EUROVO FC

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

EGG

Main

Know

Test

TWiki

AVO Demo 2005: Stellar Science Case

Background

The first part of the case identifies new candidates. The second part demonstrates the use of multi-wavelength data to show characteristic SEDs for typical objects which could be used for comparison with new candidates. 1. Search for new sources in the transition AGB-PN phase by combining existing photometric data in various infrared surveys, principally IRAS and MSX. We identify colours characterising various classes of sources as given by SIMBAD and then find objects with no published identification in the region typical of transition sources. 2. Study of individual sources typical of various stages (see example of Henize 3-401) by reconstructing their Spectral Energy Distribution (SED) by putting together all the information available: FUSE and IUE UV spectra, ground-based optical spectroscopy and photometry, near infrared JHKL'M photometry from 2MASS + ISO IR data (includes PHT-S, LWS + SWS) + IRAS photometry + radio and any other data.

Descriptive Workflow

• Part 1. FLow diagram for selecting and classifying sample by IR colours.
  Load an all-sky image as background allsky.fits.
  • 1.1 The initial sample is taken from the MSX Point Source Catalogue (PSC), V/114. The bands to be used are A (8.28 micron), C (12.13 micron) and D (14.65 micron), with better than 5-sigma detections in A, C and D bands (q_A ge. 2, q_C ge. 2, q_D ge. 2).
    • 1.1.1 This can be achieved using filters in the AVO tool but for speed a pre-loaded, precooked MSX selection is used (~50000 sources). URLforCutAndPaste
    • 1.1.2 Using MSX colours alone does not distinguish object classes very clearly. Excluding sources within 2 degrees of the Galactic plane reduces the YSO contamination and excluding high-latitude sources improves the Galactic:extragalactic source ratio, but at the expense of a lot of genuine candidates. To retain the full MSX-selected sample and improve the discrimination of transition candidates, we need far IR data.
  • 1.2 Load the IRAS PSC (II/125/main) (preload for speed?).
    • 1.2.1 Apply Aladin IRAS filter to select sources with confirmed detections (FQual_60 ge. 2) and create a filtered plane.
    • 1.2.2 Use the cross-match plugin to find the closest MSX source within a radius of 30" for each IRAS source (using IRAS from 1.2.1 as the first catalogue to avoid multiple MSX sources per IRAS source).
  • 1.3 Use AVO tool to add columns to MSX-IRAS catalogue from 1.2.2:
    • 1.3.1 [A-C] = -2.5*log(A/C); [D-60] = -2.5*log(D/60)
  • 1.4 Use the AVO tool plug-in to send (a subsample for speed from) the catalogue from 1.2.2 as a query to SIMBAD with a 30" error circle to allow for IRAS position uncertainty.
    • 1.4.1 Cross-match the catalogue from 1.2.2 with list returned from SIMBAD (as second catalogue), 30" error circle. Matched table should then have all required colums including SIMBAD classification.
    • 1.4.2 Rename 1.4.1 output to MSX-IRAS-SIMBAD
    • 1.4.2 SIMBAD classifications are good enough to show regions of colour-colour space dominated by particular object classes.
  • 1.5 Apply Aladin filters (filters.tar or filters.zip) to the table from 1.4.1, based on source classifications ('Normal' stars, Extragalactic objects, AGB, OH/IR, post-AGB, PNe, YSO and also unclassified sources including IR and radio detections and hitherto unconfirmed PNe candidates). You may use this script creating all filters for all object types. Change the file name or export directory path if necessary.
    • 1.5.1 Save each filtered plane as a VOTable.
    • 1.5.2 Load each table into VOPlot (multiple VOPlot tab).
      • 1.5.2.1 Select (x, y) as [A-C], [D-60] and, with overlay off , plot first object type VOTable.
      • 1.5.2.2 Switch overlay on and select other object types with these axes.
      • 1.5.2.3 colours of known source types (.ps) and unclassified sources.
  • 1.6 Summary of selection criteria for New Transition sources in MSX-IRAS cross-matched sample:
    • 1.6.1 MSX detections >5 sigma crossmatched with IRAS sources with confirmed detections (in the relevant wavebands)
    • Colours in the range A-C >= 0.7 , 0.0 <= D-60 <= 2.5
    • 1.6.3 No existing classification. At present this is based on information in SIMBAD only; eventually more rigorous checks will be carried out.
  • 1.7 2MASS colours could also be used to characterise the New Transition sample further but we do not show this in detail due to time constraints
    • 1.7.1 Use the New Transition sample to query Vizier (a new plugin for the AVO tool)
    • 1.7.2 See additional segregation of AGB-PNeIn2MASS colour-colour plot

