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ACTIVE GALACTIC NUCLEI Optical spectral classification and Luminosity Function Introduction and some caveats Sy1/QSO QSO/quasar NLRG/QSO2/Sy2 RL QSO/RQ QSO Point-like/extended

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active galactic nuclei

ACTIVE GALACTIC NUCLEI

Optical spectral classification and Luminosity Function

introduction and some caveats
Introduction and some caveats
  • Sy1/QSO
  • QSO/quasar
  • NLRG/QSO2/Sy2
  • RL QSO/RQ QSO
  • Point-like/extended

”Active galactic nuclei (AGN) are a class of galaxies where a significant fraction of the energy output, emerging from their centers, is not produced by the normal galaxy components : stars, dust and interstellar gas. This energy can be emitted across the whole electromagnetic spectrum, from radio waves to gamma rays”

Reducing the AGN zoo

as much as possible !

Marco Mignoli: AGN Optical Classification & Luminosity Function

the uv optical nir spectrum
The UV/optical/NIR spectrum
  • Power-law: emitted by an highly compact non-thermal source (power law)
  • Big Blue Bump: this component possibly comes from the BH accretion disk (black body)

Marco Mignoli: AGN Optical Classification & Luminosity Function

the uv optical agn spectrum
The UV/optical AGN spectrum
  • Power-law
  • Big Blue Bump
  • Small Blue Bump: FeII+Balmer Continuum
  • Broad emission lines: FWHM > 1500 Km/s
  • Narrow emission lines: FWHM < 900 Km/s

The emission lines characterize the AGN spectra: they are produced in two separate regions, a subarcsec Broad Line Region (BLR) close to the central engine, and a more extended Narrow Line Region (NLR).

  • Galaxy Starlight: usually overwhelmed by the AGN non-thermal continuum and emerging in the red part of the spectrum

Marco Mignoli: AGN Optical Classification & Luminosity Function

the uv optical emission line spectrum
The UV/optical emission line spectrum

Marco Mignoli: AGN Optical Classification & Luminosity Function

what we learn from the agn uv optical spectra
What we learn from theAGN UV/optical spectra
  • Redshift
  • Classification (optical): Type 1/Type 2
  • AGN Unification: evidences
  • Physical state of the emitting-line gas
  • AGN/StB separation: Diagnostic Diagrams
  • Unconventional AGNs

Marco Mignoli: AGN Optical Classification & Luminosity Function

redshift
Redshift
  • Discovery of the true nature of quasar
  • Cosmological Distance
  • Absolute physical quantities (L,M,size)
  • Only the optical spectrum (sometimes UV, near-IR) gives z
  • Easy way to measure z

Marco Mignoli: AGN Optical Classification & Luminosity Function

in 1963 schmidt identifies highly redshifted balmer lines in 3c273 s spectrum
In 1963 Schmidt identifies highly redshifted Balmer lines in 3C273’s spectrum

z = 0.158 (vr = 47500 km/s)

Marco Mignoli: AGN Optical Classification & Luminosity Function

redshift9
Redshift
  • Discovery of the true nature of quasar
  • Cosmological Distance
  • Absolute physical quantities (L,M,size)
  • Only the optical spectrum (sometimes UV, near-IR) gives z
  • Easy way to measure z

Marco Mignoli: AGN Optical Classification & Luminosity Function

agn emission line spectra
AGN emission line spectra
  • Type 1 AGNare those with very broad optical/UV permitted emission lines, with FWHM~1500-15000 km/s, while the forbidden lines, like [OII]3727, [OIII]4959/5007, [NII]6548/6583, typically have FWHMs of order of 500-1000 km/s.
  • Type 2 AGN have permitted and forbidden lines with approximately the same FWHM, similar to the FWHMs of the forbidden lines in Type 1 objects.

The forbidden lines, while narrower than the permitted ones, are usually broader than the emission lines in most starburst galaxies.

Optical Type 1

Optical Type 2

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide11

AGN Unification: the “standard model”

Components:

Accretion Disk: r ~ 10−3pcn ~ 1015cm−3v~ 0.3c

Broad Line Region: r ~ 0.01−0.1 pcn ~ 1010cm−3v ~ few x 103km s−1

Dusty Torus: r ~ 1−100 pcn ~ 103 −106 cm−3

Narrow Line Region: r ~ 100−1000 pcn ~ 102 −104cm−3v ~ few x 102km s−1

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide12

AGN Unification: the paradigm

“... Much of the variety in AGN types isjust the result of varying orientation relative to the line of sight. [...]

