Votc Science in Stage Two (Oct 2005 - Mar 2006)

Galactic Case I : IMF in massive stars

please note some links are to tools/data under development, not for unqualified broadcasting!

Background

The Initial Mass Function (IMF) of the bright end of the mass scale is a crucial parameter for determining the upper limit of mass and its connection to the environment such as metallicity. In order to determine the IMF, it is necessary to know the mass of the stars (as inferred from their position in the colour-magnitude diagram) and their absolute magnitude (i.e. distance). While the distance is not difficult to determine in extragalactic systems, for our own Galaxy the best way is to consider stellar associations, where distance and extinction is found for all stars in each system. High-mass star forming regions are identified by the presence of UCHII (ultra-compact HII) regions, molecular and spectral diagnostics such as the signature of hot dust. Very massive stars evolve so fast that supernovae and their rapidly-expanding remnants (SNR) are also indicators of violent starburst activity, especially in distant and obscured galaxies. For more detail see the original case from the AVO SRM.

Required Data and Applications

• Identification based on IR-optical-UV stellar characteristics
  • Archives in the optical of very young star clusters, superclusters and associations (MW, LMC, SMC, M31)
  • UV spectra of massive stars for population synthesis (from VLT-UVES, HST, IUE).
  • Tools which use the UV spectra and the stellar evolution codes to determine the IMF and dependency with metallicity.
    • Starburst99
    • CMFGen, which generates large (5E+08 points) synthetic spectra and associated properties - T, G etc. e.g. output SEDs and Martins et al. A&A 2005
    • Spectral fitting - equivalent widths etc.
  • IR e.g. UKIDSS, Spitzer data for red supergiants.
• Massive star formation
  • UV-optical-IR-mm data as above plus JCMT etc.
    • MOCASSIN produces model SEDs for galactic nebulae - preparing to wrap as AstroGrid tool.
  • Radio catalogues
    • Cross-ID data at different resolutions and select UCHII regions, SNR etc. by spectral index using SpecFiind (development continuing under VOTech).
  • Radio imaging - various published surveys, CORNISH (Co-Ordinated Radio 'N' Infrared Survey for High-mass Star formation) using the VLA with common coverage with GLIMPSE, UKIDSS, BU-FCRAO Galactic Ring Survey - committed to making the data available to VOs.
    • Morphological tools needed
  • Radio datacubes/spectra
    • Some progress towards enabling VO access - VOSpec, CGPS/Aladin prototype, RadioNet work etc.
• General requirements
  • Access to supporting data from any available VO-enabled sources including SIMBAD and Vizier
  • Registration and cross-identification in crowded fields
    • Anything similar to SpecFiind for other wavelengths?
  • Extension/automation of VOSpec-like functions
    • Aperture matching, coordinate conversion, photometric conversions for constructing SEDs
    • Shifting composite spectra to the rest wavelengths of given lines, measuring line widths etc.
  • STILTS/TopCat - tools for converting IPAC format tables (e.g. Spitzer source lists) to VOTable under development.
  • Fitting models to SEDs - how to determine the best fit? How to automate? UCL tool huntfit3 minimises chi-sq to see which of a family of models matches the data, designed to work on SEDs with tens-hundreds of points, investigating possible VO use.
  • Use of teaching sets etc. in the above - AstroNeural?
  • Data sets can be massive - optimise locating/moving generation of models and observed data etc.

VO Workflow

• Identify candidate Gould Belt regions (see AstroGrid Gould Belt ) e.g. covered by Spitzer C2D survey and obtain observational data
  • Select data from standard IR catalogues (via Vizier etc.) covering regions
    • Pre-select using IR version of ColourCutter
  • Convert Spitzer catalogues to VOTable (STILTS)
  • Possibly select other data
  • Cross-match
    • If possible, apply aperture corrections
  • Convert all data to physical units and construct SEDs (VOSpec?)
• Use Mocassin to construct SEDs for hot stars with nebulae
• Select observed SEDs fitting models
• Extend the investigation when new data are available.