• Part 2. Flow diagrams for displaying images and making and measuring spectra and SEDs
  Images and SEDs of sources typical of four transition stages. Scientifically, this shows how most of the newly discovered transition objects are comparatively young, dusty PPNe. We use the VOSpec tool as a plug-in to AVO-Aladin to display the SEDs. High resolution spectra from SSA-compliant archives are obtained by direct discovery via the server selectors in VOSpec or the AVO tool. This includes ISO, HST FOS, SDSS, IUE INES, FUSE SSD and the HyperLeda archive. Catalogued photometric data are extracted as VOTables from Vizier. These and user-supplied data (VOTables or FITS) are accessed using an SSA wrapper which can be created using a web tool via VOSpec, see VOSpec for more details. Magnitudes are converted to physical units using generic expressions for the relevant UCDs e.g. PHOT_JHN_J. If greater accuracy is needed the user can prepare a VOTable themselves e.g. using TopCat.
  Data in green are selected via the SSA server in VOSpec using 0.1 deg search radius ; other data are loaded via the prepared wrappers.
  • 2.1 Heavily obscured AGB star: OH 26.5+0.6 18 38 32.51 -05 23.59.2
    • 2.1.1 Imaging display using AVO-Aladin
      • Non-detection at wavelengths shorter than H-band; show very red object in 2MASS JHK RGB could omit for speed, just point out that in VOSpec the 2MASS J point is an upper limit.
    • 2.1.2 Spectral Profile display using VOSpec
      • 2.1.2.1 High resolution spectra
        • ISO
          • SWS01 #3rd in the list (1st SWS01)
          • LWS02 #6th in the list (1st LWS02)
        • User-supplied OH radio spectrum (Etoka & Diamond in prep.; RadioNet are planning to enable single-dish archive access) switch to lines in display
      • 2.1.2.2 Photometric points OH26.5+0.6SSAWrapper.xml
        • ISO PHOT switch to lines in display
        • 2MASS, MSX, IRAS, Radio (1991A&A...248..555W via II/199A) switch to dots in display
    • 2.1.3 Comments: OH265.+0.6 is a very red AGB source not detected at wavelengths shorter than the 2MASS-H band; strong silicate absorption at 10 and 18 microns indicative of O-rich optically thick shell; double peak OH maser emission indicating a expanding shell; must be about to end the AGB phase. Possible variability is detected if we compare MSX at 11 microns with IRAS 12 micron fluxes.
      • You can zoom in the OH maser emission and the silicate absorption feature in VOSpec.

  • 2.2 Bright post-AGB star with no hot dust: HD 161796 17 44 55.47 +50 02 39.5
    • 2.2.1 Imaging display using AVO-Aladin
      • Bright optical star; show non-red object in 2MASS JHK RGB could omit for speed, see VOSpec SED
    • 2.2.2 Spectral Profile display using VOSpec
      • 2.2.2.1 High resolution spectra
        • ISO
          • LWS01 #1st in the list (1st LWS01)
          • SWS01 #2nd in the list (1st SWS01)
        • IUE
          • IUE LWP05412 #1st IUE spectrum in the list switch to lines in display
          • IUE SWP29556 #last IUE spectrum in the list switch to lines in display
      • 2.2.2.2 Photometric points HD161796_SSAWrapper.xml
        • ISO PHOT switch to lines in display
        • BVRI (II/237/colors , Ducati et al.), 2MASS, IRAS, Radio (1991A&A...248..555W via II/199A) switch to dots in display
    • 2.2.3 Comments: Use the Black Body fitting to identify two components, giving something like 5000 K for the central star and 128 K for the dust in the shell. This shows that HD 161796 is a typical post-AGB star in which both the central star and the cool envelope are clearly emitting as two independent BBs. This is the result of the evolution of a low mass star in which the central star is still not hot enough to ionize the envelope, which has become very cool. The central star is actually a low-gravity F5-type star. We stress that bright evolved stars can only be identified as post-AGB stars due to the presence of this cool component which was first recognized after the IRAS all-sky survey some 20 years ago.

