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Title: The nuclear activity of late-type galaxies in the Virgo Cluster


1
The nuclear activity of late-type galaxies in the
Virgo Cluster
Università degli Studi di Milano
Bicocca Dipartimento di Fisica
Università degli Studi dellInsubria Dipartimento
di Fisica e Matematica
  • Roberto Decarli

G. GavazziM. ColpiI. Arosio C. BonfantiL.
CorteseA. Boselli
Santiago, September, 6th, 2007
2
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3
The sample
  • The Virgo Cluster
  • is near us
  • is rich
  • is widely studied
  • We select all spiral galaxies in the Virgo
    Cluster Catalogue (Binggeli et al., 1985, 1993)
    with mph 15.
  • Among the complete sample of 237galaxies
  • 213 (90) have a spectroscopic classification
    fortheir nuclear activity
  • 216 (91) have NIR imaging
  • 199 (84) have r-band imaging

4
The AGN unified model
  • The SMBH influence radius is defined as the
    radius at which potential energies of the galaxy
    and of the massive BH are equal
  • The line emission near the SMBH is Doppler
    broadened because of the gas fast motion (gt1000
    km/s!) due to the SMBH potential well (Broad Line
    Region)
  • Lines produced outside Rinf are sensitive only of
    the galactic potential well (Narrow Line Region)

5
Line flux ratios and nuclear activity
  • Gas emission line fluxes depend on gas
    temperature, density, metallicity and on the
    intensity and energy distribution of the incident
    radiation field
  • Comparing line intensities one can infer
    information about the ionization source and its
    strength

VCC 664
Stasinska, 2006
AGNs
HII-regions
6
Spectroscopic datasets
  • Fluxes published in Ho, Filippenko Sargent
    (1997) 40 (40)
  • SDSS spectra 84 (73)
  • Nuclear spectra 29 (13)
  • Modified drift scan spectra 22 (4)
  • Drift scan spectra 193 (81)
  • Nuclear activity classification in NED 41 (2)

February-March, 2005-2006 observing runs in
Loiano GOLDMine database (http//goldmine.mib.i
nfn.it)
SDSS fiber
Slit
Nuclear spectra
Drift scan spectra
Modified drift scan spectra
7
NII /H? and OIII /H?
  • AGNs have NII/H? gt 0.6
  • OIII/H? gt 3 when a strong ionization field is
    present (Seyfert-like AGN or intensely
    star-forming region)
  • 0.4 lt NII /H? lt 0.6 for Transition objects
  • The NII/H? ratio provides a nuclear activity
    classification without any further information

8
56 AGNs (23.6)- 9 Seyfert (3.8)- 23
Seyfert/LINERs (9.7)- 24 LINERs (10.1) 21
Transition objects (8.9) 121 HII-Regions
(51.1) 15 No Emission Line Galaxies (6.3) 24 No
spectra available (10.1)
9
Dynamical mass andH-band luminosity
  • Mdyn dynamical mass up to the optical radius of
    the galaxy
  • Direct measures of Mdyn areobservational time
    consuming
  • For spiral galaxies
  • (Gavazzi et al., 1996)
  • We use H luminosity as a surrogate of Mdyn. NIR
    datawere taken from 2MASS and from GOLDMine
    databases

Adapted from Gavazzi et al. (1996)
10
Mass distribution
  • Only VCC 213 has Mdynlt1010 Mo and hosts an AGN
  • AGN fraction changes from 0 up to 100 when
    Mdyn changes between ?1010 Mo and ?31011 Mo
    (see also Kauffmann et al., 2003)
  • Mdyn gt 1010 Mo is a necessary condition for
    harbouring an AGN
  • Mdyn gt 31011 Mo is also a sufficient condition

11
The colour-magnitude diagram
  • The AGN host galaxies are usually found to be
    redder than non-active galaxies.
  • Some authors (e.g., Obric et al., 2006) suggested
    that the AGN feedback may be responsible of this
    effect.

AGNs populate the high-mass end of the same
colour-magnitude relation as the one observed for
inactive galaxies!
12
The role of bulges
  • From NIR light profile we define
  • Bulge dominated galaxies have C31gt4
  • Pure disks have C31?2.5
  • When Mdyngt 1011 Mo, both bulge- and
    disk-dominated spiral galaxies are found (see
    Gavazzi Pierini Boselli, 1996 Scodeggio et
    al., 2002)

Bulge-dominated spiral galaxies
AGNs are found in all the galaxies having
prominent bulges, but even in bulgeless galaxies!
Disk-dominated spiral galaxies
13
M100
M61
NGC4535
14
Light cusps
  • Sensitive to unresolved nuclei and light cusps
  • Nuc increases continuously with Mdyn

AGNs are found mainly at highvalues of Nuc
15
Are r-band nuclei the due to AGN continuum?
  • Nuclear spectra of 4 AGNs in our sample were
    observed with HST (Spinelli et al., 2006). All of
    them are well fitted with Bruzual Charlot
    libraries of star spectra.
  • AGN continuum light is thus negligible with
    respect to the stellar component.

