ALFALFA Graduate Student Project

Proposal Title: HI Survey of the Southern extent of the Virgo Cluster
Student Name: Brian R. Kent
Advisor: Riccardo Giovanelli
Context: one part of Ph.D. Thesis
Institution: Cornell University
Time frame: until Spring 2006, followups beyond
Other collaborators: Noah Brosch, Martha Haynes, Lyle Hofmann, Amelie Saintonge, Sabrina Stierwalt
Publication expected? yes


    The Virgo cluster and its surrounding environment on the sky provide an excellent region to focus on for the HI ALFALFA Survey. ALFALFA is committed to deliver high elvel data to the community in a timely manner, that includes the production of gridded data cubes and source catalogs. The Virgo cluster region is one of the most studied, within the ALFALFA sky coverage. We intend to provide advanced data products of the part of the cluster covered in the Spring 2005 observing season. The nearest large cluster has an overdensity of galaxies, as well as well documented catalogs for followup and comparison (Virgo Cluster Catalog, SDSS DR4, etc.)

L-band drift scans have been recorded in the Southern extent of the Virgo cluster. A detailed inspection of the sky coverage will be made with the POSFIND procedure of the 206 drift files covering 60 square degrees of the sky. All data will be run through both a 2-D source extractor, from which we expect more than 2000 possible detections down to a SN ~3.5, and through a 3-D source extractor, which should deliver nearly twice as many sources. The cross-correlation of both source catalogs will allow us to test the validity of pre-survey simulations. Automated scripts will cut out spectral images, 1-D spectra, and retrieved 5' SDSS DR4 images. The software to handle those tasks is currently being tested, including an interface, which allows the user to quickly analyze the catalog with SDSS D4 and DSS2 Blue images and spectra - false detections can be scrutinized and removed from the catalog. Detailed statistics about the region and thorough cross correlations will be generated. Various tools in IDL are being developed concurrently to manipulate these datasets. Final source catalogs will be extracted from gridded datacubes, with integrated fluxes and velocity widths.

    Interesting sources will be extracted with plans for L-band/C-configuration VLA follow ups. Science goals will include (but are not limited to) sub-structure in the Virgo cluster, dynamics of these sub-groups, and the implications "dark" hydrogen galaxies might have on the group environments. The catalog obtained will allow for a study of distribution of HI bearing systems in the cluster and to make an initial determination of the HI mass function; this analysis will follow immediately after the preparation of the catalog.

ALFALFA region: RA: 12.0 to 13.0 hours. Dec: 9 to 13 degrees
ALFALFA data to be used: raw data, Level I data, ALFALFA Catalog
Other data sets to be used: Public Domain datasets available at, SDSS DR4, VCC/NOG/BGC catalogs
Products to be delivered: Self contained database as well as useful contributions to final ALFALFA databases, final gridded data cubes. POSFIND, IDL tools to cross-correlate source catalogs with other data sources; NVO-compatible software for robust public access. Cube and gridded data visualization utilities.


Software DevelopmentIDL/Web code Throughout projectIn Progress
Team assemblytask assignment, delegation Sept2005Done
Level I datacompletion of data processing Sept2005First round done, calibration needed
Level II datagridded, baselined, cleaned catalog Oct2005 In Progress
Status reviewnext report of progress February 2005  
Catalog releasecross-referenced catalog February 2006  
First paper outsubmission for publication Spring 2006  
Followup 21cm obsVLA observations of notable sources, C array Submit March 2006 Fall 2006

October 10, 2005 by bkent