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Radio Surveys

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5.0 GHz Area=6 sr Slim 30 mJy N 55000 GB6 (Gregory et al. 1996) ... 0.8 GHz Area=7900 deg2 Slim 6-10 mJ N. 2x105 NVSS (Condon et al. 1993, 1998) ... – PowerPoint PPT presentation

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Title: Radio Surveys


1
Radio Emitting AGNs Statistical Studies I.
Prandoni
  • Radio Surveys
  • Radio Counts
  • Luminosity Function
  • Evolution
  • Modeling the faint radio sky

2
Statistical Studies Surveys
  • Various source populations ? average properties
    - Cosmological evolution ? average properties
    vs. z ev. of single
    objects not possible- Rare objects -
    Serendipitous discoveries ? new classes of objs-
    Source catalogues ? ad hoc samples


3
Why Radio Surveys?
Advantages of radio band ? feasible from the
ground (like optical)? observing day and
night? scarsely sensitive to atmospheric
variations? complete samples no dust/IGM
extinction and/or gas obscuration

4
Why Radio Surveys?
Advantages of radio observing techniquesFOV ?
?/D small aperture ? larger FOV ?
interferometry ? ? ?/d high resolution
? lower confusion limit good position
accuracy ? ? ND2
large N ? better rms ? mosaicing (gt90s)
efficient technique to cover
large areas of sky
with uniform rms
(mainly at radio ?s)

Nobeyama Millimeter Array
5
Mosaicing Technique theory
Mosaicing ? combination of regularly spaced
multiple pointings linearly
combined to produce an image larger than
telescopes primary beam (FOV)
  • Intensity distr. (or Brightness) in final mosaic
    I(l,m)
  • ? weighted average of pixels in
    individual pointings
  • Weights ? primary beam response expected noise
  • If same obs. param. and cond. ? pointing Pi
    (l,m) ? ?i 2 ? 2
  • I(l,m) modulated only by primary beam response

Sault Killeen 1995
Ii(l,m)? Brightness of i-th pointing
6
Mosaicing Technique theory
Mosaicing experiment Main Issue pointing
grid pattern (geometry spacings) Limit on
spacings from Nyquist theorem To recover full
information ? srett ? ???D
? shex ? 2??? ? ???D To get uniform noise
over the mosaic I ? ?(I)
?/?(? Pi2) const. ?(I)/? 1/?(? Pi2)
const. ?i
?
7
Mosaicing Technique theory
A SIMPLE CASE ? Two Pointings
P1(0), P2 (s) ? Circular Gaussian Primary
Beams Pi(r) exp-4
ln2 (r/FWHM)2 Pi2(r)
exp-4 ln2 (r/FWHM/?2)2
? Pi'(r) with FWHM FWHM/?2
?s/FWHM
? (P'1 P2)
8
Mosaicing Technique simulations
ATCA D22 m ?20 cm FWHM 33
arcmin FWHM FWHM/?2 23.33 arcmin
Sensitivity over 1 sq.deg. ?(I)/? 1/?(?
Pi2) ? Contours 5, 10, 20,
Rectangular Grid 4x4 pointings
s23.33 arcmin
9
Mosaicing Technique simulations
?(I)/?i 1/?(? Pi2) ? Contours 5, 10,
20, Sensitivity over 1 sq.deg.

Hexagonal Grid 22 pointings
s20 arcmin
For comparison Nyquist _at_ ATCA ? shex ?
19.6 arcmin
10
Mosaicing Technique simulations
?(I)/?i 1/?(? Pi2) ? Contours 5, 10,
20, Sensitivity over 1 sq.deg.

