The late stellar assembly of massive cluster galaxies via major merging

Kim Vy H Tran, John Moustakas, Anthony H. Gonzalez, Lei Bai, Dennis F Zaritsky, Stefan J. Kautsch

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

We present multiwavelength observations of the brightest galaxies in four X-ray-luminous groups at z-0.37 that will merge to form a cluster comparable in mass to Coma. Ordered by increasing stellar mass, the four brightest group galaxies (BGGs) present a time sequence where BGG-1, 2, and 3 are in merging systems and BGG-4 is a massive remnant (M* p 6.7 x 10 11 M⊙). BGG-1 and 2 have bright, gravitationally bound companions and BGG-3 has two nuclei separated by only 2.5 kpc; thus, merging atz < 0.5 increases the BGG mass by ⊙40% (t MGR < 2 Gyr) and V-band luminosity by-0.4 mag. The BGGs' rest-frame (B-V) colors correspond to stellar ages of >3 Gyr, and their tight scatter in (B-V) color (σBV=0.032) confirms that they formed the bulk of their stars at z > 0.9. Optical spectroscopy shows no signs of recent (<1.5 Gyr) or ongoing star formation. Only two BGGs are weakly detected at 24 μm, and X-ray and optical data indicate that the emission in BGG-2 is due to an AGN. All four BGGs and their companions are early-type (bulge-dominated) galaxies, and they are embedded in diffuse stellar envelopes up to-140 kpc across. The four BGG systems must evolve into the massive, red, early-type galaxies dominating local clusters. Our results show that (1) massive galaxies in groups and clusters form via dissipationless merging and (2) the group environment is critical for this process.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume683
Issue number1 PART 2
DOIs
StatePublished - 2008

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galactic clusters
assembly
galaxies
spectroscopy
stellar envelopes
coma
stellar mass
star formation
x rays
color
stars
nuclei

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Tran, K. V. H., Moustakas, J., Gonzalez, A. H., Bai, L., Zaritsky, D. F., & Kautsch, S. J. (2008). The late stellar assembly of massive cluster galaxies via major merging. Astrophysical Journal, 683(1 PART 2). https://doi.org/10.1086/591422

The late stellar assembly of massive cluster galaxies via major merging. / Tran, Kim Vy H; Moustakas, John; Gonzalez, Anthony H.; Bai, Lei; Zaritsky, Dennis F; Kautsch, Stefan J.

In: Astrophysical Journal, Vol. 683, No. 1 PART 2, 2008.

Research output: Contribution to journalArticle

Tran, KVH, Moustakas, J, Gonzalez, AH, Bai, L, Zaritsky, DF & Kautsch, SJ 2008, 'The late stellar assembly of massive cluster galaxies via major merging', Astrophysical Journal, vol. 683, no. 1 PART 2. https://doi.org/10.1086/591422
Tran, Kim Vy H ; Moustakas, John ; Gonzalez, Anthony H. ; Bai, Lei ; Zaritsky, Dennis F ; Kautsch, Stefan J. / The late stellar assembly of massive cluster galaxies via major merging. In: Astrophysical Journal. 2008 ; Vol. 683, No. 1 PART 2.
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