A schematic workflow is attatched.

End Results

• See Gould Belt case
• IMF at high mass end in different areas of Galaxy, as a function of metallicity (variations just starting to emerge e.g. in Westerlund 1
• IMF in nearby galaxies of varying metallicity.
• IMF for high redshift galaxies? At present the Radio/IR relationship, which holds out to high redshift, seems a very good indicator of massive star formation, but how reliably is this extrapolated to the whole IMF?

ExtraGalactic Case I : Clustering of clusters (of galaxies)

Background

The formation and evolution of clusters of galaxies is an important key to understand the formation of large scale structure, the formation and evolution of galaxies, the reionization of the Universe and the origions of the metallicities in the intergalactic medium.

The abundance of clusters beyond z=1 will be a field of intense activity over the next years. Much of the emphasis will be on X-ray surveys with XMM (e.g. Romer et al., 2001), and the emerging field of Sunyaev-Zeldovich (SZ) survey astronomy (Holder et al., 2000). These surveys will cover large areas, tens of square degrees, and target redshifts beyond z=1.

Required Data and Applications

WFCAM (IR) + SDSS (Opt) + XMM (Xray) + Spitzer (mid- & far-IR)

Status of XMM-Mewton programs aiming at large scale structure studies:

COSMOS

• 26 observations performed so far among them:
  • 6 are public
  • 13 will be public before March 2006
  • 7 will be public after March 2006
• Some work done on clustering of clusters (Finoguenov et al. 2005), and AGN (Miyaji et al. 2006). Nothing published on a refereed journal yet.
• Only the 1.4 Ghz catalogue for a pilot project is available (J/AJ/128/1974). Images in several bands - X-rays included - are available

XMM-Newton Large Scale Survey (LSS)

• 29 public observations
• catalogue of X-ray sources in the central 1 squared degree published in Vizier (J/A+A/439/413/xmds1) - Paper published in Astronomy & Astrophysics (Chiappetti et al. 2005)
• 12 spectroscopically identified clusters at z<0.6 published by Willis et al. 2006. The catalogue of a larger and complete sample of clusters is still to come.
• catalogue of spectroscopically identified AGN expected to to published on longer timescales
• [members of the LSS Consortium at ESAC]
• Spitzer data already available.

Others:

Southern Abell Redshift Survey (local universe comparison)

• Paper with catalogue of spectroscopy of 3440 galaxies in 39 galaxy clusters.

Applications

• SWARP, Sextractor, Cross Match, R, VisIVO, Aladin
• Cluster finding algorithm (Astroneural?)
• Tools to calculate angular correlation function of the selected sources/clusters, inversion (VisIVO)
• Need some theoretical simulations tools (or use the datasets already available from e.g. White et al).

VO Workflow

• Find areas of sky covered by SDSS and Spitzer.
• For each of those retrieve the catalogues of objects from their catalogue servers or download the catalogues.
• Cross match the catalogues.
• Determine photometric redshifts.
• Generate a mask file from the coverage of the surveys, taking into account bad regions, areas not covered by both surveys, etc. (e.g. using Mangle (http://casa.colorado.edu/~ajsh/mangle)).
• Generate a random catalogue (positions and redshifts).
• Apply the mask to object and random catalogue.
• Now do different selection of objects, e.g. EROs, blue objects, QSOs, ...
• Do a second selection on redshift or/and luminosity.
• Calculate 2D correlation function. Also other correlation functions like 3D, sigma-pi would be useful.
• Do the calculation for the different samples.
• Compare results for different samples, compare with theoretical models of galaxy evolution.

A schematic view of the workflow is attached. Click on the image for a full resolution view.

End Results

Examples

Colour images of clusters selected using photometric redshifts. See description in this paper.

-- NicholasWalton - 24 Aug 2005