We can define an extreme hypothesis in which there are only two basic AGN types: the radio quiet and radio loud.”

(Antonucci 1993)

XBONG

Marco Mignoli: AGN Optical Classification & Luminosity Function

spectral classification em lines
Spectral classification (em.lines)
  • Type 1
  • Type 2
  • Starforming galaxies

Marco Mignoli: AGN Optical Classification & Luminosity Function

spectral classification em lines14
Spectral classification (em.lines)
  • Type 1
  • Type 2
  • Starforming galaxies

How we can discriminate the narrow line objects?

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide15

Spectral classification (em.lines)

SDSS

DIAGNOSTIC DIAGRAM

  • Sy 1 galaxies
  • Sy 2 galaxies
  • Starforming galaxies
  • Composite galaxies

Marco Mignoli: AGN Optical Classification & Luminosity Function

diagnostic diagrams
Diagnostic Diagrams

SDSS

  • Sy2/StB theoretical separation Kewley et al. (1991)

Marco Mignoli: AGN Optical Classification & Luminosity Function

diagnostic diagrams17
Diagnostic Diagrams

SDSS

  • Sy2/StB empirical separation Kauffmann et al. (1994).

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide18

Diagnostic Diagrams

The BPT diagrams (Balwin, Phillips & Terlevich 1981, Veilleux & Ostrebrock 1987),are usedin narrow-line emission systems, to distinguish between the origins of the photo-ionization, hard and soft radiation, which is usually ascribed to non-stellar and stellar activity, respectively.

The general criterium [O III] / Hβ > 3 could be wrong !

Shock-heated

Power-law

Sey2

Planetary nebulae

LINERs

H II gal

H II galaxies

(BPT 1981)(Peterson 1997)

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide19

Diagnostic Diagrams

DIAGNOSTIC DIAGRAMS

Em.lines in the red range

  • [NIII]6584/Hα vs. [OIII]5007/Hβ
  • [SII]6717-31/Hα vs. [OIII]5007/Hβ
  • [OI]6300/Hα vs. [OIII]5007/Hβ

Em.lines in the blue range

  • [OII]3727/Hβ vs. [OIII]5007/Hβ
  • [OII]3727/Hβ vs. continuum index

Other line ratios in UV, NIR andFIR spectral ranges

NV1240/Lyα, NV1240/HeII1640, CIV /Lyα

[Si VI] 1.962μm/Paα

[NeV]14μm/[NeII]12.8μm,

[OIV]26μm/[NeII]12.8μm,

EW(PAH 7.7μm)

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide20

AGN taxonomy: LINERs

LINER= Low-Ionization Narrow-Line Region

They are characterized by [O II] λ3727Å / [O III] λ5007Å ≥ 1

[O I] λ6300Å / [O III] λ5007Å ≥ 1/3

Most of the nuclei of nearby galaxies are LINERs. A census of the brightest 250 galaxies in the nearby Universe shows that 50–75% of giant galaxies have some weak LINER activity(Phillips et al. 1986, Ho, Filippenko & Sargent 1993, …).

They are the weakest form of activity in the AGN zoo.

(Heckman 1980)

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide21

AGN taxonomy: BAL QSOs

BAL QSOs= Broad Absorption Line QSOs

Otherwise normal QSOs that show deep broad absorption lines, blueward of the corresponding emission resonance lines of CIV, SiIV, NV. The interpre-tation is that they are intrinsic and arise from clouds outflowing the nucleus.

They mainly are at z ≥ 1.5 because the phenomenon is observed in the rest-frame UV. At these redshifts, they are ~10% of the observed population.

Mean QSO spectrum PG 0946+301. Arav et al. (1999)

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide22

AGN taxonomy: BL Lacs & Blazars

  • BL Lacertaeis the prototype of this class: an object, stellar in appearance, with very weak emission lines and variable, intense and highly polarized continuum. The weak lines often just appear in the most quiescent stages. BL Lacs, along with optically violent-variable (OVV) QSOs, constitute the class of Blazars: these are believed to be objects with a strong relativistically beamed jet in the line of sight.

