EUROVO FC

AVO
SWG
Management
Science
Standards
Technology
Reports&Minutes
Forum
Events
Contacts
Help

EGG

Main

Know

Test

TWiki

AVO Demo 2005: Galaxies Science Case

Background

The prime case selected after analysis of the SWG suggestions is the 'Star Formation Histories in Galaxies' case.

This involves retrieving multiwavelength datasets to enable galaxy spectral energy distributions (SEDs) to be generated. These are then compared against stellar spectral evolution codes, to enable information to be derived on galaxy star formation histories.

A good survey for our purposes is the European Large-Area ISO Survey (ELAIS), which covers five different areas (N1, N2, N3, S1, and S2) over ~ 10 sq. deg.

Descriptive Workflow

• 1. Starting point: ELAIS Final band-merged Catalogue retrieval from VizieR - via a registry query. This catalogue contains multifrequency data for all 3,762 ELAIS sources, namely: 20 cm radio fluxes, 175, 90, 15, 6.7 micron (ISO) fluxes, J, H, K (mostly 2MASS) magnitudes, U, g', r', i', Z (INT Wide Field Survey) magnitudes, spectroscopic and photometric redshifts. X-ray (Chandra) data are also available (see below).
  • this requires a query of the ELAIS catalogue, select * to return the whole catalogue to Myspace. The groovy script then runs on this file.

• 2. Prepare file for SED building in MySpace using scripts
  • 2.1 Conversion of catalog magnitudes and fluxes into consistent units using appropriate zero points
  • 2.2 Conversion of band names into effective frequency and bandwidth
  • 2.3 Put SED info into the correct format for Specview, which now can read VOTables. These intermediate steps are necessary because the various components still do not "speak" a common language.

• 3. Object Selection: e.g., based on availability of spectroscopic redshifts, as we want to evaluate, for example, galaxy ages. We will select the "red" and "blue" galaxies, to show their very different SEDs and model best-fits. We will start by showing some examples of, say, a few SEDs, together with some template spectra from Kinney et al. Issue of copying these to MySpace.

• 4. Display SED in Specview. The SEDs for ELAIS sources can be put into Specview compatible format within MySpace.

• 5. Generate Model SEDs using web services (applications listed below). Worflow will have to make sure that the output format is compatible with Specview (e.g., VOTable).

• 6. Data-Model comparisons by overplotting in the SED tool. Specview has been modified to allow easy re-normalization of models to observed SED by simply dragging the model spectrum. Initial plans involved finding the best fit solution but we might instead show a few examples of fits, and produce before hand a grid of models.

• 7. Based on results of model comparisons, select objects, generate multi-wavelength image cutouts and display. Image data could include: WFS, Spitzer, ISO, 2MASS, the latter two available also via the Aladin image server. All Spitzer images have been downloaded from the archive and are available through the prototype.

• A preliminary top level workflow shows some of the processes involved.
• A preliminary workflow with standards and data noted.

• See ElaisSeds for notes on flux conversion and making SED files

• Need to make flow chart for demo.

Data

Key datasets for this scenario include (bold face indicate essential datasets, italics indicate under review):

Local Universe

SINGS: Spitzer Infrared Nearby Galaxies Survey

• STScI Pages

Distant Universe

ELAIS: European Large-Area ISO Survey

• Imperial College page; final band-merged catalogue available here, MNRAS paper available here. The table description in the paper is not detailed enough to accurately specify each column (some labels refer to multiple columns). One can use the metadata description here

• A preliminary VOTable version of this Elais catalog is available here elaiscatf_21a.vot.

• Here is an earlier version on catalog (elascatf_16a) in the IPAC catalog server

• WFS INT data
• 2MASS:
  • http://www.ipac.caltech.edu/2mass/overview/access.html
  • Aladin image server

• ISO data: available via SIA ?
• X-ray images and catalogues for the N1 and N2 regions

SWIRE: Spitzer Wide-area Infrared Extragalactic Survey

• IPAC
• SWIRE Ancillary Data Atlas This gives links to INT-WSF data in MEFS format; see WFS INT data for single-image FITS files.

more on data collections ...

SwireSiapTests

Applications

• Link to AVO Prototype - SWG Download Page
• Catalogue generation
  • SWarp: http://terapix.iap.fr/rubrique.php?id_rubrique=49
  • SExtractor: http://terapix.iap.fr/rubrique.php?id_rubrique=91/
  • Xmatch tool: at CDS

• Spectral Synthesis Codes:
  • Pegase: http://www2.iap.fr/users/fioc/PEGASE.html
    • web access: http://leda.univ-lyon1.fr/ (see 'Compute Evolutive Template Spectra with PEGASE' link)
  • Starburst99: http://www.stsci.edu/science/starburst99/
    • web access at http://www.stsci.edu/science/starburst99/model/parameters.html
  • Galaxev: http://www.cida.ve/~bruzual/bc2003
  • Galaxev: single tar file available at http://www.eso.org/~prosati/avo/bc03.tar.gz

• Spectral plotting (SED visualisation):
  • Specview: http://www.stsci.edu/resources/software_hardware/specview
  • VOSpec: Java tool
• Model/Data visualisation:
  • Mirage: http://cm.bell-labs.com/who/tkh/mirage/index.html
    • VO enabled Mirage: http://skyservice.pha.jhu.edu/develop/vo/mirage/

• See also AppsForDemo05.

Applications for redshift determination (20040906: optional)

• Photometric:
  • Hyperz
  • Bpz
  • ANNz

• Principal Component Analysis (PCA) - to determine galaxy redshift
  • Madgwick, D. et al, 2002
  • Folkes, S, et al, 1999

Flux conversions

This page gives a detailed description of Photometric Flux Calibration for the SDSS DR3 (based on the AB system)

This page http://dls.bell-labs.com/calib/vegaab.html describes the conversion of Vega to AB mags

This page http://www.stsci.edu/instruments/wfpc2/Wfpc2_dhb/wfpc2_ch52.html describes photometric zeropoints for WFPC2.

Attachment Action Size Date Uploaded by Comment templates.tar manage 623.0 K 19 Jan 2005 - 15:20 MarkAllen kinney calzetti templates