Rectangular Grid 4x4 pointings
s20 arcmin
For comparison Nyquist _at_ ATCA ? srett ?
17 arcmin s20 only for point source det.
experiments
11
Major Large Scale Radio Surveys
Slim gt 100 mJy
3CR (Bennett et al. 1962, Laing et al. 1983) ?
?178 MHz Area6 sr Slim? 9 Jy N ? 3504C
(Pilkington Scott 1965, Gower et al. 1967) ?
?178 MHz Area6 sr Slim? 2 Jy N ? 1000
8C (Rees 1990) ? ?151 MHz Area0.8 sr
Slim? 1 Jy N ? 5000 MOLONGLO (Large et al.
1981) ? ?408 MHz Area8 sr Slim? 700 mJy N
? 12000 B2 (Colla et al. 1970, 1972, 1973, Fanti
et al. 1974) ? ?408 MHz Area2 sr Slim? 200
mJy N ? 10000 PKS (Wall et al. 1971 and
following papers) ? ?2.7 GHz Area7 sr
Slim? 200 mJy N ? 17000B3 (Ficarra et al. 1985)
? ?408 MHz Area1 sr Slim? 100 mJy N ?
13000
12
Major Large Scale Radio Surveys
1 mJy lt Slim lt 100 mJy
87GB (Gregory Condon 1991) ? ?5.0 GHz
Area6 sr Slim? 30 mJy N ? 55000 GB6 (Gregory
et al. 1996) ? ?5.0 GHz Area6 sr Slim? 18
mJy N ? 75000WENSS (Rengelink et al. 1997) ?
?325 MHz Area3 sr Slim? 15 mJy N ?
2x105SUMSS (Mauch et al. 2003) ? ?0.8 GHz
Area7900 deg2 Slim? 6-10 mJ N?2x105 NVSS
(Condon et al. 1993, 1998) ? Area10 sr Slim?
2.5 mJy N ? 2x106FIRST (Becker et al. 1993,
White et al. 1997) ? Area3 sr Slim? 1 mJy
N ? 9x105
MOSAICS
13
Best Studied Deep Radio Fields
Slim lt 1 mJy _at_ 1.4 GHz
Marano Field (Gruppioni et al. 1997) Slim
0.2 mJy Area 0.36 deg2 LBDS (Windhorst et
al. 1984) Slim 0.1-0.2 mJy Area 5.5
deg2 Lockman Hole (de Ruiter et al. 1997)
Slim 0.12 mJy Area 0.35 deg2 Lynx 3A (Oort
1987) Slim 0.1 mJy Area 0.8
deg2 085217 (Condon Mitchell 1984) Slim
0.08 mJy Area 0.32 deg2 130030 (Mitchell
Condon 1985) Slim 0.08 mJy Area 0.25
deg2 HDF North (Richards 1999) Slim 0.04
mJy Area 0.3 deg2
Typically Nlt100 RS
14
Source Counts
Survey ? catalogue of sources ? source counts
vs.S (or mag) logN logS or logN
log m Integral counts N(gtS) num. of sources
per area unit (sr or
deg2) with flux gtS Differential
counts N(S) num. of sources per area unit with
flux between S and
SdS Source counts ? simplest
cosmological tool to constrain a) source
cosmological evolution b) contribution of
different galaxy types to global population
c) Universe geometry (in principle) Comparison
between Observed Modeled source counts
15
Theory of Source Counts
  • Simplest source count model ? non-ev. static
    Euclidean Universe
  • ?L ? N(gtS) ?(L) V
  • ?(L) uniform volume density of sources with
    luminosity L
  • V 4/3 ?d3 volume over which the sources
    have flux gtS

  • NB dd(L)
  • ?L SL/(4?d2 ) or dL/(4?S)1/2
  • N(L,gtS) ? 4/3? d3 ? 4/3? L/(4?S)3/2 ? ?(L)
    L3/2 S-3/2
  • NB If ?(L) ? L-3/2 Critical LF ?
    N(L,gtS) N(gtS) ? S-3/2 only
  • Summing over L Ntot(gtS) ? ?L ?(L) L3/2 S-3/2
  • and N(S) d N(gtS) /dS ? S-5/2 ? N(gtS) ?
    S-3/2 N(S) ? S-5/2

