PhD Thesis (PDF) - Department of Astronomy - University of Virginia

y an amount that is consistent with our positional uncertainty, while in NGC 4382,
the centroid is off by 3 times our positional uncertainty. It is unclear whether
either of these sources is an AGN in the galaxy center or an LMXB projected near
the center. We also examined hard-band (2–10 keV) images of both galaxies in which
AGNs might be more obvious, particularly as the diffuse emission from the galaxies is
soft. We did not see any new sources near the center, nor were either of the centermost
sources particularly hard. Thus, we have no unambiguous evidence for AGNs in these
galaxies. Conservatively, we adopt the luminosity of the centermost source in each
galaxy (1.5 × 10 38 ergs s −1 in NGC 4365 and 9.0 × 10 37 ergs s −1 in NGC 4382) as the
upper limit to the central AGN luminosity.
We examined NGC 4382 for a source associated with SN 1960r. Source 27 is
the closest detected source; however, it is ∼20 ′′ from the Porter (1993) position. We
placed a 2. ′′ 0 radius circular aperture, similar to that of source 27 plus 0. ′′ 5 to account
for our positional uncertainty, and a 4. ′′ 0 radius circular aperture to determine the
local background. No net counts were detected, and we can place a 3 σ upper limit
of 6.3 × 10 37 ergs s −1 .
For NGC 4365, A. Kundu kindly provided a list of 325 globular cluster positions
from data presented in Kundu & Whitmore (2001). The WFPC2 field of view overlaps
37 X-ray point sources from Table 2.1. After solving for a small offset, 18 of the 37
sources have a globular cluster within 1. ′′ 02. The expected number of associations
from random positions is ∼0.6 based on the density of the globular clusters. This
number is consistent with Kundu et al. (2003), who adopted less strict source detection
criteria. Recently Larsen et al. (2003) published a short list of globular clusters with
spectroscopy. In addition to globular clusters identifications from Kundu & Whitmore
(2001), globular cluster 1 from Larsen et al. (2003) agrees with the position of our
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