IROCKS: SPATIALLY RESOLVED KINEMATICS OF z ∼ 1 STAR-FORMING GALAXIES

Abstract

We present results from IROCKS (Intermediate Redshift OSIRIS Chemo-Kinematic Survey) for sixteen z ∼ 1 and one z ∼ 1.4 star-forming galaxies. All galaxies were observed with OSIRIS with the laser guide star adaptive optics system at Keck Observatory. We use rest-frame nebular Hα emission lines to trace morphologies and kinematics of ionized gas in star-forming galaxies on sub-kiloparsec physical scales. We observe elevated velocity dispersions (σ 50 km s −1 ) seen in z > 1.5 galaxies persist at z ∼ 1 in the integrated galaxies. Using an inclined disk model and the ratio of v/σ, we find that 1/3 of the z ∼ 1 sample are disk candidates while the other 2/3 of the sample are dominated by merger-like and irregular sources. We find that including extra attenuation towards HII regions derived from stellar population synthesis modeling brings star formation rates (SFR) using Hα and stellar population fit into a better agreement. We explore properties of compact Hα sub-component, or "clump," at z ∼ 1 and find that they follow a similar size-luminosity relation as local HII regions but are scaled-up by an order of magnitude with higher luminosities and sizes. Comparing the z ∼ 1 clumps to other high-redshift clump studies, we determine that the clump SFR surface density evolves as a function of redshift. This may imply clump formation is directly related to the gas fraction in these systems and support disk fragmentation as their formation mechanism since gas fraction scales with redshift.

z ∼ 2: An Epoch of Disk Assembly

“…As first shown in K12, s g roughly doubles over < < z 0.1 1.2, which spans approximately 8 Gyr. Although the time from = z 1 to = z 2 is much shorter, only 3 Gyr, we find a significant evolution in s g during this period (see also e.g., Mieda et al 2016). The median value of σ g increases from 40 to 70 km s −1 .…”

Clumpy Galaxies in CANDELS. II. Physical Properties of UV-bright Clumps at 0.5 ≤ z < 3

“…These clumps are seen in deep and high-resolution rest-frame UV and optical images (e.g., Conselice et al 2004;Elmegreen & Elmegreen 2005;Elmegreen et al 2007Elmegreen et al , 2009aFörster Schreiber et al 2011;Guo et al 2012bGuo et al , 2015Wuyts et al 2012;Murata et al 2014;Tadaki et al 2014;Shibuya et al 2016;Soto et al 2017). They are also detected in highresolution emission-line maps of Hα (e.g., Genzel et al 2008Genzel et al , 2011Wisnioski et al 2011;Livermore et al 2012Livermore et al , 2015Mieda et al 2016;Fisher et al 2017a) and CO (e.g., Jones et al 2010;Swinbank et al 2010;Dessauges-Zavadsky et al 2017b). The clumps appear to be much larger, brighter, and more massive than local star-forming regions.…”

“…Their actual sizes are uncertain due to the resolution limit of current observations, ranging from ∼1 kpc (e.g., Elmegreen et al 2007;Förster Schreiber et al 2011) to a few hundred pc (e.g., Livermore et al 2012). The clumps resemble mini-starbursts in their galaxies (e.g., Bournaud et al 2015;Zanella et al 2015) and have specific star formation rates (sSFRs) that are higher than those of their surrounding areas by a factor of several, evident by their blue UV-optical colors or enhanced Hα surface brightness (e.g., Guo et al 2012b;Wuyts et al 2012Wuyts et al , 2013Hemmati et al 2014;Mieda et al 2016).…”

“…Current facilities enable us to resolve distant galaxies and study their spatially resolved physical properties, including (I) substructures (e.g., Elmegreen & Elmegreen 2005;Elmegreen et al 2007Elmegreen et al , 2009aElmegreen et al , 2009bGenzel et al 2008Genzel et al , 2011Förster Schreiber et al 2011;Guo et al 2012bGuo et al , 2015Wuyts et al 2012;Tadaki et al 2014;Shibuya et al 2016;Soto et al 2017), (II) color variation (e.g., Menanteau et al 2004;McGrath et al 2008;Tortora et al 2010;Gargiulo et al 2011Gargiulo et al , 2012Guo et al 2011;Szomoru et al 2011;Boada et al 2015;Tacchella et al 2015b;Chan et al 2016;Liu et al 2016), (III) star formation variation (e.g., Wuyts et al 2013;Hemmati et al 2014Hemmati et al , 2015Tacchella et al 2015a;Barro et al 2016;Mieda et al 2016;Nelson et al 2016aNelson et al , 2016b, and (IV) mass distribution and central concentration (e.g., Saracco et al 2012;Szomoru et al 2013;Lang et al 2014;van Dokkum et al 2014;Barro et al 2017;Mosleh et al 2017).…”

Feedback and Feeding in the Context of Galaxy Evolution withSPICA: Direct Characterisation of Molecular Outflows and Inflows

“…Specifically, the Near Infrared Spectrograph (NIRSpec), which will cover 0.6 − 5.3 µm at R ∼ 2700, and the Mid Infrared Instrument (MIRI), which will cover 4.9 − 28.8 µm at R ∼ 1500 − 3500, will both have Integral Field Unit (IFU) modes, enabling high sensitivity, spatially-resolved spectra of star-forming galaxies and AGN. As has been shown in studies of nearby AGN (e.g., Müller-Sánchez et al 2016;Riffel et al 2016) and z ∼ 1 − 2 starbursts (e.g., Genzel et al 2014;Livermore et al 2015;Mieda et al 2016), IFUs are powerful tools to disentangle the excitation and kinematics of the atomic and molecular gas in the nuclei of galaxies. At low redshifts, MIRI and NIRSpec will provide access to rest-frame near-IR and mid-IR diagnostic features that can be used to separate out photoionization and heating from shock excitation, on spatial scales that range from tens to hundreds of parsecs.…”