Gould Belt

Aim

Identification of the component parts of the Gould Belt using existing multiwavelength catalogues. This will form the basis of pointing position data for a future JCMT HARP (science case) survey of Star Formation in the local Solar Neighbourhood.

The data will be used to produce colour-colour and colour-magnitude plots to identify the pre-stellar and stellar components in the Gould Belt. We will analyse the output to look at the spectral ages of stars and test the hypothesis that Gould Belt SF was induced by the passage of a Supernova Shock Wave.

Data

Catalogues containing Galactic sources at U-band and longer wavelengths. Most of these will only cover part of the Gould Belt and most objects of interest will only be detected at some wavelengths as a wide variety of objects are relevant to this case, from massive hot OB stars to cool YSO (young stellar objects). Privide links to explain photometry for catalogues in magnitudes. Most catalogues contain astrometric and photometric errors or quality factors, check if there are additional systematic errors. (Typical total astrometric uncertainty for fainter/difficult sources, to be used as a limit in initial crossmatching, arcsec)

  • INT-WFS merged object catalogue sky coverage (now mostly complete) available via AstroGrid at cam (2 arcsec)
  • 2MASS available via AstroGrid at roe (5 arcsec)
    • J H Ks (1.24 1.66 2.16 Ám) mags
  • DENIS Vizier B/denis/denis (1 arcsec)
    • Gunn-i J Ks (0.82 1.25 2.15 Ám) mag
  • IRAS Vizier II/125/main (30 arcsec)
    • 12, 25, 60, 100 um, Jy
  • ISOGAL Vizier II/243/psc1 (possibly also psc2) (15 arcsec)
    • 7 15 um (mags)
  • MSX Vizier V/114/msx_gp (possibly also msx_main) (5 arcsec)
    • A C D E (8.28 12.13 14.65 21.34 um) Jy
  • NVSS Vizier VIII/65 (25 arcsec)
    • 1.4 GHz mJy
  • Spitzer - check exact overlap with Gould Belt
  • Also catalogues of methanol and other lines diagnostic of SF
  • SIMBAD (for source classification; also contains some B and V mags)
  • Upcoming SCUBA2 continuum and line sub-mm legacy surveys

Strategy Outline

  1. Establish region limits
    The Gould Belt covers a large area; the survey area suggested for the JCMT suggests 1000 sq. deg. concentrated in 100 isolated cores and 10 major regions. These include the Pipe nebula, IC 5146, the Cepheus and Polaris flares and the major Lupus, Taurus, Serpens and Perseus clouds and also Orion (**check which part)
  2. Construct learning set
    Use SIMBAD classifications and other a-priori knowledge **refs? to obtain a sample of objects of known types and establish their typical colours (NB this will not necessarily be 100% accurate but should be statistically adequate).
    • Object types of interest (**expand and add more diagnostics) - these are indicators of recent star-formation, e.g.
      • Early-type such as B stars and clusters (B-V - photospheric, scattered)
      • Young lower-mass stars - nebulosity, warm shells, photspheric lines ([7-15], B-V)
      • Very young stars - cool and/or thick shells ([60-25], [170-100])
      • HII regions, YSO jets (Halpha, radio)
  3. Establish distance criteria
    (how? Limiting mags? Parallax? Radial velocities?)
  4. Attempt to classify all stellar objects in regions of interest, establish their ages and compare with SN shock wave passage model. (**develop)

Workflow for learning set

  1. Serpens cloud region
    • Contains high- and low-mass star-forming regions
    • Provisional main centre J2000 18 29 49 +01 14.8 (Gal 31.57, +5.38), 10 degree radius.
      • Some catalogues may return >>10^4 or even 10^5 sources if there is no filtering
    • J2000 18 41 00 -3 00 00 2 degree radius circle is a more manageable region for initial tests (B1950 18 38 22.740 -03 02 52.73 )
      • Query Vizier catalogues as above (AstroGrid)
        • Select sources with better than 3-5 sigma detections or equivalent
        • DENIS gives ~10^6 sources even in this region, so
      • Query SIMBAD (2019 objects) and load into MySpace
      • 2MASS also available directly from AstroGrid
      • Query INT-WSF merged object catalogue when available (AstroGrid)
      • Query Spitzer catalogues when available
    • Cross-match tables against SIMBAD
      • Adjust search radii and matching strategy to minimise spurious/duplicated matches and missing matches
      • Check for any systematic astrometric offsets which can be corrected
    • Establish photometric transformations and any corrections needed
      • **How accurate do we need to be?
    • Make colours (add columns)
    • Perform colour-based queries on MySpace tables
    • Use additional selection criteria based on distance indicators - magnitudes, **?
    • Visualise

Required new capabilities

  1. Essential
    • ADQL interfaces to CDS and/or HEASARC data
      • Cone search of HEASARC catalogues available and could be used but involves unneccesarily bulky data sets and more scripting
    • Coordinate conversions (e.g. IRAS is in B1950)
      • Built in as a parameter catalogue selection or data extraction (cf Vizier)?
      • Separate tool e.g. using STILTS?
      • Built-in to Cross Matcher and other tools?
    • Access to SIMBAD as a catalogue via AstroGrid
    • Allow for using very large catalogues e.g. DENIS contains 150 000 000 sources
    • Access to Spitzer catalogues
  2. Desirable
    • Use of ColourCutter for some pre-selection
    • Automatic selection (within workflows) from MySpace tables e.g. colour cuts
      • Can presently be done manually using TopCat etc.

-- AnitaRichards - 25 Feb 2005

Progress

AnitaRichards - 10 Feb 2006 (after meeting with JeremyYates)

  • Trial data sets
    • UCL Summer Student selected data from 2MASS and IRAS for several regions, cross-matched using 45' search radius.
    • Used TopCat to make colours (J-H) (H-K) (12-25) (25-60) (60-100)
    • Used local UCL code to produce model values of colours for black bodies of various temperatures, plotted against data and fitted by eye.
    • See GouldBeltFeedBack for more information from trial.
  • Future progress
    • Modify ColourCutter to work on IRAS and 2MASS or other IR datasets AMSR
    • Tool to produce Black Bodies as tables of F v. Lambda and generate model colours JAY ?
      • VOSpec goes one further and plots curves - can the part generating the model be extracted? or wrap Jeremy's code?
      • This would need a separate tool to generate colours
    • Need Mid-IR (Spitzer) data
      • Clarify C2D source table availability with Evans JAY
      • If this is in IPAC format, needs converting to VOTable. This can be done using TopCat or STILTS prototype (short command) which could be inserted in script or workflow. AMSR
    • Flux (and magnitude) unit conversion, possible aperture matching
    • Other data as above
    • More advanced model SEDs
      • Mocassin generates SEDs (100s-1000s points) from UV to mm for Galactic nebulae.
        • FORTRAN 90, takes one input parameter file and a number of config files which could be static - cf SExtractor. Multiple outputs but not all relevant. Not compute- nor volume-intensive.
        • Modify to take small number of user input parameters and produce one main SED output JAY
    • Fitting
      • huntfit3 (A. Efstathiou) takes a family of models and uses a chisq procedure to find which one is the best match for an SED constructed from observational data. IDL, works on 10s - 1000s of spectral points. Customised for certain input formats.
        • Modify for wrapping JAY
        • Use IDL or rewrite?
        • Extensible to what kinds of spectra? (e.g. what resolution, wavelength range etc.)
          • already does optional partial K-correction - may only be usable at low z.

Topic revision: r9 - 2006-03-03 - 19:04:21 - AnitaRichards
 
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