July 13, 2004P. Padovani, The A-Star Puzzle1 A-Stars and the Virtual Observatory Paolo Padovani, ST-ECF/ESO AVO Science Manager The Virtual Observatory

July 13, 2004 P. Padovani, The A-Star Puzzle 1

A-Stars and the Virtual Observatory

Paolo Padovani, ST-ECF/ESO

AVO Science Manager

• The Virtual Observatory (VO)• Europe and the VO: the Astrophysical Virtual Observatory • A-Stars and the (A)VO: concrete applications Disclaimer n. 1: Big topic, good for a whole workshop Disclaimer n. 2: Extragalactic astronomer!

The Virtual Observatory and A-Stars


Astronomy in the XXI centuryRadical changes are needed!

Huge surveys: 100M sources at <3k spectra/night >100

yr! Ever fainter sources: surpassed the identification limits of 8 -

10m telescopes (Rmag ≈ 25) Huge data collections: downloading Sloan Digital Sky Survey

(SDSS) DR2 (~ 1/3 of total) images (5 Tb) ~ 1 yr at 200 kb/s (ESO’s speed); catalogs (1.4 Tb) ~ 3 months. On DVDs ~ 1,000 of them. And analysis?? (similar size for MACHO, 2MASS etc …)

Ever increasing amount of data


R ~ 25.5, VLT/FORS2, texp ~ 2.5 hrs (Szokoly et al. 2004)


Astronomical Data Explosion

P. Quinn

~ 100 Gb/night


ESO/ST-ECF Science Archive Facility holdings


The solution?

Data mining to increase observing efficiency intelligent pre-selection

Statistical identification to diminish need for a spectrum multi-wavelength, multi-parameter analysis

In-situ analysis to avoid download Easy and smart access to all archives and

data providers


The name: Virtual Observatory

An innovative, evolving system, which takes advantage of astronomical data explosion

It will allow users to interrogate multiple data centres in a seamless and transparent way and to utilize at best astronomical data

Data analysis tools and models will be made more accessible It will allow new science by moving Astronomy beyond era of

“classical” identification by combining all available information Good communication common language! Adoption and

definition of VO standards and protocols within the International Virtual Observatory Alliance (IVOA: http://ivoa.net)

And it’s all happening now …


International Virtual Observatory Alliance

Mission To facilitate the international coordination and collaboration necessary for the development and deployment of the tools, systems and organizational structures necessary to enable the international utilization of astronomical archives as an integrated and interoperating virtual observatory SVO


So what …? The VO will make life much easier for all astronomers,

even those not involved with colossal surveys, huge teams, and Tb of data! Web: all documents of the world inside your computer VO: all astronomical databases in the world inside your

computer Concrete example:

Find all the high-resolution spectra of A-type stars available in all astronomical archives in a given wavelength range

Tell me which ones are in raw or processed form Allow me to retrieve them If raw, give me access to the tools to reduce them on-the-fly Very time consuming, if at all possible, at present


Virtual Observatory in Europe AVO Project started November 2001

Three-year, 5 M€, Phase A project, funded by the European Commission (FP5) and six organizations: ESO, ESA, AstroGrid, CNRS (CDS, TERAPIX), University Louis Pasteur, JBO

Manpower: ~ 17 FTEs/yr total, 50/50 EC and partners Next step: EURO-VO, implementation phase (some

EC funding secured, need more) Visit us at http://www.euro-vo.org Science Working Group established two years ago to

provide scientific advice to AVO Project; implementation of selected science cases through demonstrations


The AVO Prototype

Evolution of Aladin (Centre de Donnés astronomiques de Strasbourg [CDS])

Downloadable Java application (http://www.euro-vo.org/twiki/bin/view/Avo/SwgDownload)

Extensible toolset with plug-ins which allows easy access to images, spectra, catalogues, with overlays, plotting facilities, and a cross-correlation utility

