Astronomer, automated search engine
Determine the galaxy environment of fields used in the search for
Type Ia Supernova at cosmological distances.
Optical survey data, infrared survey data, dust maps, e.g.
Schlegel et al
Supernovae searches (e.g. Perlmutter et al, 1999) typically programme observations of a set area of sky (the area imaged being dependent on the size of the SN sample desired, for SN samples at lower redshift larger areas of sky are required due to volume effects). The selection of the correct sample of Type Ia's at the imaging search stage is important because confirmation of the SN comes from spectroscopy often obtained on the largest ground based telescopes, such as the VLT, for the higher (z>0.7) redshift SN. Therefore it is important to minimise 'wasted' spectrscopic and followup time on Type II SN.
A problem with current techniques, is that for any candidates discovered there is an uncertainty as to whether or not the candidate is in fact the desired Type Ia SN. Whilst Type Ia SN are typically brighter than Type II core collapse SN, some Type II's can contaminate the sample.
A rapid knowledge of the environment in which any SN is discovered can improve the situation. Pre-determination of the galaxy redshifts utilizing photometric means enables an estimate to be made of the candidates distance upon discovery, and thus a better estimation of which type of SN it is. Further, information on the galaxy, for instance it's morphological type, may also aid in rapid classification of the SN. Type Ia's being formed by an explosion resulting from the accretion of matter onto a degenerate star are found in all classes of galaxy. However, Type II's, which result from the catastrophic explosion of a massive star have not been found in early elliptical galaxies.
Poznanski et al (2002) discuss the use of SDSS multiband photometry to determine the type of SN out to redshifts of 0.75.
For SN search areas:
- search literature and published sources for possible spectroscopic redshifts of galaxies in fields.
- search archives for spectroscopic data of objects in field > determine redshifts of galaxies in fields using perhaps automated techniques such as devloped for the 2dFGRS (see Colless et al, 2001)
- Locate multicolour broadband optical data for the search fields
- Determine photometric redshifts to galaxies in the fields using a variety of techniques (e.g. hyperz, more recently (2002) Z-Peg).
- identify possible galaxy clusters (see e.g. OpticalNearIRGalaxyClusterSelection)
- cross reference position of newly discovered SN from search. If located in a galaxy for which the redshift is known from one of the above techniques, return an assigned redshift for that SN (together with estimation of error).
- return morphological information of the galaxy in which the SN candidate is located (if applicable)
Colless et al
, 2001, MNRAS, 328, 1039
Goldhaber et al
, 2001, ApJ
, 558, 359
Perlmutter et al
, 1999, ApJ
, 517, 565
Poznanski, D. et al
, 2002, PASP, 114, 833
: Please add comments below. This area should be used for refinement of the above document. If you want to ask questions or start a dialogue with the author, please use (or create) a topic in the Science Problems Forum
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, refer to the ScienceProblemList
: Once the refinements here and comments in the forum die down, perhaps you could rewrite the problem, incorporating the comments and refinements.
An AG Phase-B driver
- 17 Apr 2002
Two (connected) issues arising:
Pre-detection images of the SN region are needed for the possibility of detecting the precursor as well as the environment. This will involve searches in the footprint of archive observations and possibly the need to refine their astrometry, photometry etc.
Smartt, Stephen J., Gilmore, Gerard F., Tout, Christopher A., & Hodgkin,
Simon T. 2002, Astrophysical Journal The Nature of the Progenitor of the
Type II-P Supernova 1999em
SNe/SNR may be in heavily obscured environments (e.g. Arp 220, M82).
Although the appearance of the radio SN (let alone the SNR) lags the optical, this may be the only way to get an accurate position. Once an SNR can be resolved, radio VLBI can measure expansion accurately enough to give a secure distance in months or years. The SNR morphology tells you about the environment. If the SN is in a starburst, pre-outburst archive radio images will also tell you about the environment. If it is no too obscured Halpha provides similar information.
Smith, Harding E., Lonsdale, Carol J., Lonsdale, Colin J., & Diamond, Philip
J. 1998, Astrophysical Journal A Starburst Revealed---Luminous Radio
Supernovae in the Nuclei of ARP 220
McDonald, A. R., Muxlow, T. W. B., Pedlar, A., Garrett, M. A., Wills, K.
A., Garrington, S. T., Diamond, P. J., & Wilkinson, P. N. 2001, Monthly
Notices of the Royal Astronomical Society Global very long-baseline
interferometry observations of compact radio sources in M82
- 16 May 2002
Just to clarify - the issue of the rapidly locating possible progenitors to nearby, newly notified, SN (as in the Smartt et al work) is not quite what I'm getting at here. In the case of the Smartt et al work, the SN is discovered and the trick is looking back through the archives to see if there was anything known at that position before the SN went off.
Searches for Type Ia's at high redshift are based on searching fields for which reference data is available, then performing image subtractions to identify the SN candidates. The poitn behind this case, is knowing which fields are going to be surveyed for SN, then enabling the determination of the redshifts to the galaxies in the field. Then if a SN is found in one of those galaxies, the redshift would be known (perhaps only in a statistical sense if its a photometric determination).
As to SN in obscured regions, again this is more of an issue for nearby SN. Mattila and co workers have been using near infrared imaging to search for these obscured SN - especially important in starburst galaxies (see e.g. Mattila et al, 2002, astro-ph/0202087
- 30 May 2002
See also CommonGroup
of use cases
needed include: Astrometric Alignment;
Least squares fit; Express result as probability; Proper motion; Measure noise in data
and related cases in order to rule out nearby stars and even near-Earth objects there need to be criteria such as BrownDwarfRecognition
- new use case to include those below - so that user can see if adequate data already exist.
- 31 Jul 2002
- 24 Jan 2002