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide23

AGN taxonomy: XBONGs

XBONGs= X-rayBrightOpticallyNormalGalaxies

This AGN class consists of luminous hard X-ray sources hosted by "normal" galaxies with optical spectra typical of early-type systems (Comastri et al. 2002). Why the relatively bright X-ray emission, typical of moderately luminous (1042-43 erg s-1) Active Galactic Nuclei , does not leave any optical signature of the presence of a nuclear source is still matter of debate.

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide24

AGN taxonomy: XBONGs

  • The upper limits on the optical emission lines ([OIII], Hα), expected from the nuclear activity, in some XBONGs are tight enough to place these sources outside the typical AGN properties.
  • Possible interpretations:
  • Dilution from the host galaxy light
  • Radiatively inefficient accretion flow
  • Heavy obscuration by Compton-thick nuclear gas
  • NLR obscured on galaxy scale (i.e., Kpc dust lanes, see Malkan et al. 1998, Rigby et al. 2006)
  • Extreme BL Lacs objects

Hellas2XMM

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide25

AGN taxonomy: the type-2 QSOs

Definition:

“Quasar (high L) analogue of Sy2 galaxies”

OPTICAL:high bolometric luminosity (→ high z) objects with high ionization, narrow (FWHM<1500km/s) emission lines, no broad lines. (expected according to the Unification models of AGN)

X-RAYS: high-luminosity (Lx> 1044 erg/cm/s2) and obscured (NH>1022cm-2) AGN (required by XRB synthesis models).

Do obscured (type II) quasars exist? To date, only a small number of candidates have been found (but NLRG). First examples did not confirm their classification after follow-up observations (high S/N and/or redward).

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide26

AGN taxonomy: the type-2 QSOs

Boyle et al. (1999)

Type2

Without the low order Balmer lines, a secure type2 classification is a moot point.

Halpern et al. (1999)

Type 1

Marco Mignoli: AGN Optical Classification & Luminosity Function

agn taxonomy the type 2 qsos
AGN taxonomy: the type-2 QSOs

The high-z type-2 QSOs do exist! Selected both in optical, X-rays and FIR. But they are demanding targets for optical spectroscopy. (but see SDSS…)

Stern et al. (2002)

Norman et al. (2002)

Martinez-Sansigre et al. (2005)

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide28

The “redshift desert” for type-2 QSOs

Redhift desert (1.4<z<2)

High-z range

Low-z range

Marco Mignoli: AGN Optical Classification & Luminosity Function

optical spectra of different agn types
Optical spectra of different AGN types

Marco Mignoli: AGN Optical Classification & Luminosity Function

points to take away 1
Points to Take Away (1)
  • The optical spectrum offers a wealth of information about BLR/NLR and the AGN structure, but it is mainly composed by “secondary” radiations.
  • The unification scheme is a clear and simple way to classify AGN, but don’t tell us all the truth.

ty1/ty2 ↔ f(L),f(z),f(λ),f(env),f(host-type),f(t)

  • Multi-wavelength approach to AGN study

Marco Mignoli: AGN Optical Classification & Luminosity Function

the luminosity function
The Luminosity Function
  • To study galaxy/AGN evolution we need to compare extragalactic objects today with the same kind of objects in the past
  • To perform a fair comparison we need to compare the emitted power at the same wavelengths, hence K-corrections [k(z)]
  • We cannot observe the same galaxy at different times, so we must look at the statistical properties as populations, hence we study Luminosity Functions (LF)

Marco Mignoli: AGN Optical Classification & Luminosity Function

the luminosity function33
The Luminosity Function
  • The luminosity function characterises the number density of (active) galaxies as a function of the luminosity L
  • Luminosity function, usually written (L), is defined as the co-moving number density (number of objects per co-moving volume) in some luminosity range (usually logarithmic)

Marco Mignoli: AGN Optical Classification & Luminosity Function

the luminosity function34
The Luminosity Function
  • In order to allow easy comparison between different determinations and different types of LF it is usual to use simple parameterisations
  • Schecter  common for galaxies
  • Two-Power-Law  common for AGN
  • Power-Law with exponential cut-off  infrared galaxies

