sky Survey. We also examine the number of false detections apparent in the Pan-STARRS1 data. Our comparisons show that the test area survey is somewhat deeper than the Sloan Digital Sky Survey in all bands, and, in particular, the z band approaches the depth of the stacked Sloan Stripe 82 data.

astro-ph.CO↗

arXiv2011

NEOWISE Observations of Near-Earth Objects: Preliminary Results

With the NEOWISE portion of the \emph{Wide-field Infrared Survey Explorer} (WISE) project, we have carried out a highly uniform survey of the near-Earth object (NEO) population at thermal infrared wavelengths ranging from 3 to 22 $μ$m, allowing us to refine estimates of their numbers, sizes, and albedos. The NEOWISE survey detected NEOs the same way whether they were previously known or not, subject to the availability of ground-based follow-up observations, resulting in the discovery of more than 130 new NEOs. The survey's uniformity in sensitivity, observing cadence, and image quality have permitted extrapolation of the 428 near-Earth asteroids (NEAs) detected by NEOWISE during the fully cryogenic portion of the WISE mission to the larger population. We find that there are 981$\pm$19 NEAs larger than 1 km and 20,500$\pm$3000 NEAs larger than 100 m. We show that the Spaceguard goal of detecting 90% of all 1 km NEAs has been met, and that the cumulative size distribution is best represented by a broken power law with a slope of 1.32$\pm$0.14 below 1.5 km. This power law slope produces $\sim13,200\pm$1,900 NEAs with $D>$140 m. Although previous studies predict another break in the cumulative size distribution below $D\sim$50-100 m, resulting in an increase in the number of NEOs in this size range and smaller, we did not detect enough objects to comment on this increase. The overall number for the NEA population between 100-1000 m are lower than previous estimates. The numbers of near-Earth comets will be the subject of future work.

astro-ph.EP↗