Search Publications
The Merger History, Active Galactic Nucleus, and Dwarf Galaxies of Hickson Compact Group 59
Hornschemeier, A. E.; Brandt, W. N.; Konstantopoulos, I. S. +16 more
Compact group galaxies often appear unaffected by their unusually dense environment. Closer examination can, however, reveal the subtle, cumulative effects of multiple galaxy interactions. Hickson Compact Group (HCG) 59 is an excellent example of this situation. We present a photometric study of this group in the optical (Hubble Space Telescope), …
Multiband Optical Observation of the P/2010 A2 Dust Tail
Hasegawa, Sunao; Usui, Fumihiko; Yoshida, Michitoshi +6 more
An inner main-belt asteroid, P/2010 A2, was discovered on 2010 January 6. Based on its orbital elements, it is considered that the asteroid belongs to the Flora collisional family, where S-type asteroids are common, while showing a comet-like dust tail. Although analysis of images taken by the Hubble Space Telescope and Rosetta spacecraft suggeste…
Discovery of the Host Cluster for the Fundamental Cepheid Calibrator Zeta Geminorum
Gieren, W.; Balam, D.; Lane, D. +2 more
New and existing CORAVEL, UBVJHKs , HST, HIP/Tycho, ARO, KPNO, and DAO observations imply that the fundamental Cepheid calibrator ζ Gem is a cluster member. The following parameters were inferred for ζ Gem from cluster membership and are tied to new spectral classifications (DAO) established for 26 nearby stars (e.g., HD53588/B7.5IV, HD…
An In-depth Study of the Abundance Pattern in the Hot Interstellar Medium in NGC 4649
Loewenstein, Michael; Davis, David S.
We present our X-ray imaging spectroscopic analysis of data from deep Suzaku and XMM-Newton Observatory exposures of the Virgo Cluster elliptical galaxy NGC 4649 (M60), focusing on the abundance pattern in the hot interstellar medium (ISM). All measured elements show a radial decline in abundance, with the possible exception of O. We construct ste…
The Size Difference between Red and Blue Globular Clusters is not due to Projection Effects
Sills, Alison; Harris, William E.; Webb, Jeremy J.
Metal-rich (red) globular clusters in massive galaxies are, on average, smaller than metal-poor (blue) globular clusters. One of the possible explanations for this phenomenon is that the two populations of clusters have different spatial distributions. We test this idea by comparing clusters observed in unusually deep, high signal-to-noise images …
A Nearby Analog of z ~ 2 Compact Quiescent Galaxies with a Rotating Disk
Franx, Marijn; van Dokkum, Pieter; Bezanson, Rachel +1 more
Recent studies have identified a population of compact quiescent galaxies at z ~ 2. These galaxies are very rare today and establishing the existence of a nearby analog could allow us to study its structure in greater detail than is possible at high redshift. Here we present such a local analog, NGC 5845, which has a dynamical mass of M dyn
Ionized Gas in the First 10 kpc of the Interstellar Galactic Halo: Metal Ion Fractions
Howk, J. Christopher; Consiglio, S. Michelle
We present direct measures of the ionization fractions of several sulfur ions in the Galactic warm ionized medium (WIM). We obtained high-resolution ultraviolet absorption-line spectroscopy of post-asymptotic giant branch stars in the globular clusters Messier 3 [(l, b) = (42fdg2, +78fdg7), d = 10.2 kpc, and z = 10.0 kpc] and Messier 5 [(l, b) = (…
Solar-cycle Variation of Sound Speed near the Solar Surface
Rabello-Soares, M. C.
We present evidence that the sound-speed variation with solar activity has a two-layer configuration, similar to the one observed below an active region, which consists of a negative layer near the solar surface and a positive one in the layer immediately below the first one. Frequency differences between the activity minimum and maximum of solar …
Cassini VIMS Observations Show Ethane is Present in Titan's Rainfall
Nicholson, Philip D.; Sotin, Christophe; Barnes, Jason W. +6 more
Observations obtained over two years by the Cassini Imaging Science Subsystem suggest that rain showers fall on the surface. Using measurements obtained by the Visual Infrared Mapping Spectrometer, we identify the main component of the rain to be ethane, with methane as an additional component. We observe five or six probable rainfall events, at l…
Ongoing Massive Star Formation in NGC 604
Groves, B.; Brandl, B.; Hunter, D. +1 more
NGC 604 is the second most massive H II region in the Local Group, thus an important laboratory for massive star formation. Using a combination of observational and analytical tools that include Spitzer spectroscopy, Herschel photometry, Chandra imaging, and Bayesian spectral energy distribution fitting, we investigate the physical conditions in N…