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Close Major-merger Pairs at z = 0: Star-forming Galaxies with Pseudobulges

Journal Article · · Research in Astronomy and Astrophysics
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Abstract

We present a study of star-forming galaxies (SFGs) with pseudobulges (bulges with Sérsic indexn< 2) in a local close major-merger galaxy pair sample (H-KPAIR). With data from new aperture photometries in the optical and near-infrared bands (aperture size of 7 kpc) and from the literature, we find that the mean Age of central stellar populations in Spirals with pseudobulges is consistent with that of disky galaxies and is nearly constant against the bulge-to-total ratio (B/T). Paired Spirals have a slightly lower fraction of pure disk galaxies (B/T ≤ 0.1) than their counterparts in the control sample. Compared to SFGs with classical bulges, those with pseudobulges have a higher (>2σ) mean of specific star formation rate (sSFR) enhancement (sSFRenh= 0.33 ± 0.07 versus sSFRenh= 0.12 ± 0.06) and broader scatter (by ∼1 dex). The eight SFGs that have the highest sSFRenhin the sample all have pseudobulges. A majority (69%) of paired SFGs with strong enhancement (having sSFR more than 5 times the median of the control galaxies) have pseudobulges. The Spitzer data show that the pseudobulges in these galaxies are tightly linked to nuclear/circum-nuclear starbursts. Pseudobulge SFGs in S+S and in S+E pairs have significantly (>3σ) different sSFR enhancement, with the means of sSFRenh= 0.45 ± 0.08 and −0.04 ± 0.11, respectively. We find a decrease in the sSFR enhancements with the density of the environment for SFGs with pseudobulges. Since a high fraction (5/11) of pseudobulge SFGs in S+E pairs are in rich groups/clusters (local density N1Mpc≥ 7), the dense environment might be the cause for their low sSFRenh.

Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
2582277
Journal Information:
Research in Astronomy and Astrophysics, Journal Name: Research in Astronomy and Astrophysics Journal Issue: 5 Vol. 24; ISSN 1674-4527
Publisher:
IOP ScienceCopyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

Astronomy &amp; Astrophysics