16
Theory of Source Counts
Beyond Local Universe ? relativistic expanding
Universe a) expansion dmax ? luminosity
distance dL In a E-dS, ?0, ?1 ? dL
dc (1z) dc comoving distance ?
SL/4?dc2(1z)2 ? For given S L ? dc2 lt
static Eucl. b) geometry curved space-time
(Robertson-Walker metric) ? dVsr r2dr /
(1-kr2)1/2 where k 0,1,-1 NB only
when k0 (flat Universe) ? Vsphere (Euclidean
case) For any standard cosmological models
?N(gtS) ? S-?(S) where ?lt3/2 and ?
3/2 for S ?? Counts flatter than for static
Eucl. case at decreasing S
17
Theory of Source Counts
?(L) uniform
NB Total N(S) dictated by ?(L) ?(L) defines
the proportion in which curves for each L added
to total
18
Introducing Evolution
Only assuming comoving source density not
constant we can get N(S) steeper than Euclidean
? ?(L) ?0 r? where ???
N(L,gtS) ?0rdN ? ?0r r ?? dr ? S (??1)
If evolution dominates the counts shape ?
Universe geometry cannot be determined
19
Observed Radio Source Counts
Normalized Counts _at_ 1.4 GHz log S 5/2 N(S)
II
III
I
IV
V
I - Euclidean Region ? Local bright RS II -
Steep Rise ? N(gtS) ? S(1.8-1.9) (AGN LF ev.) III
- Euclidean Region ? differential LF evolution
IV - Convergence Region ? N(gtS) ? S(0.5-0.8) to
1 of Eucl.value

(cutoff _at_ z2-3) V - Euclidean Region ?
new population of RS (SFG)
log S (Jy)
20
Evolutionary Source Counts Models
To build source count models ? 4 main
ingredients 1) cosmology 2) LF 3) SED 4)
evolution Two basic types of source count model
forward backward Forwards method (ab
initio) statistically follows the growth of dark
matter halos forwards in time by accretion and
mergers, in a given galaxy formation paradigm and
evolutionary framework Backwards method local
F(L) evolved backwards in time, assuming
arbitrary form of evolution Radio Source Counts ?
traditionally backwards method (closely tied to
obs., few free parameters, but no physical
meaning) NB not clear why only 10 of AGNs are
radio-loud
21
Radio Luminosity Function
F(L)dL or F(P)dP ? density of sources (per Mpc3)
with radio
power between P and PdP To get F(P)dP ? RS
identification and redshift measurement Not easy
? only 3CR complete id. and z (Bright Es at
z?1-2) S-z relation does not hold for radio-AGNs
Redshift distribution peaks at z1-2 Backwards
approach ? Local LF evolution
22
Local Radio Luminosity Function
Two components Classical Radio-Loud AGN -
flat LF over 5 orders of mag (close to
critical LF ? any DS samples same DL) -
knee at log P ? 24.5 (W/Hz) (FRI vs
FRII/QSO) - LF ? Double Power Law Star
Forming Galaxies - steep LF - log P
lt 24.5 (W/Hz) - overcome AGNs at
log P lt 23 (W/Hz) - LF ? Power Law Exp.
Power Law Gaussian Exp.
Recent Determination of F(P)dP at 1.4 GHz
(Schechter et al. 1976)
(Saunders et al. 1990)
23
SED ? K correction
Spectral Energy Distribution for Arp220
Radio frequency range
Barger et al. 2000
Steep RS ? a ? -0.7 (FRI/FRII) Flat RS ? 0lt a
lt -0.5 (BLLac/QSO)
Effect of z on observed spectrum
24
Evolution of RLF
Two possible scenarios PLE ?
horizontal translation of local LF PDE ?
vertical translation of local LF
  • Narrow peak of N(S)/No
  • wide AGN LF
  • both PLE PDE rejected
  • LDDE (Longair 1966)
  • only brightest sources evolve
  • 3CR ? high-P QSO/FRII
  • stronger DE (Spinrad et al. 85)
  • 3C ? FRI no or little ev. (Laing et al. 83) but
    questioned!

