Close Major-merger Pairs at z = 0: Bulge-to-total Ratio and Star Formation Enhancement

Journal Article · 29 July 2022 · The Astrophysical Journal. Supplement Series

DOI: https://doi.org/10.3847/1538-4365/ac73ec · OSTI ID:1983314

He, Chuan  ^[1]; Xu, Cong Kevin  ^[2]; Domingue, Donovan  ^[3]; Cao, Chen ^[4]; Huang, Jia-sheng  ^[2]

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1. Chinese Academy of Sciences (CAS), Beijing (China); University of Chinese Academy of Sciences (CAS), Beijing (China)
2. Chinese Academy of Sciences (CAS), Beijing (China)
3. Georgia College & State University, Milledgeville, GA (United States)
4. Shandong University (China)

We present a study of the bulge-to-total ratio (B/T) of a Ks-band-selected sample of 88 close major-merger pairs of galaxies (H-KPAIR), based on two-dimensional decompositions of SDSS r-band images with galfit. We investigate the dependence of the interaction-induced specific star formation rate enhancement (sSFR_enh) on the B/T ratio, and the effects of this dependence on the differences between star-forming galaxies (SFGs) in spiral+spiral (S+S) and spiral+elliptical (S+E) pairs. Of all the 132 spiral galaxies in H-KPAIR, the 44 in S+E pairs show higher B/T than those in the 44 S+S pairs, with means of B/T = 0.35 ± 0.05 and B/T = 0.26 ± 0.03, respectively. Furthermore, there is a strong negative dependence of sSFR_enh on the B/T ratio, and only paired SFGs with B/T < 0.3 show significant (>5σ) enhancement. Paired SFGs in S+S pairs show a similar trend, and many disky SFGs (B/T < 0.1) in S+S pairs have strong sSFR enhancements (sSFR_enh > 0.7 dex). For SFGs in S+E pairs, the sSFR has no clear B/T dependence, nor any significant enhancement in any B/T bin. Disky SFGs in S+S pairs show significant (>4σ) enhancement in molecular gas content ($${M}_{{{\rm{H}}}_{2}}/{M}_{\mathrm{star}}$$), while SFGs in S+E pairs have no such enhancement in any B/T bin. No significant enhancement of the total gas content (Mgas/Mstar) is found in any B/T bin for paired galaxies. The star formation efficiency of either the total gas (SFE_gas = SFR/M_gas) or molecular gas ($${\mathrm{SFE}}_{{{\rm{H}}}_{2}}=\mathrm{SFR}/{M}_{{{\rm{H}}}_{2}}$$) does not depend on the B/T ratio. The only significant (> 4σ) SFE enhancement found for paired SFGs is the SFE_gas for disky SFGs in S+S pairs.

• Research Organization: US Department of Energy (USDOE), Washington, DC (United States). Office of Science, Sloan Digital Sky Survey (SDSS)
• Sponsoring Organization: USDOE
• OSTI ID: 1983314
• Journal Information: The Astrophysical Journal. Supplement Series, Journal Name: The Astrophysical Journal. Supplement Series Journal Issue: 2 Vol. 261; ISSN 0067-0049
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English