The role of minor mergers in the recent star formation history of early-type galaxies

By S. Kaviraj, Sébastien Peirani, S. Khochfar, J. Silk, S. Kay. 2007

134 citations recorded by the source corpus.

We demonstrate that the large scatter in the ultra-violet (UV) colours of intermediate- mass early-type galaxies in the local Universe and the inferred low-level recent star formation in these objects can be reproduced by minor mergers in the standardCDM cosmology. Numerical simulations of mergers with mass ratios � 1:4, with reasonable assumptions for the ages, metallicities and dust properties of the merger progenitors, produce good agreement to the observed UV colours of the early-type population, if the infalling satellites are assumed to have (cold) gas fractions � 20%. Early-types that sat- isfy (NUV r) . 3.8 are likely to have experienced mergers with mass ratios between 1:4 and 1:6 within the last � 1.5 Gyrs, while those that satisfy 3.8 < (NUV r) < 5.5 are consistent with either recent mergers with mass ratios � 1:6 or mergers with higher mass ratios that occurred more than � 1.5 Gyrs in the past. We demonstrate that the early-type colour-magnitude relations and colour distributions in both the UV and optical spectral ranges are consistent with the expected frequency of minor merging activity in the standardCDM cosmology at low redshift. We present a strong plausi- bility argument for minor mergers to be the principal mechanism behind the large UV scatter and associated low-level recent star formation observed in early-type galaxies in the nearby Universe.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0bd23487800cb02466ee421b9c98d1e2182e5ebd

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Citations in the corpus

The current status of galaxy formation (2012, background): “Minor mergers provide an adequate gas supply to account for these (Kaviraj et al., 2009).”
The Evolution of Galaxy Structure Over Cosmic Time (2014, background): “…rate is high enough to provide this increase in sizes, with the most massive galaxies with M∗ > 10 11 M⊙ appearing to have enough minor mergers (e.g., Kaviraj et al. 2009) to produce this size evolution (Bluck et al. 2012), but this may not be the case for lower mass systems (e.g., Newman et al.…”
GALAXY ZOO: THE FUNDAMENTALLY DIFFERENT CO-EVOLUTION OF SUPERMASSIVE BLACK HOLES AND THEIR EARLY- AND LATE-TYPE HOST GALAXIES (2010, background): “Simulations of minor mergers between passive early-type galaxies and an ensemble of small gas-rich galaxies by Kaviraj et al. (2009) show that such events can produce the intermediate u − r colors exhibited by the late-type AGN hosts.”
Dissecting the size evolution of elliptical galaxies since z∼ 1: puffing-up versus minor-merging scenarios (2011, methodology): “The data analysed in this work together with the evidence collected in recent papers (e.g. Kaviraj et al. 2009; Shankar et al. 2010; Nierenberg et al. 2011) only leave the minor-merging scenario as a viable mechanism for the increase in the size of elliptical galaxies at least since z ∼ 1.”
THE RISE AND FALL OF PASSIVE DISK GALAXIES: MORPHOLOGICAL EVOLUTION ALONG THE RED SEQUENCE REVEALED BY COSMOS (2009, background): “…are understood to be a combination of recent arrivals to the red sequence (Ruhland et al. 2009), bulge-dominated systems experiencing triggered star formation after minor mergers (Kaviraj et al. 2009) or, at low masses, the formation of new disks in gas-rich environments (Kannappan et al. 2009).”
The SAURON project – XVII. Stellar population analysis of the absorption line strength maps of 48 early-type galaxies (2010, background): “Typically these disks represent only a minor mass fraction of the total galaxy mass (e.g., Crocker et al. 2009), but contain contributions of very young (∼ 100-300 Myr) stars (see also Kaviraj et al. 2009).”