Close Major-merger Pairs at z=0: Star-forming Galaxies with Pseudobulges
Research in Astronomy and Astrophysics(2024)
摘要
We present a study of star-forming galaxies (SFGs) with pseudobulges (bulges
with Sérsic index n < 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 (>2 σ) mean of specific star formation rate (sSFR) enhancement
(sSFR_enh = 0.33±0.07 vs sSFR_enh = 0.12±0.06) and broader
scatter (by ∼ 1 dex). The eight SFGs that have the highest sSFR_enh in 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
(>3 σ) different sSFR enhancement, with the means of sSFR_enh =
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 N_1Mpc≥ 7), the dense environment
might be the cause for their low sSFR_enh.
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