[PPT] - X-ray (and multiwavelength) X-ray (and multiwavelength) surveys PowerPoint Presentation

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X-ray (and multiwavelength) surveys X-ray (and multiwavelength) surveys

Fabrizio Fiore Fabrizio Fiore

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Table of content Table of content

A historical perspective
Tools for the interpretation of survey data
Number counts
Luminosity functions
Main current X-ray surveys
What next
A historical perspective
Tools for the interpretation of survey data
Number counts
Luminosity functions
Main current X-ray surveys
What next

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A historical perspective A historical perspective

First survey of cosmological objects:

radio galaxies and radio loud AGN

The discovery of the Cosmic X-ray

Background

The first imaging of the sources making

the CXB

The resolution of the CXB
What next?
First survey of cosmological objects:

radio galaxies and radio loud AGN

The discovery of the Cosmic X-ray

Background

The first imaging of the sources making

the CXB

The resolution of the CXB
What next?

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Radio sources number counts First results from Cambridge surveys during the 50’: Ryle Number counts steeper than expected from Euclidean universe

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Number counts

Flux limited sample: all sources in a given region of the sky with flux > than some detection limit Flim.

Consider a population of objects with the same L
Assume Euclidean space

n(r) = space density; dN(r) = n(r)dV = n(r)r2drdΩ total number of sources dN(r) dΩ = n(r)r2dr surface density; F = L 4πr2 Flux; F > Flim r

max =

L 4πFlim      

1/2

N(Flim) = dN dΩ

∫

F > Flim

( ) =

dN dΩ

∫

r < r

max

( )

n(r)r2dr

rmax

∫

Total number of sources per unit solid angle (cumulative distribution) Uniform density of objects ⇒ n(r) = n0 N(Flim) = n0 r

max 3

3 = n0 3 L 4πFlim      

3/2

log N(Flim)

( ) = log

n0L3/2 3 4π

( )

3/2

        − 3 2 log Flim

( ) ⇒ α = −1.5

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Number counts

Test of evolution of a source population (e.g. radio sources). Distances of individual sources are not required, just fluxes or magnitudes: the number of objects increases by a factor of 100.6=4 with each magnitude. So, for a constant space density, 80% of the sample will be within 1 mag from the survey detection limit.

( ) ( ) ( )

m . N(m) m F m .

F

F . m 6 log 6 . log 2 3 4 log so log 5 2

lim lim lim

∝ ⇒ = − ∝ − ∝

If the sources have some distribution in L:

n(r,L)drdL = n(r)Φ(L)drdL Φ(L)dL ≡ Luminosity Function N(r) = n(r,L)r2drdL =

rmax(L)

∫ ∫

n0 3 4πFlim

( )

−3/ 2

L3/2

∫

Φ(L)dL

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Problems with the derivation of the number counts

Completeness of the samples.
Eddington bias: random error on mag measurements can alter the number
counts. Since the logN-logFlim are steep, there are more sources at faint

fluxes, so random errors tend to increase the differential number counts. If the tipical error is of 0.3 mag near the flux limit, than the correction is ∼15%.

Variability.
Internal absorption affects “color” selection.
SED, ‘K-correction’, redshift dependence of the flux (magnitude).

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Galaxy number counts

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Optically selected AGN number counts

z<2.2 B=22.5 ∼100 deg-2 B=19.5 ∼10 deg-2 z>2.2 B=22.5 ∼50 deg-2 B=19.5 ∼1 deg-2 B-R=0.5

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X-ray AGN number counts

<X/O> OUV sel. AGN=0.3 R=22 ==> 3×10-15 ∼1000deg-2 R=19 ==> 5×10-14 ∼25deg-2 The surface density of X-ray selected AGN is 2-10 times higher than OUV selected AGN

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The cosmic backgrounds energy densities

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The Cosmic X-ray Background The Cosmic X-ray Background

Giacconi (and collaborators) program: 1962 sounding rocket 1970 Uhuru 1978 HEAO1 1978 Einstein 1999 Chandra!

