Astronomical spectroscopy and the Virtual Observatory: a user-oriented perspective

ESAVO/European Space Astronomy Centre (ESAC)Villafranca del Castillo, MADRID (SPAIN)Matteo Guainazzi“Astronomy with Virtual Observatories”

Pune, 17 October 2007

Astronomical spectroscopy and the Virtual Observatory: a user-oriented perspective

Matteo Guainazzi1, Andrea Laruelo, Jesus Salgado, Isa Barbarisi, Pedro Osuna

ESA-VO, Science Operations DepartmentEuropean Space Astronomy Center of ESA

Villafranca del Castillo, Spain

1also EURO-VO astronomer



Outline

Why do we care?• Spectroscopic surveys in the past and in the future

Which added value can VO bring to the analysis of spectroscopic data?

What does the VO currently offer?• Data models• Data access protocols• Spectral services• Spectral VO applications

Adds-on• Access to atomic and molecular lines databases• Access to theoretical models



Spectroscopic surveys: the past

Number of redshifts in surveys as a function of time

(Yip et al. 2007)

Year Number R z Magnitude Limit

FBS 1965 2x106 1800 V<17.5

SBS 1991 3x106 280-1800

V<19

Case 1995 1350 V<18

HQS 1997 2x103 1390 0 to 3.5 V<19

HES 1996 1.5x103 280 1.5 to 3.2 V<18

LCRS 1994 2.5x104 1000 0 to 0.2 R<17

2dF 1998 2.5x104 0 to 2.2 b<21

SDSS 2000 106 2000 0 to 0.3 r < 17.77 (galaxies)

105 2000 0 to 6 r < 19.1 (quasars)

DEEP2 2002 5x104 5000 0.7 to 1.5 I < 24

VVDS 2002 1.5x105 250 0.2 to 4.0 I < 22.5

5x104 250 0.2 to 4.0 I < 24

103 250 0.2 to 4.0 I < 26

zCosmos 2005 2x104 600 0.1 to 1.2 I < 22.5

2x104 230 1.4 to 3.0 color selection



Evolution of survey source numbers

(Cro

pper

200

7)



What do we gain with the VO?

We should be able to largely gain in efficiency (from “it would take my whole lifetime to do it” to “it can be done by my Ph.D. student”) for tasks like:

Building spectral energy distributions (spectra+photometry) by combining large datasets from different sources

Comparing spectra and images (footprint, contamination …) Analysis and clever visualization of large datasets Correlation of spectrally-derived parameters from different sources Automatic classification (and outliers discovery) Multi-parameter connectedness (M.Cropper) Selection of sub-samples on the basis of a multi-parameter space Access to ancillary information useful for the interpretation of the data: existing

object classification, publications



What should VO tools be also able to do?

Basic display tools: superposition, rebinning, smoothing, dynamical spectra Radial velocity measurements and superposition of spectral region in the velocity

parameter space Rectification Fits (Gaussian, Maxwellian, Voigt profiles) Measurement of line profile asymmetry and broadening Time analysis (periodograms, Fourier analysis, Doppler imaging) Spectral deconvolution in energy and Fourier space Comparison between observed spectra and spectral templates Comparison between observed spectra and theoretical models

Not all functionalities must be simultaneously present in a given tool!



What does the VO offer?

Data models and data access protocols:

• Simple Spectral Access (SSA; Tody et al. 2007)• Based on the concept of a “1-D” spectrum: spectral coordinates, flux, error,

quality flag, etc,

• Virtual data generation: cut-out, reprojection, dynamic extraction etc.

• Support to multiple data format: VOTable, FITS binary, CSV, native XML, HTML

• Spectrum Data Model (Mc Dowell et al. 2007) Spectral services Applications

• Specview (STScI)

• SPLAT (AstroGrid)

• VOSpec (ESA-VO)



What does the VO offer?

Data models and data access protocols:

• Simple Spectral Access (SSA; Tody et al. 2007)• Based on the concept of a “1-D” spectrum: spectral coordinates, flux, error,

quality flag, etc,

• Virtual data generation: cut-out, reprojection, dynamic extraction etc.

• Support to multiple data format: VOTable, FITS binary, CSV, native XML, HTML

• Spectrum Data Model (Mc Dowell et al. 2007) Spectral services Applications

• Specview (STScI)

• SPLAT (AstroGrid)

• VOSpec (ESA-VO)



EURO-VO spectroscopic tools

SPLAT-VOVOSpec

http://star-www.dur.ac.uk/~pdraper/splat/splat-vo/splat-vo.html

http://esavo.esa.int/vospecapp



Basic working scheme

Collectspectra

BuildSED

• Local files• Remote servers

Preparespectra

• Data screening• Rebinning• Filtering• De-noising• De-reddening• Units conversion• Spectra arithmentic• Convolutions

Analysespectra

• EW• Flux• Fit• Bisectoring• Mirroring• Interpolation• Line identification• Theory

Publishresults

• Paper-quality plots• Export analysis

• Units?