Marco Mignoli: AGN Optical Classification & Luminosity Function

lf schecter function for galaxies

Power-Law slope a

*

Log((L))

L*

Log (Luminosity)

LF: Schecter Function (for galaxies)

Exponential Cut-off

Marco Mignoli: AGN Optical Classification & Luminosity Function

parametric evolution of luminosity functions

*

Log((L))

L*

Log (Luminosity)

Parametric Evolution of Luminosity Functions

Pure density evolution

Density

Evolution

Pure Luminosity evolution

Luminosity

Evolution

Marco Mignoli: AGN Optical Classification & Luminosity Function

parametric evolution of luminosity functions37

Density

Evolution

*

Log((L))

Luminosity

Evolution

L*

Log (Luminosity)

Parametric Evolution of Luminosity Functions

Marco Mignoli: AGN Optical Classification & Luminosity Function

luminosity function methods of calculation
Luminosity Function: methods of calculation

LF is just the number density of galaxies…

… so just have to count the number of galaxies...

… and divide by the observable volume of each one.

… simple but ....

Only complication is the magnitude limits of the survey

  • 1/Vmax (move the galaxy)

Move the galaxy forwards and backwards in redshift, to find the maximum volume it could have inhabited and still been observed.

  • Maximum likelihood (change its brightness)

At a fixed redshift, what is the range of luminosities that a galaxy could have - and still be observed… need to assume a form for the LF.

Marco Mignoli: AGN Optical Classification & Luminosity Function

the qso lf goals
The QSO LF: goals
  • The optical luminosity functions of quasars (OLF), as well as different types of AGN, hold important clues about the demographics of the AGN population, providing strong constraints on physical models and evolutionary theories of AGN.
  • The QSO OLF at high redshifts provides important constraints on the ionizing UV radiation field of the early universe.
    • The faint end of the QSO LF has not been measured at high redshift until now. Instead, low-z measurements of the faint end were combined with high-z measurements of the bright end to estimate the entire LF at high z.
  • The luminosity function of quasars is one of the principal constraints on the accretion history of the most massive black holes

Marco Mignoli: AGN Optical Classification & Luminosity Function

the qso lf goals40
The QSO LF: goals
  • Derive the density of AGNs as function of bolometric luminosity, redshift

(Lbol | z |type)

  • Relates to:
    • Characterizing accretion history:
      • Distribution functions of black hole activity as function of MBH, accrection rate and radiative efficiency and redshift
    • Probing galaxy/BH coevolution
    • Test unification model

Marco Mignoli: AGN Optical Classification & Luminosity Function

the qso lf basic issues
The QSO LF: basic issues

Instead of (Lbol| z | type), we observe:

  • N(f, z, AGN type, selection criteria)
  • Selection effect
    • Incompleteness due to selection criteria (correctable)
    • Selection bias (e.g., optical survey missing obscured sources)
  • Bolometric correction
  • Redshift effect
    • Flux-limited vs. volume limited, truncated data set
    • Limited luminosity range at any given redshift
    • K-correction

Marco Mignoli: AGN Optical Classification & Luminosity Function

accretion history of agns
Accretion history of AGNs

Quasar space density as a function of redshift.

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide43

Luminosity function describes the space number density of AGNs with luminosity L at redshift z.

The black hole mass density accreted in bright AGN phases is

where is the AGN luminosity function,

is radiation efficiency.

Accretion history and luminosity function of AGNs

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide44

The local black hole mass density can be estimated from the optical data by using relation (Yu & Tremaine 2002, Marconi et al. 2004):

Black hole mass density and the OLF of AGNs

Local black hole mass density mainly comes from the accretion during bright AGN phases.

Marco Mignoli: AGN Optical Classification & Luminosity Function

formation history of the smbhs mass density
Formation history of the SMBHs: mass density
  • Total accreted mass (hence BH mass density) can be estimated by LF assuming the mass-to-energy conversion factorε(Soltan 1982).
  • Compare with a local BH mass density estimated from the relation between BH mass and velocity dispersion to constrain ε.
  • Previous studies:
    • Fabian and Iwasawa (1999) , Elvis et al (2002):

use the XRB intensity assuming z=2 for all the XRB source

    • Yu and Tremaine (2002)

use the QSO optical LF from 2dF survey

    • Marconi et al. (2004)

use both the XRB and SDDS data (galaxies & quasars)

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide46

1. Birth of AGNs

Major mergers between galaxies trigger nuclear gas flows to feed the BH, and trigger nuclear starbursts. The nucleus is obscured by dense gas.

