arXiv subjects

Susan A. Kassin

Publications and source records attributed to Susan A. Kassin.

39 records · Page 3Linked to original sources

arXiv2006

Dark and Baryonic Matter in Bright Spiral Galaxies: I.Near-infrared and Optical Broadband Surface Photometry of 30 Galaxies

We present photometrically calibrated images and surface photometry in the B, V, R, J, H, and K-bands of 25, and in the g, r, and K-bands of 5 nearby bright (Bo_T<12.5 mag) spiral galaxies with inclinations between 30-65 degrees spanning the Hubble Sequence from Sa to Scd. Data are from The Ohio State University Bright Spiral Galaxy Survey, the Two Micron All Sky Survey, and the Sloan Digital Sky Survey Second Data Release. Radial surface brightness profiles are extracted, and integrated magnitudes are measured from the profiles. Axis ratios, position angles, and scale lengths are measured from the near-infrared images. A 1-dimensional bulge/disk decomposition is performed on the near-infrared images of galaxies with a non-negligible bulge component, and an exponential disk is fit to the radial surface brightness profiles of the remaining galaxies.

astro-ph↗

arXiv2006

Dark and Baryonic Matter in Bright Spiral Galaxies: II. Radial Distributions for 34 Galaxies

We decompose the rotation curves of 34 bright spiral galaxies into baryonic and dark matter components. Stellar mass profiles are created by applying color-M/L relations to near-infrared and optical photometry. We find that the radial profile of the baryonic-to-dark-matter ratio is self-similar for all galaxies, when scaled to the radius where the contribution of the baryonic mass to the rotation curve equals that of the dark matter (R_X). We argue that this is due to the quasi-exponential nature of disks and rotation curves that are nearly flat after an initial rise. The radius R_X is found to correlate most strongly with baryonic rotation speed, such that galaxies with R_X measurements that lie further out in their disks rotate faster. This quantity also correlates very strongly with stellar mass, Hubble type, and observed rotation speed; B-band central surface brightness is less related to R_X than these other galaxy properties. Most of the galaxies in our sample appear to be close to maximal disk. For these galaxies, we find that maximum observed rotation speeds are tightly correlated with maximum rotation speeds predicted from the baryon distributions, such that one can create a Tully-Fisher relation based on surface photometry and redshifts alone. Finally, we compare our data to the NFW parameterization for dark matter profiles with and without including adiabatic contraction as it is most commonly implemented. Fits are generally poor, and all but 2 galaxies are better fit if adiabatic contraction is not performed. In order to have better fits, and especially to accommodate adiabatic contraction, baryons would need to contribute very little to the total mass in the inner parts of galaxies, seemingly in contrast with other observational constraints.

astro-ph↗

arXiv2003

Stellar Populations in NGC 4038/39 (The Antennae): Exploring A Galaxy Merger Pixel-by-Pixel

We present deep, photometrically calibrated BVRJHK images of the nearby interacting galaxy pair NGC 4038/39 (``The Antennae''). Color maps of the images are derived, and those using the B, V, and K-bands are analyzed with techniques developed for examining the colors of stars. From these data we derive pixel-by-pixel maps of the distributions of stellar populations and dust extinction for the galaxies. Analysis of the stellar population map reveals two distinct episodes of recent star formation: one currently in progress and a second that occurred ~600 Myr ago. A roughly 15 Gyr-old population is found which traces the old disks of the galaxies and the bulge of NGC 4038. The models used successfully reproduce the locations of clusters, and the ages we derive are consistent with those found from previous Hubble Space Telescope observations of individual star clusters. We also find 5 luminous ``super star clusters'' in our K-band images that do not appear in the B or V-band images. These clusters are located in the overlap region between the two galaxies, and are hidden by dust with visual extinctions of A_V ~> 3 mag. The techniques we describe in this paper should be generally applicable to the study of stellar populations in galaxies for which detailed spatial resolution with Hubble is not possible.

astro-ph↗