SED generation and graphics

Access to spectra from:• Local files (FITS, ASCII, NDF …)• Files available on the Internet• Simple Spectral Access Protocol compatible servers:

• (CDF-S, EUVE, FUSE, Giraffe, HST, HUT, Integral/OMC, ISO, IUE, SDSS, XMM-Newton/RGS, WHS, WUPE …)

Units handling• Most of the standard units on the frequency/energy/wavelength axis, and on

the flux density axis can be hadled automatically• VOSpec also handles automatically any units via dimensional analysis

Plotting• Single- and multi-spectra plotting, with various standard graphical facilities• SPLAT allows the co-existence of different plotting windows, a “drag the

file name” function to display a new spectrum, and movie generation• VOSpec allows interactive mouse-driven zooming



Analysis tools: SPLAT

• Conversion to velocity, redshift or Lorentz factor space

• Spectral arithmetic for spectra (limited to strictly overlapping frequency ranges)– Pairs of spectra– Spectra and a constant

• Cut and removal of spectral ranges• Fit of continua and emission/absorption

lines• Generation of a spectrum from an

interpolated line (needed to evaluate the continuum level underneath a fitted line)

• Filtering• Flipping/translating • SPEFO (legacy software from Ondřeov

Observatory)



VOSpec: spectral analysis functionalities I.

• Arithmetic and convolution between spectra

• Line fitting

• Best Fit of theoretical models

Fit of theoretical models to an observed spectrum (see later)

Fit of an absorption line profile with different models

(Gaussian, Loretntzian Voigt)



VOSpec: spectral analysis functionalities II.

• Mirroring, bisector

• Interactive integrated flux and equivalent width

• Filtering

• Discrete wavelet analysis

• Wavelength-to-velocity conversion

• Dereddening:• Calzetti law• Cardelli-O’Donnel law• LMC law

• Calculation of luminosity differences between observational spectra and models



The power of interoperability I.

GB2MASS SDSS

ROSATChandra

AstroScope: catalogue search

Aladin: multipanel imaging

VOSpec: generation of SEDsTOPCAT: tabular data plotting/manipulation



Community efforts I.: EZ and GOSSIP

EZ:Automatic calculation of

spectroscopic redshifts

GOSSIP:Spectrophotometric analysis

through SED fitting (not VO yet)

http://cosmos.iasf-milano.inaf.it/pandora

(Franzetti 2007; Garilli 2007)



Simple Line Access through VOSpec

• VOSpec provides access to atomic and molecular line Databases throuh a specific VO access protocol (SLAP):– NIST– CHIANTI (X-rays)– CIELO (XMM-Newton)– IASD (ISO)– LERMA (molecular)

• This allows on-the-fly identification of transitions associated to a given observed feature

• SPLAT includes a hardcoded line identification facility on the basis of standard sets of lines



Easy access to theoretical models (TSAP)

SVO web server implementation(http://svo.laeff.inta.es) ESA-VO VOSpec implementation



Thoretical models fit step by step

Selecting TSA server

Initial model

Best fit model

minimizationproccess

Select TSA server

Select initial parameters



A typical session …



Will we ever have X-ray data in the VO?

• Traditional wisdom: no!• Spectra in X-ray archives

are in instrumental counts• Conversion into physical

units is strongly model dependent due to non-linearity of the redistribution matrix

• “We” X-ray astronomers know how to do it: ask us!

Little, little, twinkling star …

?

XMM-Newton EPIC redistribution function



Yes! XMM-Newton/RGS

• However, high-resolution instruments are now flying: XMM-Newton RGS (R≈300-1800)

• The redistribution function is very close to linear

• Model independent fluxed spectra can be produced

• Soon availabe as VO server (the first all-sky spectral X-ray server ever)

– Pilot project on Seyfert 2 galaxies available since 1 year (CIELO-AGN)

• No general solution yet for moderate-resolution spectra (XMM-Newton/EPIC, Chandra/ACIS, Suzaku/XIS, Swift …)

RGS redistribution function

(Gonzalez-Riestra & Rodriguez-Pascal 2007)

ABDor



Conclusions: wher do we stand?

On-the-fly SED generation: Spectra access from SSAP-compatible server Automatic handling of units

Spectral analysis tools Growing suite of spectral analysis tools available in the “mainstream” tools Multi-component fit possible Community-based web-services start appearing for more specialized tasks

Interoperability All tools use PLASTIC First steps to export via PLASTIC also the analysis results

Usage on massive sets of data

Mainly designed to handle one source at the time → highly interactive



(Bra

ndt e

t al.

2001

)

Science highlight from spectroscopic surveys

(Le

Fèvr

e et

al.

2006

)

VVDSDiscovery of high-redshift dusty galaxy population with strong star formation

SDSSHigh-redshift QSOs

XMM-Newton

SDSS: New stellar streams and satellites of the Milky Way(B

elok

urov

et a

l. 20

06)

SDSS, z~0.1

DEEP2, 0.75<z<1.05

SDSS+DEEP2Red galaxy environment

(Cooper et al. 2006)

Documents

Astronomical spectroscopy and the Virtual Observatory: a user-oriented perspective