Rest-frame UV versus optical morphologies of galaxies using Sersic profile fitting: the importance of morphological K-correction

Abstract

We show a comparison of the rest-frame UV morphologies of a sample of 162 intermediate redshift (median redshift 1.02) galaxies with their rest-frame optical morphologies. We select our sample from the deepest near-UV image obtained with the Hubble Space Telescope (HST) using the WFPC2 (F300W) as part of the parallel observations of the Hubble Ultra Deep Field campaign overlapping with the HST/ACS GOODS dataset. We perform single component Sersic fits in both WFPC2/F300W (rest-frame UV) and ACS/F850LP (rest-frame optical) bands and deduce that the Sersic index $n$ is estimated to be smaller in the rest-frame UV compared to the rest-frame optical, leading to an overestimation of the number of merger candidates by ~40-100% compared to the rest-frame optical depending upon the cutoff in $n$ employed for identifying merger candidates. This effect seems to be dominated by galaxies with low values of n(F300W) <= 0.5 that have a value of n(F850LP) ~ 1.0. We argue that these objects are probably clumpy starforming galaxies or minor mergers, both of which are essentially contaminants, if one is interested in identifying major mergers. In addition we also find evidence that the axis ratio b/a is lower, i.e. ellipticity (1-b/a) is higher in rest-frame UV compared to the rest-frame optical. Moreover, we find that in the rest-frame UV, the number of high ellipticity (e >= 0.8) objects are higher by a factor of ~2.8 compared to the rest-frame optical. This indicates that the reported dominance of elongated morphologies among high-z LBGs might just be a bias related to the use of rest-frame UV datasets in high-z studies.

14 pages, 9 figures, to appear in the Astrophysical Journal

References in corpus (6)

• The Structures of Distant Galaxies I: Galaxy Structures and the Merger Rate to z~3 in the Hubble Ultra-Deep Field
• The Morphological Diversities Among Star-forming Galaxies at High Redshifts in the Great Observatories Origins Deep Survey (GOODS)
• Towards a robust estimate of the merger rate evolution using near-IR photometry
• Far-Ultraviolet Imaging of the Hubble Deep Field North: Star Formation in Normal Galaxies at z<1
• Unravelling the morphologies of Luminous Compact Galaxies using the HST/ACS GOODS survey
• Faint U-Band Dropouts in the WFPC2 Parallels of the Hubble Ultra Deep Field

Cited by in corpus (11)

• MOIRCS Deep Survey IV: Evolution of Galaxy Stellar Mass Function Back to z ~ 3
• Morphologies of local Lyman break galaxy analogs II: A Comparison with galaxies at z=2-4 in ACS and WFC3 images of the Hubble Ultra Deep Field
• Early Results From GLASS-JWST. XII: The Morphology of Galaxies at the Epoch of Reionization
• The evolutionary sequence of sub-mm galaxies: from diffuse discs to massive compact ellipticals?
• The Rest-frame Ultraviolet Light Profile Shapes of Ly-alpha-Emitting Galaxies at z=3.1
• Structures of Local Galaxies Compared to High Redshift Star-forming Galaxies
• On the buildup of massive early-type galaxies at z<~1. I- Reconciling their hierarchical assembly with mass-downsizing
• Deep Extragalactic VIsible Legacy Survey (DEVILS): Stellar Mass Growth by Morphological Type since $z=1$
• SED-inferred properties and morphology of Lyman-break galaxies at $z\sim 1$ in the CDF-S
• JWST Reveals Bulge-dominated Star-forming Galaxies at Cosmic Noon
• A grand-design spiral galaxy 1.5 billion years after the Big Bang with JWST