25
Evolution of RLF
Evolution Functions for Radio-AGNs (99 _at_ Sgt60
mJy) typically LE two
sub-populations a) steep flat RS
(Dunlop Peackock 1990) b) FRI FRII RS
(Jackson Wall 1999) a) DP90 ? LD Double
Power Law F(P,z) dexp -k
(P/Pc)?(P/Pc)ß where PcPc(z)
log Pc (z) az2 bz c
?, ß,
a,b,c differ for steep flat Can reproduce
N(z) at mJy level decline between 2ltzlt5
26
Evolution of RLF
b) JW99 ? LD Exp. function redshift cut-off
F(P,z) expM(P)t(z) where t(z) ?
look-back time
M(P) ? LD factor 0
for PltP1
Mmax
for P1?P ?P2
Mmax
for PgtP2
redshift cut-off F
F(P,z) for z lt zc
F F(P, zc-z) for zc/2 lt z lt zc
F 0
for zgt zc
P1,P2,Mmax,zc ? differ for FRI FRII
FRII strong ev. FRI no ev. ? dramatic decline
of BL-FRII at S? 1 mJy (but evidence of sub-mJy
QSO)
27
Evolution of RLF
Evolution Functions for SFGs two
sub-populations not ev. normal Spirals ? local
RLF strongly
ev. Starburst gals for SB ev. F(P,z)g(z) x
F(P/f(z),z0)
where g(z) ? density ev.

f(z) ? luminosity ev. typically ev.
functions of the form
f(z)? (1z)Q and g(z) ?
(1z)P PLE preferred Q ? 3 P?0 (but see P6.7
Rowan-Robinson 93)
28
Evolution of RLF
  • Non parametric approach 2 arbitrary ev.
    functions
  • F(P,z) g(z) x F(P/f(z),z0) where g(z) ?
    density ev.

  • f(z) ? luminosity ev.
  • (Condon et al. 1984)
  • No distinction between bright and faint sources
  • Can be used for any type of source
  • (applied to both AGN and Star Forming
    Galaxies)
  • NB for SFGs Local LF ? Radio or FIR LF

  • (see Saunders et al. 90)
  • thanks to Radio/FIR corr

29
Radio/FIR Correlation
SDSS
  • SFG
  • Remarkably tight FIR/radio correlation
  • radio luminosity
  • ? nearly proportional to SFR
  • ? nearly independent of B and other
    parameters.

Yun et al. 2002
30
Radio/FIR Correlation
  • SFG
  • Remarkably tight FIR/radio correlation
  • rescaled FIR (dashed curve) and radio (solid
    curve) local LFs of SFGs coincide.
  • FIR and radio imply the same recent SFRD..

31
Radio/FIR Correlation
Holds up to z1
SDSS, Yun et al. 2002 Local Sample
Spitzer FLS, Appleton et. al. 2004
32
The Promise of Deep Radio Fields
  • If sub-mJy sources are mainly SFGs
  • Deep Radio Samples can be used to derive
  • SFH of the universe

Advantages higher res. than FIR
complete unbiased view (no dust
extinction) Dust enshrouded SFH up to high z

