Exploiting Virtual Observatory and Information Technology: Techniques for Astronomy
Nicholas Walton
AstroGrid Project Scientist

Institute of Astronomy,
The University of Cambridge

Lecture #5 Goal:

VO Applications

Science Usage

Summary: Lecture #5

Review of VO Client Side Tools

Examples of Usage

Creating the H-R diagram

Discovery of Brown Dwarfs

Stars in Open Clusters

Discovery of Type 2 QSO's

P-AGB (OH masers, PN) stars

VO Client Side Applications

Applications are now available which conform to VO standards

Powerful tools exploiting the uniform data access methods

Lecture #6 will cover server side applications

Aladin

A sophisticated data visualiser and workbench

Developed at CDS - Strasbourg

Two versions available:

Mainstream Aladin v2.503: http://aladin.u-strasbg.fr/AladinJava?frame=downloading

VO enabled: AVO-Aladin v2.000: http://www.euro-vo.org/twiki/bin/view/Avo/SwgDownload

Many new features in latest AVO-Aladin v2.0 version

Aladin: Multi-view

HST ACS

Ultra Deep Field

variable size cutouts generated from loaded images

Aladin: Image Cutout Services

e.g. SWIRE cutout service

Cutouts generated remotely

Aladin: image browsing for distributed data

IDHA data model for describing FOV: Data Tree

Re-sampling to pixel grids

Matched zoom and pan

Simple image registration

Pixel re-sampling

Aladin: Query by List

Remote Cross-Matching: 'bringing the computation to the data'

Multiple Cone Searching:

'stream-lining batch requests'

Supports X-Match for sparse or complex distributions of sources

VizieR & SIMBAD

>105 sources

e.g. entire IRAS

VOSpec

VO spectral access tool

Developed at ESAC

Startup from:

http://esavo.esa.int/vospec/

Specview

A java application for analysis and visualisation of 1-D spectra

Developed at STScI

Download from

http://www.stsci.edu/resources/software_hardware/specview

Also available as a helper app to e.g. Aladin

VOPlot/ VOPlot3D

Java tools for the visualisation of tabular data in 2-D and 3-D

Developed for VO-India by Persistent Systems and IUCAA

Available in standalone or plugin formats

http://vo.iucaa.ernet.in/~voi/voplot.htm

Mirage

'Mirage is a Java-based software tool for exploratory analysis and visualization of images and multi-dimensional numerical data from an arbitrary domain of study.'

Developed by Tin Kam Ho at Lucent Technologies

Available at:

http://cm.bell-labs.com/who/tkh/mirage/index.html

http://skyservice.pha.jhu.edu/develop/vo/mirage/default.aspx

TopCat

TOPCAT is an interactive graphical viewer and editor for tabular data

A Starlink developed Java app

Available from:

http://www.star.bris.ac.uk/~mbt/topcat/

AstroGrid: Applications via Java WS

AstroGrid is making available many of the preceeding applications via Java Web Start

http://java.sun.com/products/javawebstart/download.jsp

Applications are listed at http://software.astrogrid.org/jnlp/

VOStat: Statistics via the VO

Provides a quite of statistical tools

http://vostat.org

Includes (partial) access to the 'R' statistics package: http://www.r-project.org/

Example usage given at:

http://vostat.org/demos/index.html

Science Examples

Putting the applications to use ...

The H-R Diagram

Using VO Tools to construct a H-R diagram

The flow of this case is as follows

Search registry for a stellar catalogue with absolute magnitudes or objects at a set distance (e.g. Members of a cluster)

Get relevant catalogue – in this case the Gliese catalogue

Vizier: http://vizier.u-strasbg.fr/viz-bin/VizieR

HEASARC: http://heasarc.gsfc.nasa.gov/cgi-bin/tam/conetest.pl?table=cns3&RA=0.0&DEC=0.0&SR=180.0&VERB=2

Use VOPlot of TopCat to display catalogue

Create an absolute magnitude table column

Vabs = Vmag + 5 + 5 log p (p is parallax in arcsec)

Vabs vs B-V to show the H-R diagramme

Select the objects bottom left

As expected – identified as White Dwarfs

Case developed for the US-VO 2004 Summer School

http://www.us-vo.org/summer-school/proceedings/exercises/HRDiagram.htm

Brown Dwarfs

Searching for Brown dwarfs based on a z-J > 3 mag

Make use of 2MASS and SDSS IR and Optical photometry

Search using Open Sky Query

http://openskyquery.net/Sky/skysite/browse/Browse.aspx

SELECT o.objId, o.ra,o.dec, o.type,

t.objId, t.j_m, o.z

FROM SDSS:PhotoPrimary o,

TWOMASS:PhotoPrimary t

WHERE XMATCH(o,t)<2.5

AND Region('Circle J2000 16.031 -0.891 .10')

AND( o.z- t.j_m)>1

Results can be saved as VOTable for further analysis

Example developed for the NVO 2004 Summer School

http://www.us-vo.org/summer-school/proceedings/exercises/BrownDwarf.htm

Science from the US-VO

Stars in Open Clusters

Locate stellar data for the Pleiades cluster

Use the Hipparcos and Tycho catalogue

Find the parallaxes for stars in the cluster: ~ 9 mas in this case

Deredden the B-V colour

(B-V)o = (B-V) – E(B-V) = (B-V) – 0.04

Plot Vmag vs (B-V)o to see the HR diagramme for the stars

Those of the ZAMS have parallaxes ~9 mas : cluster members

Those outliers : field stars

Use of Aladin to quickly select objects and view on the image plane

This scenario showing use of Aladin given by Padovani at the ESO NEON Archive School (2004)

http://www.eso.org/~ppadovan/neon.demo

AstroGrid/AVO Demo 2004
discovering distant quasars from multi-λ data

1st Science from the AVO

Data

GOODS: Bviz Images & Catalogues

CDF-S (+UDF), HDF-N : 61647 sources

Deep X-ray Chandra Catalogues

Alexander et al. 2003

HDF-N 2Ms (503)

CDF-S 1Ms (326)

Thanks to Mark Allen @ CDS

Results : NEW Type 2 AGN

68 new type 2 AGN candidates

31 have QSO luminosities of Lx>1044 erg s-2

Only 9 previously known in GOODS fields

Now 40 QSO 2s: Quadrupled the QSO 2s in the GOODS fields

QSO 2 numbers higher than predictions

UDF

GOODS

Luminosity distribution

New type 2 AGN

Fills a gap luminosity distrib.