  • 2.3 Very young PNe with a lot of warm dust in the CSE: IC 418
    • 2.3.1 Imaging display using AVO-Aladin
      • 2.3.1.1 Use AVO tool to search HST mission log around IC418, radius 1 arcmin.
        • Load PC (planetary camera from WFPC2) images U66B1006M, U35T0905, U66B1002M.
        • In order to align the images, tag the central star in U66B1006M. U66B1002M is already closely aligned with this image.
        • For U35T0905, get the Properties of the plane and Edit the Astrometric Reduction in order to line the tag up with the central star. This is done by setting CRPIX1 = 427, CRPIX2 = 444.
      • 2.3.1.2 Make a (spectacular) RGB image with
        • red: U66B1006M = F658N (NII)
        • green: U35T0905 = F656N (Halpha)
        • blue: U66B1002M = F502N (OIII)
    • 2.3.2 Spectral Profile display using VOSpec
      • 2.3.2.1 High resolution spectra
        • ISO
          • LWS01 #1st spectrum in the list (1st LWS01)
          • SWS01 #2nd spectrum in the list (1st SWS01)
        • IUE
          • LWP24371 #last IUE LWP in the list switch to lines in display
          • SWP46378 #last IUE SWP in the list switch to lines in display
        • FUSE switch to lines in display
      • 2.3.2.2 Photometric points IC418SSAWrapper.xml
        • 2MASS, IRAS, Radio (1991A&A...248..555W via II/199A; NVSS, PMN, PKS via VIII/74) switch to dots in display
    • Comments: IC 418 is already a very young PN extended over several arcsec in the optical, seen in the RGB images created from HST data.
      • Zoom in on the FUSE+IUE data in VOSpec to show a very nice combination of spectroscopic features of very high quality:
        • P-Cygni profiles due to the stellar wind from the hot central of the PN at various lines (e.g. C IV line at 1550 A).
        • Nebular emission lines from the ionized gas like CIII 1909 A or OII 2470 A
        • A broad absorption bump at 2200 A due to dust in the shell
        • Much hotter continuum from the central star with respect to HD 161796, seen by comparing the IUE data in VOSpec.
      • There is a characteristic excess in the 2MASS J-band photometry which is due to the presence of a strong HeI triplet at 1.083 microns which falls in the J-band filter profile.
      • The PAH feature at 11.3 microns is clearly visible indicating that the dust in the nebula is C-rich.
      • The cool dust observed by IRAS and ISO is the remnant emission from the AGB shell.

• Part 3. Post-demo follow-up of candidate sources could include:
  • 3.1.Images:
    • 3.1.1 NVSS/FIRST (via AVO-Aladin, NB NVSS is better via VLA but FIRST via SkyView)
    • 3.1.2 Spitzer Galactic FLS description; images (but inside zip files).
    • 3.1.3 Examples show the sources highlighted (see the measurement frame, blue symbols) faint IRAS 25 micron counterpart? top left inside box - line of sight contamination? Faint NVSS counterpart (see zoom window)
  • 3.2 Catalogues revealing other diagnostics of AGB-PNe or not (some also shown in above image links): OtherCatalogues
  • 3.3 Use of MSX colours for distinguishing between C- and O-rich Miras
  • 3.4 Extending the search to extragalactic transition sources using Spitzer data taken on nearby galaxies of the local group. The SINGS Legacy Program has one such galaxy, NGC 6822 (see here). There are IRS, IRAC, and MIPS data available from the Spitzer archive (search by position using RA = 19h44m56.63s and DEC= -14d47m21.4s, J2000), although at present only the IRS data are downloadable. This may become feasible as SINGS data are becoming available.

Data (needs updating)

• Part 1.
  • Relevant catalogues accessible from VizieR.
    • IRAS data Via Vizier, see 1.2
    • MSX data Via Vizier, see 1.1.1
    • 2MASS Via Vizier (optional)
  • SIMBAD
  • Precooked selections
    1. MSX, ACD quality ge. 2
    2. IRAS, 60um quality ge. 2
    3. IRAS+MSX quality selected, cross-matched, A-C and D-60 colours added
    4. SIMBAD counterparts
    5. MSX+IRAS cross-matched with SIMBAD
  • OLD** Do Not Use** Cross-matched selections filtered by object type (8 files)
    • ObjectClassesVots.tar or ObjectClassesVots.zip
• Part 2. From the AVO prototype:
  • Target name: IRAS 10178-5958
  • Search radius: 1 arcmin
  • Search Catalogues in Vizier: output list is 22 catalogues!
  • Select only the following ones for display:
    • II/246 (2MASS)
    • VI/110 (IUE: LWP13296, LWP28009, SWP33602, SWP50649)
    • V/114 (MSX)
    • VI/111 (ISO: SWS01, TDT 08400730; PHT40, TDT 08400731)
    • II/125 (IRAS)

A few figures for catalogue loading:

For each catalogue I give the full size, the number of records and RAM size required to load the full catalogue, a script that makes the selection directly to vizier, and the size of the selected sample and needed RAM.

Loading both filtered catalogues can be done with 100Mb memory only and in less than one minute. Conditions for filtering are q_A,q_C,q_D ge 2 for MSX and QF60 ge2 and latitude in the range -6..+6 for IRAS.

Applications

Acknowledgement

• MSX_IRAS_SIMBAD.xml: MSX_IRAS_SIMBAD with colors