A MAGNIFIED VIEW OF THE KINEMATICS AND MORPHOLOGY OF RCSGA 032727-132609: ZOOMING IN ON A MERGER ATz= 1.7

Abstract

We present a detailed analysis of multi-wavelength HST/WFC3 imaging and Keck/OSIRIS near-IR AO-assisted integral field spectroscopy for a highly magnified lensed galaxy at z = 1.70. This young starburst is representative of UV-selected star-forming galaxies (SFG) at z ∼ 2 and contains multiple individual star-forming regions. Due to the lensing magnification, we can resolve spatial scales down to 100 pc in the source plane of the galaxy. The velocity field shows disturbed kinematics suggestive of an ongoing interaction, and there is a clear signature of a tidal tail. We constrain the age, reddening, SFR and stellar mass of the star-forming clumps from SED modelling of the WFC3 photometry and measure their Hα luminosity, metallicity and outflow properties from the OSIRIS data. With strong star formation driven outflows in four clumps, RCSGA0327 is the first high redshift SFG at stellar mass < 10 10 M ⊙ with spatially resolved stellar winds. We compare the Hα luminosities, sizes and dispersions of the star-forming regions to other high-z clumps as well as local giant H II regions and find no evidence for increased clump star formation surface densities in interacting systems, unlike in the local Universe. Spatially resolved SED modelling unveils an established stellar population at the location of the largest clump and a second mass concentration near the edge of the system which is not detected in Hα emission. This suggests a picture of an equal-mass mixed major merger, which has not triggered a new burst of star formation or caused a tidal tail in the gas-poor component.

On the Stellar Masses of Giant Clumps in Distant Star-forming Galaxies

“…Our sample comprises a total of 241 stellar clumps hosted in 40 galaxies from Förster Schreiber et al (2011), Guo et al (2012), Adamo et al (2013), Elmegreen et al (2013), and Wuyts et al (2014). These five clump datasets are described in Table 1.…”

“…Adamo et al (2013) have used the Cluster Lensing And Supernova survey with Hubble (CLASH, Postman et al 2012) to analyse clumps in the filters F390W, F475W, F555W, F606W, F775W, F814W, and F850LP from HST/ACS, and the filters F105W, F110W, F125W, and F160W from HST/WFC3. And, Wuyts et al (2014) had at disposal observations in the HST/WFC3 filters F390W, F606W, F814W, F098M, F125W, and F160W. For the typical redshift z ∼ 2 of the studied clumpy host galaxies, the longest wavelength observations available at 1.6 µm for all cover the rest-frame optical emission of the stellar clumps.…”

RESOLVED STAR FORMATION ON SUB-GALACTIC SCALES IN A MERGER ATz= 1.7

“…The inset panel is the reconstruction of the source from the lens model described in Sharon et al (2012). Stellar mass surface density maps suggest that the stellar populations in clump g were established earlier than the other starforming clumps, and clump g is merging with an old, red (faint) stellar population at the right side of the reconstructed image (Wuyts et al 2014). The bright starforming knots in between are likely a result of the interaction, as demonstrated herein.…”

Galaxy Growth at Early Times from 3D Studies

“…Other near-IR IFU surveys in the range 1 < z < 3.5 have targeted galaxies with various selection criteria, probing somewhat different mass/luminosity ranges and/or focussing on different redshift intervals, and include among others "MAS-SIV" (e.g., Épinat et al 2009Contini et al 2012), "AMAZE" and "LSD" (e.g., Gnerucci et al 2011a,b), "WiggleZ" (Wisnioski et al 2011(Wisnioski et al , 2012, "sHiZELs" (Swinbank et al 2012a,b), the "BX/BM" OSIRIS samples (Law et al , 2012Wright et al 2009). A small but important set of strongly lensed z > 1 galaxies was also observed with near-IR IFUs, reaching an effective resolution on sub-kpc scales in the source plane and even as small as 100 − 200 pc in a few cases (Stark et al 2008;Jones et al 2010aJones et al ,b, 2013Yuan et al 2011Yuan et al , 2012Wuyts et al 2014a).…”