A large population of ultra-compact dwarfs and bright intracluster globulars in the Fornax cluster

All the previously cataloged ultracompact dwarf (UCD) galaxies in the Fornax and Virgo clusters have 17.5 < b(J) < 20. Using the 2dF spectrograph on the Anglo-Australian Telescope, we have carried out a search for fainter UCDs in the Fornax Cluster. In the magnitude interval 19.5 < b(J) < 21.5, we have found 54 additional compact cluster members within a projected radius of 0 degrees.9 (320 kpc) of the cluster center, all of which meet our selection and observational criteria to be UCDs. These newly identified objects, however, overlap in luminosity and spatial distribution with objects classified as globular clusters (GCs) belonging to the central cluster galaxy NGC 1399; in fact, about half of the objects in our sample are included in recent catalogs of NGC 1399/Fornax GCs. The numbers, luminosity function, and spatial distributions of our compact object sample are consistent with being the bright tail of the Fornax cluster-wide GC population. Yet, our present larger sample of intergalactic compact objects forms a dynamically distinct population from both the NGC1399 GCs and the nucleated dwarf ellipticals in Fornax. This supports the interpretation that the UCDs, which populate the bright tail of the GC luminosity function, are, in some respects, a separate class of objects, at least to the extent that they have experienced a distinct dynamical history and origin, which differs from the bulk of the NGC1399 GCs. Correcting for our spectroscopic incompleteness, we estimate that there are similar to 105 +/- 13 of these brighter compact cluster objects down to b(J) < 21.5 in the central region of the Fornax, and hence these UCDs/globulars outnumber other galaxy types in this space. The differences in their dynamics and distribution compared to dwarf ellipticals (dEs) may be consistent with a threshing or tidal destruction origin, if they have come from a subpopulation of dE galaxies on initial orbits that rendered them susceptible to such processes

The spatial distribution and origin of the FUV excess in early-type galaxies

We present surface photometry of a sample of 52 galaxies from the GALEX and 2MASS data archives, these include 32 normal elliptical galaxies, 10 ellipticals with weak Liner or other nuclear activity, and 10 star forming ellipticals or early-type spirals. We examine the spatial distribution of the Far Ultra-Violet excess in these galaxies, and its correlation with dynamical and stellar population properties of the galaxies. From aperture photometry we find that all galaxies except for recent major remnants and galaxies with ongoing star formation show a positive gradient in the (FUV-NUV) colour determined from the GALEX images. The logarithmic gradient does not correlate with any stellar population parameter, but it does correlate with the central velocity dispersion. The strength of the excess on the other hand, correlates with both [alpha/Fe] and [Z/H], but more strongly with the former. We derive models of the underlying stellar population from the 2MASS H-band images, and the residual of the image from this model reveals a map of the centrally concentrated FUV excess. We examine a possible hypothesis for generating the FUV excess and the radial gradient in its strength, involving a helium abundance gradient set up early in the formation process of the galaxies. If this hypothesis is correct, the persistence of the gradients to the present day places a strong limit on the importance of dry mergers in the formation of ellipticals.Comment: 36 pages, accepted for publication in MNRAS. Appendices will appear in online journal only. This version has reduced resolution for the figure in Appendix B to comply with arXiv size limit

The HST/ACS Coma Cluster Survey. II. Data Description and Source Catalogs

The Coma cluster was the target of a HST-ACS Treasury program designed for deep imaging in the F475W and F814W passbands. Although our survey was interrupted by the ACS instrument failure in 2007, the partially completed survey still covers ~50% of the core high-density region in Coma. Observations were performed for 25 fields that extend over a wide range of cluster-centric radii (~1.75 Mpc) with a total coverage area of 274 arcmin^2. The majority of the fields are located near the core region of Coma (19/25 pointings) with six additional fields in the south-west region of the cluster. In this paper we present reprocessed images and SExtractor source catalogs for our survey fields, including a detailed description of the methodology used for object detection and photometry, the subtraction of bright galaxies to measure faint underlying objects, and the use of simulations to assess the photometric accuracy and completeness of our catalogs. We also use simulations to perform aperture corrections for the SExtractor Kron magnitudes based only on the measured source flux and half-light radius. We have performed photometry for ~73,000 unique objects; one-half of our detections are brighter than the 10-sigma point-source detection limit at F814W=25.8 mag (AB). The slight majority of objects (60%) are unresolved or only marginally resolved by ACS. We estimate that Coma members are 5-10% of all source detections, which consist of a large population of unresolved objects (primarily GCs but also UCDs) and a wide variety of extended galaxies from a cD galaxy to dwarf LSB galaxies. The red sequence of Coma member galaxies has a constant slope and dispersion across 9 magnitudes (-21<M_F814W<-13). The initial data release for the HST-ACS Coma Treasury program was made available to the public in 2008 August. The images and catalogs described in this study relate to our second data release.Comment: Accepted for publication in ApJS. A high-resolution version is available at http://archdev.stsci.edu/pub/hlsp/coma/release2/PaperII.pd

The Astropy Problem

The Astropy Project (http://astropy.org) is, in its own words, "a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages." For five years this project has been managed, written, and operated as a grassroots, self-organized, almost entirely volunteer effort while the software is used by the majority of the astronomical community. Despite this, the project has always been and remains to this day effectively unfunded. Further, contributors receive little or no formal recognition for creating and supporting what is now critical software. This paper explores the problem in detail, outlines possible solutions to correct this, and presents a few suggestions on how to address the sustainability of general purpose astronomical software

The ATLAS3D Project - XXIII. Angular momentum and nuclear surface brightness profiles

<p>Published Paper </p

Example HST image from the dataset

<p>Example HST image from the dataset.</p> <p>Galaxy: NGC474. Filter: F606W.</p

Angular momentum in core and core-less early-type galaxies

Abstract not available

Swinburne Metadata Stores Project

In this video Arna Karick and Ryan Wendt discuss ReDBox, a brand new, institution-wide solution facilitating the discovery, sharing, re-use, citation and management of research data collections