HUBBLE-SPACE-TELESCOPE DISCOVERY OF CANDIDATE YOUNG GLOBULAR-CLUSTERSIN THE MERGER REMNANT NGC-7252

Citation
Bc. Whitmore et al., HUBBLE-SPACE-TELESCOPE DISCOVERY OF CANDIDATE YOUNG GLOBULAR-CLUSTERSIN THE MERGER REMNANT NGC-7252, The Astronomical journal, 106(4), 1993, pp. 1354-1370
Citations number
50
Categorie Soggetti
Astronomy & Astrophysics
Journal title
ISSN journal
00046256
Volume
106
Issue
4
Year of publication
1993
Pages
1354 - 1370
Database
ISI
SICI code
0004-6256(1993)106:4<1354:HDOCYG>2.0.ZU;2-2
Abstract
New, high-resolution images of the central region of NGC 7252 obtained with the Planetary Camera of the Hubble Space Telescope are presented . NGC 7252 (sometimes referred to as the ''Atoms-for-Peace'' Galaxy) i s a prototypical example of a remnant of two merged disk galaxies. Our most striking result is the discovery of a population of about 40 blu e pointlike objects in this galaxy. The mean absolute magnitude of the se objects is M(V) = -13 mag; the mean color is V-I=0.7 mag; and the m ean effective radius is 10 pc (for H-1 = 50 km s-1 Mpc-1). The luminos ities, colors, projected spatial distribution, and sizes are all compa tible with the hypothesis that these objects formed within the last 1 Gyr following the collision of two spiral galaxies, and that they are young globular clusters. It therefore appears that the number of globu lar clusters may increase during the merger of gas-rich galaxies. This weakens van den Bergh's objection against ellipticals being formed th rough disk mergers, based mainly on the fact that disk galaxies have f ewer globular clusters per unit luminosity than ellipticals do. Other findings are: (1) NGC 7252 shows a single, semistellar nucleus; (2) re latively bright spiral structure is seen within 3''.5 (1.6 kpc) of the center, presumably formed through the continued infall of gas into a disk around the center of the galaxy; (3) dust lanes and very weak spi ral structure are seen out to about 9'' (4.2 kpc), primarily on the NE side; and (4) a ripple is found on the west side, 5''.0 from the cent er.