2. Bright AGN phase

Accreting at around or slightly less than the Eddington rate. The gas

becomes transparent and the nucleus can be seen.

3. Death of bright AGNs

Radiation of AGNs expels gases to quench both BH accretion and star formation.

4. Faint AGN phases

Accreting at very low rates

The scenario for AGN formation and evolution

Marco Mignoli: AGN Optical Classification & Luminosity Function

the qso lf parameterization
The QSO LF: Parameterization
  • Quasar LF: double power-law
  • Luminosity-dependent density evolution (Schmidt and Green 1983):

(L,z) = (L,z) (L,z=0)

Overall density evolves;

Shape (bright and faint end slopes) evolves as well

Marco Mignoli: AGN Optical Classification & Luminosity Function

qso luminosity function from 2df quasar survey

2QZ

QSO Luminosity Function from 2dF Quasar Survey

www.2dfquasar.org

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide49

3 Lya

2 CIV

CIII

MgII

1

OIII

0 4000 Åobserved wavelength8000 Å

redshift

properties of the 2df quasar survey
Properties of the 2dF Quasar Survey
  • Quasars selected from pointlike sources using U-B:B-R colours (UVX)
  • 0.3<z<2.5
  • ~25000 B<21 QSOs in final catalogue
  • Volume probed ~4 x109h-3Mpc3

www.2dfquasar.org

Croom et al. 2002, MNRAS, 322, L29

Croom et al. 2004, MNRAS, 349, 1397

Marco Mignoli: AGN Optical Classification & Luminosity Function

optical counts from 2df quasar survey
Optical Counts from 2dF Quasar Survey

Marco Mignoli: AGN Optical Classification & Luminosity Function

optical luminosity function from 2df quasar survey
Optical Luminosity Function from 2dF Quasar Survey

Boyle et al. 2001

Marco Mignoli: AGN Optical Classification & Luminosity Function

optical luminosity function from 2df quasar survey53
Optical Luminosity Function from 2dF Quasar Survey

Best fit model: pure luminosity evolution (PLE):

 = cosmic look-back time;  ~ 6;  ~ -3.3;  ~ -1.0

  • M* constant apparent mag - Selection effect??
  • Faint end slope poorly determined

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide54

PLE

PDE

Marco Mignoli: AGN Optical Classification & Luminosity Function

sdss quasar survey
SDSS Quasar Survey

QSOs selected from imaging in 5 wavebands – u g r i z

Multi-colour selection  Sensitive to QSOs at high redshift (z<6.5)

Currently ~50000 QSOs in DR3

i<19 (main sample) i<20 (high-z sample)

NGP SGP

Schneider et al. 2003, AJ, 126, 2579

www.sdss.org

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide56

46,420 Quasars from the SDSS Data Release Three

5

Ly forest

3

Ly

2

CIV

redshift

CIII

MgII

FeII

1

FeII

H

OIII

0

Marco Mignoli: AGN Optical Classification & Luminosity Function

wavelength

4000 A

9000 A

hubble diagram for sdss
Hubble diagram for SDSS

Marco Mignoli: AGN Optical Classification & Luminosity Function

sdss quasar olf

Richards et al. 2006

SDSS quasar OLF

Marco Mignoli: AGN Optical Classification & Luminosity Function

sdss quasar olf evolution at high redshift

< 2QZ range >

SDSS quasar OLF: evolution at high redshift ?
  • The SDSS counts and LF agree with the results of the 2QZ at redshifts and luminosities at which the two samples overlap, but the SDSS data probe to much higher redshifts than does the 2QZ sample.
  • Strong evolution in bright end slope at z>3 (can’t be PLE all the way); the slope flattens with redshift.
  • But SDSS doesn’t go faint enough at low-z to differentiate PLE from PDE or else.....

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide60

COMBO-17

Due to the relatively bright magnitude limits of the SDSS and 2QZ surveys, the LF analysis is restricted to relatively bright QSOs – especially at high redshift.

What about fainter QSOs?

