THE DYNAMICS OFz= 0.8 Hα-SELECTED STAR-FORMING GALAXIES FROM KMOS/CF-HiZELS

Abstract

We present the spatially resolved Hα dynamics of 16 star-forming galaxies at z ∼ 0.81 using the new KMOS multi-object integral field spectrograph on the ESO Very Large Telescope. These galaxies, selected using 1.18 µm narrow-band imaging from the 10 deg 2 CFHT-HiZELS survey of the SA 22 hr field, are found in a ∼ 4 Mpc over-density of Hα emitters and likely reside in a group/intermediate environment, but not a cluster. We confirm and identify a rich group of star-forming galaxies at z = 0.813 ± 0.003, with 13 galaxies within 1000 km s −1 of each other, and seven within a diameter of 3 Mpc. All our galaxies are "typical" star-forming galaxies at their redshift, 0.8 ±0.4 SFR * z=0.8 , spanning a range of specific star formation rates (sSFRs) of 0.2-1.1 Gyr −1 and have a median metallicity very close to solar of 12 + log(O/H) = 8.62 ± 0.06. We measure the spatially resolved Hα dynamics of the galaxies in our sample and show that 13 out of 16 galaxies can be described by rotating disks and use the data to derive inclination corrected rotation speeds of 50-275 km s −1 . The fraction of disks within our sample is 75% ± 8%, consistent with previous results based on HST morphologies of Hα-selected galaxies at z ∼ 1 and confirming that disks dominate the star formation rate density at z ∼ 1. Our Hα galaxies are well fitted by the z ∼ 1 − 2 Tully-Fisher (TF) relation, confirming the evolution seen in the zero-point. Apart from having, on average, higher stellar masses and lower sSFRs, our group galaxies at z = 0.81 present the same mass-metallicity and TF relation as z ∼ 1 field galaxies and are all disk galaxies.

A relationship between specific star formation rate and metallicity gradient within z ∼ 1 galaxies from KMOS-HiZELS

“…Despite the relatively short integration time (1.25 h on source), the data yield clear rotation curves which turn over (or flatten) for at least 10 of these galaxies (see also Sobral et al 2013b). Table 1.…”

“…The survey yields ∼3000 robust Hα emitters at z = 0.81 ± 0.01 (see Sobral et al 2013a and Sobral et al in preparation for details on the spectroscopic and photometric redshifts, and colour-colour selection). We use the wealth of ancillary data, including seven-band photometric coverage [from u to K band, available in this field from the CFHT Legacy Survey (CFHTLS) and the United Kingdom Infrared Telescope Infrared Deep Sky Survey (UKIDSS)] to compute stellar masses for all of the Hα emitters in the parent sample following Sobral et al (2011Sobral et al ( , 2014 Both of these observations were taken as part of the KMOS SV, and so we label the two fields KMOS-HiZELS-SV1 (see also Sobral et al 2013b) and KMOS-HiZELS-SV2 (this paper), respectively.…”

“…These galaxies are drawn from our large (10 square degree) narrow-band (NB) Hα survey in SA22 using WIRcam/Canada-France-Hawaii Telescope (CFHT; CF-HiZELS; Sobral et al in preparation;Sobral et al 2013b;Matthee et al 2014). Due to the depth achieved by our observations (∼0.2 L * z=0.8 ), the majority of our targets are 'typical' galaxies at this epoch which will likely evolve into ∼ L * (or SFR * ) galaxies by z = 0.…”

“…These observations provide spatially resolved Hα and [N II] measurements which allow us to obtain resolved dynamics and metallicities. The dynamical results for the first region are presented in Sobral et al (2013b). In this paper, we use the combined data set from both regions to investigate the chemical abundance gradients and the dynamical properties of the galaxies.…”

Galaxy Growth at Early Times from 3D Studies

“…We can look forward to a great many new findings over the next few years from our KMOS 3D and other surveys undertaken with KMOS (e.g., Sobral et al 2013;Stott et al 2014) in conjunction with high resolution AO-assisted IFU follow-ups and multiwavelength information -a new era in near-IR IFU studies has begun!…”