Birmingham/Warwick Workshop - Group A - Extra Galactic

Participants

LouisaNolan, JesperRasmussen, Paul Russell, Abdul Alshino, TrevorPonman, AlastairSanderson, Graham Smith, Nazirah Jetha, Nathan Slack, WalterDelPozzo, VictoriaHamiltonmorris, JonathanTedds, NicholasWalton

Possible extragalactic AstroGrid projects:

A. Galaxy cluster profiles (Alastair)

1. Select sample of galaxies by cross-correlating X-ray cluster list with Astrogrid galaxy catalogues
2. Pull out lists of galaxies for each cluster & plot colour-mag diagrams
3. Identify red sequence, then extract RS galaxies & plot surface density profile to provide an essentially background-free cluster galaxy profile
4. Fit various parametrisations to galaxy number density profile and also luminosity-weighted galaxy profile; compare to rho_gas(r) & M(r)
5. Extract other information on the galaxies where available, e.g. star formation status from spectral analysis, radio properties etc., maybe also including galaxy redshifts to look at the velocity dispersion profile

B. Galaxy properties vs environment (Louisa)

1. investigating environment:
   • projected density
   • 3D density
   • membership of groups / clusters / filaments
   • (how) would it work for objects not part of a large survey?
2. morphological classification esp. identifying early-types (images & spectra?), star-forming and E+A galaxies (spectra?).
3. cross-correlating the above with HI and X-ray observations.

C. Galaxy properties (Somak)

Given a list of galaxies compiled from an opticall survey with RA, Dec and some other optical property (e.g. diameter), I would like to cross-correlate with the 2MASS near-IR catalogue, and the ZCAT redshift survey, to merge the three, to find redshifts and near-IR magnitudes for galaxies in my original catalogue.

D. Supercluster redshifts (Somak)

Given a target supercluster at RA= 23:43:39.6 Dec +00:19:40.3, I would like to extract all SDSS galaxies within a radius of 10 degrees, use ANNz to find approx redshifts of each and plot the 3D distribution of all galaxies with a photo-z in the range z=0.2-0.3 in this sample.

E. Stripping of galaxies in groups (Trevor/Jesper)

Look for a correlation between HI, spectral and environmental properties of galaxies which is expected if starbursting galaxies can be stripped of their ICM within groups.

1. Find galaxies with starburst or post-starburst features
2. Find galaxy morphology and magnitude to estimate expected HI content
3. Use information from radio surveys (e.g. HIPASS) to estimate actual HI content - hence HI-deficiency
4. Establish galaxy environment from both local galaxy density, and from presence of diffuse X-ray emission (e.g. from RASS). Exclude galaxies in rich clusters.
5. Evaluate significance of any correlation seen between HI-deficiency and environment, for post-starbursts.
6. Do the same for galaxies without post-starburst features, as a control.

Problem Description

B: Galaxy properties vs environment

Plot the positions of E+A galaxies in a cluster, and compare properties of E+A galaxies with 'normal' galaxies (colour-magnitude). Find X-ray data for the cluster - Louisa & Al

Workshop solution

B: Galaxy properties vs environment

Use catalogue of E+As listed in the registry, cross-reference with SDSS DR4 and X-ray archives.

1. tried using Astroscope to find catalogues with cluster data; plot RA and dec, g-r / r, using Topcat:
   • Astroscope quite slow - works well for small data sets, but had problems with it crashing / being slow for larger data sets
   • it would be nice to be able to choose which catalogues to search before searching
   • loading data into Topcat and Aladin
2. tried workflow using canned cone search:
   • a simpler way to select catalogues would help
   • how to turn ascii tables into VOTables?
     • Can do it in Topcat - JAT has now written simple howto doc
     • make simple template VOTable available to users
   • could turn it into a workflow to extract all data in region from selected catalogues not just those objects which are in all the catalogues
3. ADQL
   • very much like the easy column selection in ADQL
4. General notes:
   • a simple method of cross-matching multiple catalogues is necessary
   • everything is slow, and falls over too much, which is off-putting
   • better progress reporting required throughout system
   • better handling of catalogues e.g. searching for relevant catalogues, selecting catalogues without cut and paste from the registry
   • insufficient information re what is available for given found resource
   • ability to filter general resource search results needed
   • will be extremely useful with more practice and improvements!
   • email announce list for registered users for major new workbench releases including new functionality and changes.

-- LouisaNolan - 11 Oct 2006