Source association: XXL case study Sotiria Fotopoulou in association - PowerPoint PPT Presentation

Source association: XXL case study Sotiria Fotopoulou in association with: S. Paltani, L. Chiappetti, M. Brusa, A. Bongiorno, P . Ciliegi and the XXL collaboration

The XXL survey ● 2 x 25 sq. deg. PI: M. Pierre ● 6Ms XMM Newton ● fmux limit : 1e-15 erg/s/cm 2 XXL-N XXL-S ~10 4 X-ray sources ~10 6 optical sources

Multiwavelength SED

Source Detection: nature vs nurture g r i z u Source's physical properties: bluer or Survey properties: exposure, redder, star formation vs absorption seeing, image noise.

X-ray – optical association

How many? multiplicity = N(optical) / N(X-ray)

Likelihood Ratio ● Introduced in Sutherland & Sanders 1992 ● Used regularly in XMM-Newton surveys e.g. COSMOS (Brusa et al., 2005, 2007), Lockman Hole (Rovilos et al., 2010) q(m, c): f(x, y): probablity distribution probablity distribution in magnitude and type function of positional errors n(m,c): surface density per magnitude of background objects

Likelihood Ratio Probability j object is the correct identifjcation Where Q the expected identifjcation rate

Application e.g., Brusa et al., 2005, 2007, Rovilos et al., 2010, Civano et al., 2015 ● Step-by-step per catalog: depth and/or wavelength ● accept gaussian uncertainties ● built appropriate control sample per catalog n(m,c): q(m, c): surface density per probablity distribution magnitude of in magnitude and type background objects

XXL X-ray – optical/IR associations ● Find sources around 3'' from X-ray position ● Create magnitude distribution ● Find magnitude distribution of background sources ● USNO B1.0 catalog: bright unsaturated sources ● CFHTLS/BCS/DECam i/y magnitude ● CFHTLS/BCS/DECam r magnitude ● WIRcam K magnitude ● VISTA K magnitude ● IRAC [3.6]

XXL X-ray – optical/IR associations ● USNO B1.0 catalog: bright unsaturated sources Field galaxies stars all X-ray

Wide area X-ray surveys: XXL-1000-AGN

Wide area X-ray surveys: XXL-1000-AGN

Wide area X-ray surveys: XXL-1000-AGN

Conclusion  As long as the multiplicity is > 1, LR is needed.  Planned X-ray surveys: wide area, not small PSF  counterpart also in catalogs of bright objects  SDSS too “deep” Take home message: – What is the difgerence between theory and pratice? – In theory, they are the same. In practice...