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The Cosmic X-ray Background The Cosmic X-ray Background

The CXB energy density:
Collimated instruments:
1978 HEAO1
2006 BeppoSAX PDS
2006 Integral
2008 Swift BAT
Focusing instruments:
1980 Einstein 0.3-3.5 keV
1990 Rosat 0.5-2 keV
1996 ASCA 2-10 keV
1998 BeppoSAX 2-10 keV
2000 RXTE 3-20 keV
2002 XMM 0.5-10 keV
2002 Chandra 0.5-10 keV
2012 NuSTAR 6-100 keV
2014 Simbol-X 1-100 keV
2014 NeXT 1-100 keV
2012 eROSITA 0.5-10 keV
2020 IXO 0.5-40 keV
The CXB energy density:
Collimated instruments:
1978 HEAO1
2006 BeppoSAX PDS
2006 Integral
2008 Swift BAT
Focusing instruments:
1980 Einstein 0.3-3.5 keV
1990 Rosat 0.5-2 keV
1996 ASCA 2-10 keV
1998 BeppoSAX 2-10 keV
2000 RXTE 3-20 keV
2002 XMM 0.5-10 keV
2002 Chandra 0.5-10 keV
2012 NuSTAR 6-100 keV
2014 Simbol-X 1-100 keV
2014 NeXT 1-100 keV
2012 eROSITA 0.5-10 keV
2020 IXO 0.5-40 keV

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The V/Vmax test

Marteen Schmidt (1968) developed a test for evolution not sensitive to the completeness of the sample. Suppose we detect a source of luminosity L and flux F >Flim at a distance r in Euclidean space:

r = L 4πF      

1/ 2

the same source could have been detected at a distance r

max =

L 4πFlim      

1/ 2

So we can define 2 spherical volumes: V = 4πr3 3 ; Vmax = 4πr

max 3

3

If we consider a sample of sources distributed uniformly, we expect that half will be found in the inner half of the volume Vmax and half in the outer

half. So, on average, we expect V/Vmax=0.5

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The V/Vmax test

V = 4πr3/3

( )

rmax

∫

Ω

∫

n(r)r2drdΩ n(r)r2drdΩ

rmax

∫

Ω

∫

= 4πn0 3 r5dr

rmax

∫

n0 r2dr

rmax

∫

= 4π 3 r

max 6 /6

r

max 3 /3 = 4π

3 r

max 3

2 so : V Vmax = 0.5

In an expanding Universe the luminosity distance must be used in place

f r and rmax and the constant density assumption becomes one of

constant density per unit comuving volume .

∑

=

N i i i

z V z V V V

1 max max

) ( ) (

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Luminosity function

In most samples of AGN <V/Vmax> > 0.5. This means that the luminosity function cannot be computed from a sample of AGN regardless of their z. Rather we need to consider restricted z bins.

max max

1 ) ( : sample limited volume a from drawn are sources the If V N V l L

L

= = Δ Φ

∑

More often sources are drawn from flux-limited samples, and the volume surveyed is a function of the Luminosity L. Therefore, we need to account for the fact that more luminous objects can be detected at larger distances and are thus over-represented in flux limited samples. This is done by weighting each source by the reciprocal of the volume over which it could have been found:

∑

= Φ

i i z

V dL z L ) ( 1 ) , (

max

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Luminosity function 1/Vmax method or maximun likelihood method: ? = ∏i=1

N

Ω(Li)dzdL ? j dV dz dz Φ(L)dL

∞ Llim

j (z)

∫

z1 z2

∫

j

∑

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Assume that the intrinsic spectrum of the sources making the CXB has αE=1 I0=9.8×10-8 erg/cm2/s/sr ε’=4πI0/c

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Optical (and soft X-ray) surveys gives values 2-3 times lower than those obtained from the CXB (and of the F.&M. and G. et al. estimates)

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Flux 0.5-10 keV (cgs) Area

HELLAS2XMM 1.4 deg2 Cocchia et al. 2006 Champ 1.5deg2 Silverman et al. 2005 XBOOTES 9 deg2 Murray et al. 2005, Brand et al. 2005

