hCOSMOS: A Dense Spectroscopic Survey of r ≤ 21.3 Galaxies in the COSMOS field

Abstract

We describe the hCOSMOS redshift survey of the COSMOS field conducted with the Hectospec spectrograph on the MMT. In the central 1 deg 2 , the hCOS20.6 subset of the survey is > 90% complete to a limiting r = 20.6. The hCOSMOS survey includes 1701 new redshifts in the COSMOS field. We also use the total of 4362 new and remeasured objects to derive the age sensitive D n 4000 index over the entire redshift interval 0.001 z 0.6. For 85% of the quiescent galaxies in hCOS20.6, we measure the central line-of-sight velocity dispersion. To explore potential uses of this survey, we combine previously measured galaxy sizes, profiles and stellar masses with the spectroscopy. The comparison reveals the known relations among structural, kinematic, and stellar population properties. We also compare redshift and D n 4000 distributions of hCOS20.6 galaxies with SHELS; a complete spectroscopic survey of 4 deg 2 observed to the same depth. The redshift distributions in the two fields are very different but the D n 4000 distribution is remarkably similar. The relation between velocity dispersion and stellar mass for massive hCOS20.6 galaxies is consistent with the local relation from SDSS. Using measured velocity dispersions, we test a photometric proxy calibrated to galaxies in the local universe. The systematic differences between the measured and photometric proxy velocity dispersions are correlated with galaxy dynamical and stellar population properties highlighting the importance of direct spectroscopic measurements.

The OTELO survey

“…From the first photographic atlases (e.g. those of Sandage 1961;Arp 1966) to the most recent and ongoing surveys, such as SDSS (Strauss et al 2002), VVDS-CFDS (Le Fèvre et al 2004), zCOSMOS (Lilly et al 2007), GAMA (Driver et al 2009) DEEP2 (Newman et al 2013), eBOSS (Dawson et al 2016), DES (Dark Energy Survey Collaboration 2016), DEVILS (Davies et al 2018), hCOSMOS (Damjanov et al 2018), VANDELS (McLure et al 2018), and VIPERS (Scodeggio et al 2018), the number and variety of extragalactic explorations have resulted in a growing understanding of the key connections between physical processes and fundamental galaxy observables. In view of this, realistic model-based mock catalogues of galaxies are needed to isolate the net effects and uncertainties of determined physical galaxy properties on observed galaxies, depending on the techniques used to gather real galaxy data.…”

Stacked phase-space density of galaxies around massive clusters: Comparison of dynamical and lensing masses

“…To quantify environmental effects around massive clusters, we use the spectroscopic data sets taken in the hCOSMOS survey (Damjanov et al 2018). The hCOSMOS is the redshift survey of the COSMOS field conducted with the Hectospec spectrograph on the MMT.…”

The HectoMAP Redshift Survey: First Data Release

“…The mean redshift offset between Hectospec and SDSS/BOSS is insensitive to the S/N of the Hectospec spectra; the external error increases with decreasing S/N as expected. Damjanov et al (2018) use 2661 overlapping objects to find that Hectospec redshifts exceed their zCOSMOS counterparts by a small zero-point offset of 17 ± 2 km s −1 .…”

“…Table 3 lists the fraction of galaxies with D n 4000 > 1.5 in each subsample. We use this cut as a proxy for identifying the quiescent population (e.g., Moresco et al (2013), Damjanov et al (2018)). Because of the red selection, quiescent galaxies dominate HectoMAP DR1.…”

“…The SHELS survey (Geller et al 2016), complete to an extinction corrected R = 20.2 over roughly 8 square degrees, also provides a benchmark for more extensive color-selected surveys. An MMT survey of the COS-MOS field, hCOSMOS, provides additional photometric and spectroscopic calibration (Damjanov et al 2018).…”