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 HISAComplex:

Distance ~ 2000 pcAngular Size ~ 3 deg2

Physical Size ~ 100 pc2

H I Self-Absorption (HISA) Cold H I visible asintricate shadows against warmer H I emission in the Galactic disk.

HISA comes in bothlarge, organizedcomplexes and small, random ``fluff’’.

Northern Coalsack Cyg OB7 HISA

Distance ~ 800 pcAngular size ~ (3 deg)2

Physical size ~ (40 pc)2

A Big HISA Cloud

IC 2944(Thackeray's Globules)

Distance ~ 1800 pcAngular size ~ < 40”Physical size ~ < 0.3 pc

Local HISA Filament

Distance ~ 100 - 500 pcAngular 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

SouthernSurvey(SGPS;ATCA)

VLASurvey(VGPS)

CanadianSurvey(CGPS;DRAO)

McClure-Griffithset 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 Brian’s 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

See Example.

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

See Example.

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 Foundationthrough Arecibo Observatory.