Still prototype but also research tool: first refereed, VO-based scientific paper “Discovery of optically faint obscured quasars with Virtual Observatory tools”, P. Padovani et al., A&A, in press (astro-ph/0406056)ST-ECF/ESO Press release May 28


A-star VO Cases

1. Establishing open cluster membership2. Are chemically peculiar A-type stars more

likely to be X-ray emitters than normal A-type stars? (Damiani et al., 2003)


Open Cluster MembershipOpen Cluster Membership

Pleiades:POSS IIimage


Loading cataloguesLoading catalogues

parallax


Plotting Data: Parallax HistogramPlotting Data: Parallax Histogram

cluster parallax = 8.46±0.22 mas


Colour-magnitude diagramColour-magnitude diagram

can correct for reddening by adding a new column

ZAMS


Colour-magnitude diagramColour-magnitude diagram

parallax


Open Cluster Membership

Can be done now with existingtool, will be easier to do in thenear future


Available archive dataAvailable archive data

2 clicks away from journal articles!


MAST data in detail Cross-correlation of Sky2000 star catalogue with Multi-

mission Archive at STScI (MAST; Optical/UV) Out of 22,400 A-type stars:

• 754 have International Ultraviolet Explorer (IUE) data, for a total of ~ 10,000 observations

• 128 have non-IUE (FOS, GHRS, STIS, FUSE, EUVE, Copernicus, HUT, WUPPE, BEFS) data, for a total of 1,700 observations, ~ 60% of which are spectra

• How much else is available?


Peculiar A Stars in the X-raysPeculiar A Stars in the X-rays

Renson et al. (1991) catalog of 6684 chemically peculiar stars,4736 of which A-type (equatorial projection)


HD catalog (blue; 272,150 sources) with A-type stars (yellow; 72,154) selected (equatorial projection)

Peculiar A Stars in the X-rays: Comparison SamplePeculiar A Stars in the X-rays: Comparison Sample


WGACAT of ROSAT PSPC observations, 88486 sources (equatorial projection)

Peculiar A Stars in the X-raysPeculiar A Stars in the X-rays


Chemically peculiar A-type stars in the

X-rays Cross-correlation of Renson et al. CP catalogue (A-type only) with WGACAT: 79/4736 matches = 1.7±0.6% (3; spurious matches subtracted). Magnetic only: 22/1433 = 1.5±0.7%

Cross-correlation of HD A-type stars with WGACAT: 392/72154 = 0.54±0.03%; correcting for CP star contamination (=10%; e.g., Monin et al. 2002) ~ 0.4%

Cross-correlation of SAO A-type stars with WGACAT: 351/47230 = 0.7±0.1%; correcting for CP stars one gets ~ 0.6%

Chemically peculiar A-type stars are ~ 3 - 4 times more likely to be X-ray sources than normal A-type stars. Magnetic field appears not to play a role.


Chemically peculiar A-type stars in the radio

band? Cross-correlation of Renson et al. CP catalogue

(A-type only) with (almost) all-sky radio catalogues down to ~ 1 mJy gives null results

Expected, given fluxes of few detected sources so far ( 1 - 2 mJy, e.g., Drake et al. 1987)


Summary The Virtual Observatory is happening, because it

has to! Handling and manipulating astronomical data

and tools residing at various locations around the world will be made much easier than it is now

Everybody will benefit, including A-type star researchers!

Tools are available now to help you with your work

July 13, 2004 P. Padovani, The A-Star Puzzle 27 AVO prototype downloadable at

http://www.euro-vo.org/twiki/bin/view/Avo/SwgDownload

AVO Web PageAVO Web Page


Astronomical Data on the WebAstronomical Data on the Web

Documents

July 13, 2004P. Padovani, The A-Star Puzzle1 A-Stars and the Virtual Observatory Paolo Padovani, ST-ECF/ESO AVO Science Manager The Virtual Observatory