Spatially Correlated Cluster Populations in the Outer Disk of NGC 3184
Abstract
We use deep (~27.5 mag V-band point-source limiting magnitude) V- and U-band Large Binocular Telescope imaging to study the outer disk (beyond the optical radius R 25) of the non-interacting, face-on spiral galaxy NGC 3184 (D = 11.1 Mpc; R 25 = 11.1 kpc) and find that this outer disk contains >1000 objects (or marginally resolved "knots") resembling star clusters with masses ~102-104 M sun and ages up to ~1 Gyr. We find statistically significant numbers of these cluster-like knots extending to ~1.4 R 25, with the redder knots outnumbering bluer at the largest radii. We measure clustering among knots and find significant correlation to galactocentric radii of 1.5 R 25 for knot separations <1 kpc. The effective integrated surface brightness of this outer disk cluster population ranges from 30-32 mag arcsec-2 in V. We compare the H I extent to that of the correlated knots and find that the clusters extend at least to the damped Lyman-α threshold of H I column density (2 × 1020 cm-2; ~1.62 R 25). The blue knots are correlated with H I spiral structure to ~1.5 R 25, while the red knots may be correlated with the outer fringes of the H I disk to ~1.7 R 25. These results suggest that outer disks are well populated, common, and long-lasting features of many nearby disk galaxies.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2009
- DOI:
- 10.1088/0004-637X/700/2/1977
- arXiv:
- arXiv:0906.1211
- Bibcode:
- 2009ApJ...700.1977H
- Keywords:
-
- galaxies: individual: NGC 3184;
- galaxies: star clusters;
- galaxies: structure;
- methods: statistical;
- Astrophysics - Cosmology and Extragalactic Astrophysics
- E-Print:
- Accepted for publication in The Astrophysical Journal. 12 pages, 10 figures