33
Largest Deep Radio Mosaics
ATESP (Prandoni et al. 2000a,b) Slim 0.47
mJy Area 26 deg2 N ? 3000 ELAIS
S (Gruppioni et al. 1999) Slim 0.4 mJy Area
4.0 deg2 PDF (Hopkins et al. 1998, 2003) Slim
0.06 mJy Area 4.6 deg2 N ?
2000 ELAIS N (Ciliegi et al. 1999) Slim
0.135 - 1.15 mJy Area 0.12 - 4.22 deg2
VLA-VVDS (Bondi et al. 2003) Slim 0.08 mJy
Area 1.0 deg2 N ? 1000 VLA-COSMOS
(Schinnerer et al. 2007) Slim 0.05 mJy Area
2.0 deg2 N ? 3500 FIRST LOOK
Survey (Condon et al. 2003, Morganti et al
2004) Slim 0.04-0.1 mJy Area 1-5 deg2 N
? 1000-3500
34
A New Look at Radio Counts
NATURE/EVOLUTION of sub-mJy RS Low L/high z
AGN, SB, Ell. Fractions? F(L) ? N(z) ?
SHARP STEEPENING _at_ Slt1 mJy
SF dominates at ?Jy fluxes ETS important at
sub-mJy mJy fluxes e.g. Richards et al. 99,
Gruppioni et al. 99, Haarsma et al. 00, Prandoni
et al. 01b, 02, Gruppioni et al. 03, Sullivan et
al. 04, Ciliegi et al. 05, Fomalont et al. 06
No Change in slope down to 10 µJy
35
Composition of the sub-mJY population
Prandoni et al. 2001b
Radio to Optical Ratio R S x 100.4mag-12.5
(Condon 80) Rgt100 ? AGN/ETS
Rlt100 ? SFGs SF dominates _at_ low R AGN/ETS
dominate _at_ high R
ATESP-EIS
  • Early-type gals important at sub-mJy fluxes
  • Selection effects explain discrepancies among
    sub-mJy samples

36
Composition of sub-mJY population
SBSp CONTRIBUTION TO 1.4 GHz COUNTS
ELAIS S SB Spirals a) L15 k L1.4 GHz
b) mod.ev.per n(S15 ) ? n(S15 ) ? n(S1.4GHz)
Gruppioni et al. 2003
Contribution of MIR SBSp to n(S1.4 GHz )
10 _at_ S0.5-1 mJy gt60 _at_ Slt0.05-0.1 mJy
  • Nuclear processes dominate _at_ Sgt0.5 mJy?

37
A New Look to Radio Count Models
A - Classical RL-AGNs ? lum. ev.
?steep/flat (e.g. DP90) ?FRI/FRII (e.g. JW99)
B - SF gals. ? PLE ? local F(L) L
(1z)p p3 up to zmax then LL(zmax)
(e.g. Condon 89, Saunders et al. 90,
Machalski Godlowski 00, Yun et. al 01,
Sadler et al. 02) C Radio-Quiet AGNs
Rlt1-10 (Jarvis Rawlings 2004)
1.4 GHz Source Counts
38
A Radio-quiet AGN Component
hard X-ray LDDE LF Ueda et al 2003
log(Lx)-4.57 1.012 log(L1.4GHz) Brinkmann
et al. 2000

RQQ Radio 1.4 GHz LF
39
A Radio-quiet AGN Component

Observational characterization
RQ-QSO Kukula et al. 1998 ? radio em. from
optically selected RQQ (Mvlt-23) RS ?compact
steep (ltlt10 kpc, a1.48.4 -0.7 ) 22lt
log(L1.4GHz)lt24 host galaxy ? disk/spheroidal
(em. line spectrum) LDDE (Jarvis
Rawlings 2004) ? largest component at zlt1
  • Ideal Samples 0.5ltSlt5 mJy ? ideal to study the
    low-luminosity AGN component and infer its
    physical properties evolution
  • low/high accretion rates? (FRI vs. RQQ)
  • lower L AGNs peak at lower z?
  • NB LDDE recently found for opt/X-ray AGNs
    Bongiorno et al. 07 Ueda et al. 03 Hasinger et
    al. 05 see also Vigotti et al. 03 Cirasuolo et
    al. 06 for radio AGNs