XMM-COSMOS 2 deg2

16
15
14
13

CDFN-CDFS 0.1deg2 Barger et al. 2003; Szokoly et al. 2004 EGS/AEGIS 0.5deg2 Nandra et al. 2006

SEXSI 2 deg2 Eckart et al. 2006

C-COSMOS 0.9 deg2

E-CDFS 0.3deg2 Lehmer et al. 2005 ELAIS-S1 0.5 deg2 Puccetti et al. 2006

Pizza Plot

A survey of X-ray surveys A survey of X-ray surveys

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A survey of X-ray surveys A survey of X-ray surveys

Point sources Clusters of galaxies

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A survey of surveys A survey of surveys

Main areas with large multiwavelength coverage:

CDFS-GOODS 0.05 deg2: HST, Chandra, XMM, Spitzer,

ESO, Herschel, ALMA

CDFN-GOODS 0.05 deg2: HST, Chandra, VLA, Spitzer,

Hawaii, Herschel

AEGIS(GS) 0.5 deg2: HST, Chandra, Spitzer, VLA, Hawaii,

Herschel

COSMOS 2 deg2: HST, Chandra, XMM, Spitzer, VLA, ESO,

Hawaii, LBT, Herschel, ALMA

NOAO DWFS 9 deg2 : Chandra, Spitzer, MMT, Hawaii, LBT
SWIRE 50 deg2 (Lockman hole, ELAIS, XMMLSS,ECDFS):

Spitzer, some Chandra/XMM, some HST, Herschel

eROSITA! 20.000 deg2 10-14 cgs 200 deg2 3×10-15 cgs

Main areas with large multiwavelength coverage:

CDFS-GOODS 0.05 deg2: HST, Chandra, XMM, Spitzer,

ESO, Herschel, ALMA

CDFN-GOODS 0.05 deg2: HST, Chandra, VLA, Spitzer,

Hawaii, Herschel

AEGIS(GS) 0.5 deg2: HST, Chandra, Spitzer, VLA, Hawaii,

Herschel

COSMOS 2 deg2: HST, Chandra, XMM, Spitzer, VLA, ESO,

Hawaii, LBT, Herschel, ALMA

NOAO DWFS 9 deg2 : Chandra, Spitzer, MMT, Hawaii, LBT
SWIRE 50 deg2 (Lockman hole, ELAIS, XMMLSS,ECDFS):

Spitzer, some Chandra/XMM, some HST, Herschel

eROSITA! 20.000 deg2 10-14 cgs 200 deg2 3×10-15 cgs

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40 arcmin 52 arcmin z = 0.73 struct ure z-COSMOS faint Color: XMM first year Full COSMOS field

Chandra deep and wide fields Chandra deep and wide fields

CDFS 2Msec 0.05deg2 CCOSMOS 200ksec 0.5deg2 100ksec 0.4deg2 ~400 sources 1.8 Msec ~1800 sources Elvis et al. 2008 20 arcmin 1 deg

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XMM surveys XMM surveys

COSMOS 1.4Msec 2deg2 Lockman Hole 0.7Msec 0.3deg2

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Chandra surveys Chandra surveys

AEGIS: Extended Groth Strip Bootes field

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Spitzer large area surveys: SWIRE Spitzer large area surveys: SWIRE

Elais-N1 Elais-N2 XMM-LSS Elais-S1 Lockman Hole

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eROSITA eROSITA

~30ks on poles, ~1.7ksec equatorial

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What next? The X-ray survey discovery space What next? The X-ray survey discovery space

13 -15 -17 cgs

log Sensitivity log Energy range 1 10 100 keV L

g

A r e a d e g

2

4 2

Einstein Einstein ROSAT ROSAT ROSAT ROSAT eROSITA eROSITA ASCA/BSAX ASCA/BSAX XMM XMM Chandra Chandra IXO IXO IXO IXO NS NeXT NS NeXT SX SX BSAX/ASCA BSAX/ASCA XMM XMM Swift Swift