The COMBO-17 survey, using multi-band photometry in 17 filters within 350 nm < obs < 930 nm, simultaneously determine photometric redshifts with an accuracy of Δz < 0,03 and obtain spectral energy distributions.

Photometric selection of 192 1.2<z<4.8 QSOs, reaching R~24

Marco Mignoli: AGN Optical Classification & Luminosity Function

Wolf et al. (2003)

combo 17 olf at z 1
COMBO-17: OLF at z>1

The evolving LF can be adequately described by either PLE (red dashed line) or PDE (black solid line) – largely due to the absence of an obvious break.

Marco Mignoli: AGN Optical Classification & Luminosity Function

faint end of the quasar lf fainter qso surveys
SDSS photometry & 2dF spectroscopy

1m deeper than 2QZ

Multicolor selection

5645 qso in 100+deg2

2SLAQ counts and LF are steeper in the faint end (34% more faint quasars)

LF: PLE evolution of a double power-law but no well-defined break (PDE not rejected)

Broad Line objects in the pure magnitude selected VVDS

130 AGN down to I = 24

Bongiorno et al. (2007) merge VVDS & SDSS samples to find Luminosity Dependent Density Evolution (LDDE ) model for the OLF of broad line AGN.

The peak of AGN space density shifts to lower redshifts for the lower luminosity objects (AGN cosmic downsizing) see X-rays !!

Faint end of the quasar LF  fainter qso surveys

2dF-SDSS QSO survey (2SLAQ)

VVDS type-1 AGN sample

Marco Mignoli: AGN Optical Classification & Luminosity Function

unaccounted agns
Unaccounted AGNs
  • Significant obscured population:

e.g. Seyfert 2s, Narrow line radio galaxies. How many type 2 QSOs?

  • Low luminosity AGNs

e.g. Seyfert 1s, LINERs.

host dilution, lack of all emission lines for diagnostic tests (z > 0.5)

Cosmic X-ray Background

NH ~ 1020 cm-2NH ~ 1024 cm-2

Gilli, Comastri & Hasinger 2006

Do they contribute significantly to the cumulative emissivity of AGNs?

Yu and Tremaine (2002) match local BH mass density using the OLF of QSOs.

Marco Mignoli: AGN Optical Classification & Luminosity Function

agn x ray lf motivation
AGN X-ray LF: motivation
  • X-rays AGN Luminosity Function:

a goal of X-ray surveys

the most fundamental measure to understand the cosmological evolution of AGNs

  • How many AGNs in the universe (as a function of time)?
  • How supermassive black holes form?

see Roberto Gilli Lesson

Marco Mignoli: AGN Optical Classification & Luminosity Function

slide65

AGN X-ray LF

  • Quasar density peaks at z~2-3
  • Low-L AGN density peaks at z~0.5 - 1
  • Paradox 1:
    • Most of BH accretion happens in quasars at high-z
    • Most of X-ray background in Seyfert 2s at low-z

Marco Mignoli: AGN Optical Classification & Luminosity Function

agn x ray lf
AGN X-ray LF

PLE doesn’t work; need luminosity-dependent density evolution (LDDE) to characterize evolution of the XLF

Miyaji et al. 2006

Marco Mignoli: AGN Optical Classification & Luminosity Function

agn x ray lf67
AGN X-ray LF
  • Type 2 fraction a strong function of luminosity
  • Paradox 2:
  • At high (quasar) luminosity: type 2 <20%; optical color selection is highly complete since almost all are type 1s, and includes most of luminosity AGN population emitted in the Universe.
  • At low (Seyfert) luminosity: type 2 ~80%; optical color selection miss most of the AGNs in the Universe in terms of number .
what do the optical surveys tell us about quasar lf
What do the optical surveys tell us about quasar LF ?
  • The LF is a powerful tool for the study of AGN population (demography and structure)
  • LF determination: bright end/high-z needs large survey area (rare objects) – faint end /high-z needs deep surveys (faint objects). Requisite to populate the bins  large N surveys. NO single survey
  • Survey ε= f (band| z |AGN type |selection criteria )  Multiwavelength approach to AGN study (again)
  • For some applications (e.g. BH mass density) the OLF of bright quasar is adequate.

Marco Mignoli: AGN Optical Classification & Luminosity Function