40
The New Promise of sub-mJy Samples

Assessing Low-Power AGNs Physical properties and
Evolution
  • Ideal samples ? Sgt0.5 mJy
  • low/high accretion rates? (FRI vs. RQQ)
  • lower L AGNs peak at lower z? Type I II AGNs
  • NB LDDE recently found for opt/X-ray AGNs
  • Bongiorno et al. 07 Ueda et al. 03 Hasinger et
    al. 05
  • see also Vigotti et al. 03 Cirasuolo et al. 06
  • for radio AGNs

Connection between SFH MBH accretion
41
The Issue of Optical Identifications
Sub-mJy population very ELUSIVE!
Updated to 2003
Prandoni et al. 2004
INCOMPLETE OPT. ID. (tipically 50-60) More
severe for OPT. SPECTROSCOPY
42
The Issue of Optical Identifications
  • but in the last years, evolving picture
  • developement of photometric techniques
  • deep spectroscopy surveys
  • coordinated multi-? observational efforts
  • (e.g. PDS, VVDS, COSMOS, DPS, etc )

43
The ATESP-DEEP1 Sample
  • 5 GHz follow-up
  • 2x0.5 sq. deg. at d -40?
  • 2 radio mosaics with uniform rms flux ? 70 ?Jy
  • 111 sources with S gt 0.4 mJy
  • Spatial resolutions
  • ? 10 ? radio spectra
  • ? 2 ? radio morphology
  • 1.4 GHz ATESP Survey
  • 26x1 sq. deg. at d -40?
  • 16 radio mosaics with uniform rms flux ? 80 ?Jy
  • 2967 sources with S gt 0.4 mJy Spatial resolution
    ? 10

(Prandoni et al. 2000a,b 2001)
  • UBVRIJK imaging from DPS
  • 2x0.5 sq. deg. at d -40?
  • 4 WFI fields (DEEP1a,b,c,d) SOFI
  • UAB 25.7, BAB 25.5, VAB 25.2,
  • RAB 24.8, IAB 24.1
  • JAB 23.4 and 21.3 ltKs AB 22.7

(Prandoni et al. 2006)
DEEP 1
a
b
c
d
Mignano et al. 07a, Olsen et al 06
44
Assessing the Low-P AGN Component
  • Redshift Distribution
  • ETS up to z 2 (peak at z 0.5)
  • QSO ? 1.5ltz lt2.5
  • LTS ? zlt1
  • Radio Power Distribution
  • ETS ?1023-25 W Hz-1
  • (triggered by low-intermediate luminosity AGNs)
  • QSO ? P lt 1025-26 WHz-1
  • RI-QSOs
  • lower than usually found for classical radio-loud
    QSOs
  • LTS ? 2/3 P lt 1024 W Hz-1
  • (SF)

ATESP-DEEP1, Mignano et al. 2007b
67
12
16
? Sample largely dominated (78) by AGN activity
45
Assessing the Low-P AGN Component
5 GHz 111 ATESP RS
1.4 GHz 109 ATESP RS
NB double/ext RS
(Prandoni et al. 2006)
SIGNIFICANT FLATTENING WITH DECREASING FLUX S gt
4 mJy ? steep spectrum (amed -0.7, S ?a) S lt
4 mJy ? large fraction of flat spectra (a gt
-0.5)
significant of inverted spectra
(a gt0 )
46 at 1.4 GHz amed-0.53

63 at 5 GHz
amed-0.29
29 at 5 GHz
46
Assessing the Low-P AGN Component
Radio spectral index vs R - most a gt 0.5
sources ? high R Rgt1000 ? powerful RG and
QS0 - a gt 0.5 low R ? ETS RS probably
triggered by AGN - LTS/SB ? steep sources as
expected for synchrotron em. in gal. disks or in
nuclear SB
Mignano et al. 2007b
47
Assessing the Low-P AGN Component
Mignano et al. 2007b
Upper limits
Double/Extended RS
  • DEEP1abc
  • 39 ETS ? 24 with flat/inverted spectra
  • Typically compact (lt10-20 kpc)
  • P 5 GHz 1022-24 W Hz-1 ( ETS spectra) ?
    FRI class?

