Presentation on theme: "Building a Simple Image Server from Available Tools Steven Gibson (Arecibo Observatory, Puerto Rico) NVO Summer School, Aspen, 2006 Petr Škoda (Ondřejov."— Presentation transcript:
Building a Simple Image Server from Available Tools Steven Gibson (Arecibo Observatory, Puerto Rico) NVO Summer School, Aspen, 2006 Petr Škoda (Ondřejov Observatory, Czech Republic )
Motivation Want to learn the basics of SIAP, which was not covered in detail in the lectures. Have been tasked by employers with making ongoing surveys part of the NVO. Have existing data that want to share! Start with a small, simple set of data...
Perseus HISA Complex: Distance ~ 2000 pc Angular Size ~ 3 deg 2 Physical Size ~ 100 pc 2 H I Self-Absorption (HISA) Cold H I visible as intricate shadows against warmer H I emission in the Galactic disk. HISA comes in both large, organized complexes and small, random ``fluff.
Northern Coalsack Cyg OB7 HISA Distance ~ 800 pc Angular size ~ (3 deg) 2 Physical size ~ (40 pc) 2 A Big HISA Cloud
IC 2944 (Thackeray's Globules) Distance ~ 1800 pc Angular size ~ < 40 Physical size ~ < 0.3 pc Local HISA Filament Distance ~ 100 - 500 pc Angular size ~ 1' x 5' Physical size ~ 0.03-0.1 x 0.13-0.25 pc A Small HISA Cloud
Why Study Cold H I ? Abundant ISM phase (30% by mass) Quiescent gas (needed for star formation) Relation to molecular hydrogen (condensation?) Intricate small-scale structure (turbulence?) Probe of Galactic structure (spiral arms)
HISA Census Motivation How is HISA distributed in the Galaxy? What does this distribution tell us about the mechanism(s) producing the HISA? What does it tell us about Galactic structure? How does the HISA relate to the rest of the ISM? Large area - unbiased survey of cold H I clouds (not merely known dark/molecular clouds) High angular resolution - many HISA features are missed at low resolution
(map: Taylor & Cordes 1993 electron density) International Galactic Plane Survey Souther n Survey (SGPS; ATCA) VLA Survey (VGPS) Canadia n Survey (CGPS; DRAO) McClure-Griffiths et al. (2005) Stil et al. (2006) Taylor et al. (2003)
SIAP-like Server Examples 36 CGPS HISA 2-D tile images Modified Cone-search from Brians exercise Comma-separated variable (CSV) table of image metadata read into MySQL database This read in turn by java routines Search for atlas tiles covering desired position, output links to FITS tiles and canned GIF images Create cutout images covering desired area using C code called by CSH scripts called by java/HTML Access both searches with same HTML web form
SIAP Server, Part II Saada package available from France Installation difficult, but lots of features available Read PostgreSQL data into package Requires j2ee Can display images overlapping cone search Can read into Aladdin and do object queries As with previous example, some confusion between RA+DEC and GLON+GLAT coordinate systems, due to current limitations of software
Conclusions SIAP server works on both systems Saada is useful for keeping local data and browsing Relations flexible but problem to adopt for custom work (like cutout service) Version 1.3 has SIAP, Conesearch Next one will have SSAP, ? End of Sep 2006 Steve's solution compact, robust – example of custom processing in VO environment Thanks for Summer School templates (Cone.jsp)
This work was supported by grant GAČR 205/06/0584 and by the U.S. National Science Foundation through Arecibo Observatory.