NICMOS Observations of Low-Redshift Quasar Host Galaxies

We have obtained Near-Infrared Camera and Multi-Object Spectrometer images of 16 radio quiet quasars observed as part of a project to investigate the ``luminosity/host-mass limit.'' The limit results were presented in McLeod, Rieke, & Storrie-Lombardi (1999). In this paper, we present the images themselves, along with 1- and 2-dimensional analyses of the host galaxy properties. We find that our model-independent 1D technique is reliable for use on ground-based data at low redshifts; that many radio-quiet quasars live in deVaucouleurs-law hosts, although some of the techniques used to determine host type are questionable; that complex structure is found in many of the hosts, but that there are some hosts that are very smooth and symmetric; and that the nuclei radiate at ~2-20% of the Eddington rate based on the assumption that all galaxies have central black holes with a constant mass fraction of 0.6%. Despite targeting hard-to-resolve hosts, we have failed to find any that imply super-Eddington accretion rates.Comment: To appear in ApJ, 28 pages including degraded figures. Download the paper with full-resolutio figures from http://www.astro.wellesley.edu/kmcleod/mm.p

On the Rotation Period of (90377) Sedna

We present precise, ~1%, r-band relative photometry of the unusual solar system object (90377) Sedna. Our data consist of 143 data points taken over eight nights in October 2004 and January 2005. The RMS variability over the longest contiguous stretch of five nights of data spanning nine days is only 1.3%. This subset of data alone constrain the amplitude of any long-period variations with period P to be A<1% (P/20 days)^2. Over the course of any given 5-hour segment, the data exhibits significant linear trends not seen in a comparison star of similar magnitude, and in a few cases these segments show clear evidence for curvature at the level of a few millimagnitudes per hour^2. These properties imply that the rotation period of Sedna is O(10 hours), cannot be 10 days, unless the intrinsic light curve has significant and comparable power on multiple timescales, which is unlikely. A sinusoidal fit yields a period of P=(10.273 +/- 0.002) hours and semi-amplitude of A=(1.1 +/- 0.1)%. There are additional acceptable fits with flanking periods separated by ~3 minutes, as well as another class of fits with P ~ 18 hours, although these later fits appear less viable based on visual inspection. Our results indicate that the period of Sedna is likely consistent with typical rotation periods of solar system objects, thus obviating the need for a massive companion to slow its rotation.Comment: 7 pages, 4 figures, 2.5 tables. Final ApJL version, minor changes. Full light curve data in tex

Unicyclic Components in Random Graphs

The distribution of unicyclic components in a random graph is obtained analytically. The number of unicyclic components of a given size approaches a self-similar form in the vicinity of the gelation transition. At the gelation point, this distribution decays algebraically, U_k ~ 1/(4k) for k>>1. As a result, the total number of unicyclic components grows logarithmically with the system size.Comment: 4 pages, 2 figure