  • BUT
    FRI larger and steep

48
Assessing the Low-P AGN Component
  • compactness flat/inverted spectrum
  • ? Sinchrotron/free-free self-absorption
  • similar to so-called Low Power Compact (LPC) RS?
  • (P408 MHzlt1025.5 WHz-1, see Giroletti et
    al. 2005)
  • composite sub-class of FRI
  • Low-P BL Lac jet instability
    frustration
  • young sources? But GPS ? P 1.4 GHz gt 1025 W Hz-1
  • low accr./radiative efficiency (ADAF/ADIOS)
    LLAGN?
  • But typically P 5 GHz lt 1021 W Hz-1 (eg. Doi et
    al. 05)
  • unless ADAFjet ? higher P and still
    flat/inverted spectra
  • (eg. Falcke Biermann 99) ?
    further analysis needed

49
Assessing the Low-P AGN Component
? Multi-freq simultaneous obs. needed to confirm
spectra NB high freq. data (gt10 GHz) needed to
discriminate ADAF from more conventional
accretion schemes Jet-dominated sources -0.7lt a
lt 0.2 depending on relative contr. of extended
(opt-thin) and base (self-abs.) jet
components ADAF 0.2lt a lt 1.1 up to mm-? (Nagar
et al. 01) with a varying with accr. rate (a0.4
if L 10-4 LEdd a 1 if L 10-7 LEdd) NB
Coexistent outflows may flatten the spectra (but
agt0) Strong outflows may shift the peak
to cm ? (Quataert Narayan 99)
50
Comparison with Models
  • Models
  • RG QSO (Steep Flat)
  • Ev. SB normal Sp.
  • All
  • Datasets
  • ETSQSO LTS/SB All

General agreement between data and models At
Sgt0.4 mJy Ilt23.5 no evidence of a RQAGN
component Low-accr./radiative efficiency most
plausible scheme for flat-spectrum ETS
51
Modeling the Faint Radio Sky
ATCA VLA 6 x 22m
bsmax 6 km 27 x 25m bsmax 30 km
Westerbork 14 x 25 m bsmax 3 km
  • Typical resolution _at_ 1.4 GHz
  • 1-10 (to avoid confusion)
  • NB now close to telescopes detection limit (?1
    ?Jy _at_ 5 res.)

52
Modeling the Faint Radio Sky
  • Critical Issues
  • ev. of Low-P AGNs
  • extrapolation of local LF of SF AGN to lower
    powers

SKA EVLA VLA
53
Modeling the Faint Radio Sky
54
Modeling the Faint Radio Sky
  • NanoJy Radio Counts
  • A) AGN LF abruptly truncated at
  • P1.4 1020 W Hz-1
  • B) AGN LF does not flatten down to
  • P1.4 1018 W Hz-1

Slt100 nanoJy
55
Modeling the Faint Radio Sky
If hypothesis B) assumed SFGs ? largest
contribution at 0.1 lt S lt 100 ?Jy Non
ev. Sp. raise to 20 of the total at 10ltSlt100
nJy RG dominate at S lt 10 nJy !
RG
SB
QSO
Spirals
56
Modeling the Faint Radio Sky
Simulated Composition of the Faint Radio Source
Population as a function of flux Two redshift
ranges a) zlt1 b) zgt1 Models Radio Galaxies
AGNs (Sy1 Sy2) Non evolving Spirals
Starburst and post-SB
57
Implications for Future Deep Surveys
  • Large scale/all-sky deep surveys strongly needed
    to probe very faint end of the local LF ?
    constraints to the models
  • According to current observations and models
  • ? Ideal survey to study SFGs and their radio
    evolution (SFH a zgtgt 1) should have a limiting
    flux of 0.1 1 ?Jy
  • NB If spectral flattening related to nuclear
    activity ? low frequency selection (LOFAR) would
    clean the sample from AGN component
  • ? SKA may probe AGNs, high res. needed!

58
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