AGN 2 <zest>~2.9

QSO 2 <zest>~3.7

A request for data in the 30' radius centred on the CDFS results in a hierarchical Data Tree for the available data

Data can be loaded directly from the data tree.

Here we load a V-band WFI preview image of the whole CDFS

Local files, scripts and data can be loaded via the MyData panel. Here we load a VOTable file of field centres in the CDFS.

Field of view outlines are interactively drawn while browsing the data tree.

Here we have loaded the GOODS ACS version 1.0 field of view into the stack.

Clicking on the image selects all the releveant data in the tree.

The small blue box represents the outline of the image cutout that will be generated on the fly when the request is submitted.

Multiple images can be loaded simultaneously.

Here we open the F850LP, F775W and F435W (z, i, b) nodes of the tree in order to obtain image cutouts from these 3 bands.

The VizieR catalogs panel provides an interface to catalog information.

Here we request a catalog of X-ray sources from Alexander et al

Catalog points are overlaid on the image.

Column metadata such as UCDs and units are displayed

The Column calculator allows generation of new catalog columns

Here we calculate the Hardness Ratio using the hard and soft X-ray count rates from the Alexander catalog

The filters function allows selection of catalog subsets. Here we filter out sources with upper limits in both hard and soft bands

Filters act as a “process” in the stack, applying to all catalog planes below the filter.

The result of a filter may be saved by exporting a plane of the filtered sources

Absorbed sources are selected by a filter that selects sources with hardness ratio > -0.2

The Szokoly et al catalog of redshifts of CDFS sources derived from VLT-FORS spectra is loaded.

The spectra from which the Szokoly catalog was generated are available via a Simple Spectral Access server.

The SSA server is accessed from the VO demo panel

A request for spectral data in the region of the CDFS results in a tree of the available data

The positions of the spectral data, and where possible the slit position angle is drawn on the image.

Spectra may be loaded directly from the data tree

It is also possible to make a catalog plane of the spectral data positions to more clearly link the spectra to the images

Clicking on the spectrum link in the catalog fires up Specview

Here we load the spectrum for the CDF 027 source

CDF 027 is a type 2 QSO (z=3.046) discovered by the CDFS team.

Zooming into the spectral display shows Ly-alpha and CIV emission lines

CDF 011 is an example of a type 1 QSO

A cross-match service for catalog planes is available from the Plugins menu

Cross match of the selected absorbed sources and the Szokoly catalog using a threshold radius of 1.5”

The cross match result consists of a new plane with the joined tables.

For our sources we now have a table with X-ray fluxes and redshifts

Using the cross-match result we now calculate the X-ray luminosity, and corresponding uncertainty

Filter out any sources without redshifts in the Szokoly catalog

The VOPlot tool in the plugin menu allows plotting of columns from catalog planes

Here we plot the X-ray luminosity against the hardness ratio

Error bars may be plotted using the interface in the View menu

The VOPlot 'select points' mode shows the selected points highlighted on the image

Here we show the locations of all the sources with Lx>10^44: our objects of interest:

Type 2 QSO's.

Using VOSpec

IC418

IR from warm dust in remnant

AGB shell

Nebular

radiocontinuum

Hot stellar emission

IC418 - hot uv stellar emission

HD161796 - cooler star

Narrow-band imaging of IC418

Review of VO Client Side Tools

Construct false-colour image

Make use of the HST archive

[N II] (F658N)

Low excitation line

H-alpha (F656N)

[O III] (F502N)

Higher excitation line

Simple over lay of images shows mis-alignment

Due to mismatch in the astrometric reductions

Use of Aladin to enable astrometric alignment

And create the final RGB image ...

Misaligned

Lecture 5: Acknowledgements + Refs

Slides 5-8 describing some new Aladin features from Allen: see http://www.euro-vo.org/internal/Avo/SwgMeeting06/tools.pdf

Slides 26-53 are from Mark Allen and illustrate the 'extragalactic' science case demonstration: see http://www.euro-vo.org/twiki/bin/view/Avo/SwgMeeting04

You can follow that demonstration using the detailed instructions given http://www.euro-vo.org/twiki/bin/view/Avo/ExtragalacticScenario

The science paper (Padovani, Allen, Rosati, Walton, 2004) is at: http://ukads.nottingham.ac.uk/cgi-bin/nph-bib_query?bibcode=2004A%26A...424..545P&amp;db_key=AST&amp;high=412cbd1d6f00525

Slides 54-58 due to Anita Richards – elements of the 'stellar' case from the AVO Jan 2005 demo – see http://www.euro-vo.org/twiki/bin/view/Avo/SwgMeeting06

Other credits as noted in the individual slides.

Next Lecture:
Workflow based demonstrations

vo-lec05-5

VO course - IoA - Feb/Mar 2005 - Lecture 5: Nic Walton

Nicholas Walton

2004-11-10T15:41:41