VCC 1110 - Seyfert
VCC 2070 - LINER
VCC 1401 - Seyfert
VCC 1690 - LINER
16
Environment I
  • We divide our sample in two parts, according to
    the angular separation of the galaxies from M87
  • High density subsample 114 galaxies, 37 AGNs
    (328 )
  • Low density subsample 99 galaxies, 40 AGNs
    (4010 )
  • The mass distribution of the subsamples are
    similar.
  • The observed AGN fractions are consistent.

17
Environment II
  • We check the NII/Ha dependence on the neutral
    gas deficiency (Haynes Giovanelli, 1984).
  • Even considering the HI deficiency no clear
    environmental effect is observed, once the
    luminosity dependence is taken into account.

The environment does not significantly influence
thenuclear activity
18
What can we argue about the BH-host galaxy joint
evolution?
  • At least in spiral galaxies, the nuclear activity
    is strongly sensitive to the host galaxy mass,
    while the morphology plays a secondary role.
  • The environment is not relevant in nuclear
    activity.
  • There is no evidence of a strong feedback
    mechanism in the galaxy colours.
  • Low accretion rates are observed.

19
  • The massive BH may have grown simultaneously with
    the galaxy, in an anti-hierarchical way
  • The dynamical mass is the driver of both the
    galaxy and the BH growth, in a top-down scenario
  • The scale relations inset during the formation
    itself of the system
  • Galaxies do not require any strong feedback later
    on, neither strong accretion rates
  • The fragile morphology of pure disk and
    bulgeless galaxies is preserved, since the BH is
    already formed

20
Bibliography
  • Decarli, Gavazzi, Arosio, Cortese, Boselli,
    Bonfanti, Colpi, 2007, arXiv0707.0999, accepted
    for publication in MNRAS
  • Ferrarese, 2006, in Series in High Energy
    Physics, Cosmology and Gravitation, Joint
    Evolution of Black Holes and Galaxies', ed. by M.
    Colpi, V. Gorini, F. Haardt, U. Moschella (New
    York - London Taylor Francis Group), 1
  • Gavazzi, Pierini Boselli, 1996, AA, 312, 397
  • Gavazzi, Boselli, Scodeggio, Pierini Belsole,
    1999, MNRAS, 304, 595
  • Gavazzi, Boselli, Donati, Franzetti Scodeggio,
    2003, AA, 400, 451
  • Haynes Giovanelli, 1984, AJ, 89, 6
  • Kauffmann et al., 2003, MNRAS, 346, 1055
  • Kauffmann Heckman, 2005, RSPTA, 363, 621
  • Lequeux et al., 1979, AA, 80, 155
  • Marconi Hunt, 2003, ApJ, 589, L21
  • Obric, et al., 2006, MNRAS, 370, 1677
  • Scodeggio, Gavazzi, Franzetti, Boselli, Zibetti,
    Pierini, 2002, AA, 384, 812
  • Veilleux, et al., 2003, AJ, 126, 2185

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22
Correcting for line absorptions
  • Balmer lines are usually observed both in
    emission and in absorption
  • When possible, both the emission and absorption
    features are fitted. Otherwise, a correction is
    applied assuming various templates according to
    the galaxy luminosity.

23
Spectroscopic datasets
  • Fluxes published in Ho, Filippenko Sargent
    (1997) 40 (40)
  • SDSS spectra 84 (73)
  • Nuclear spectra 29 (13)
  • Modified drift scan spectra 22 (4)
  • Drift scan spectra 193 (81)
  • Nuclear activity classification in NED 41 (2)

February-March, 2005-2006 observing runs in
Loiano GOLDMine database (http//goldmine.mib.i
nfn.it)
Slit
Drift scan spectra
Nuclear spectra
Modified drift scan spectra
SDSS fiber
24
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25
The NII/Ha ratio along the slit
26
The Narrow Line Region size
  • For a subsample of AGNs, we extract the NII/Ha
    ratio at various apertures, up to some kpc
  • Only in one galaxy (VCC 73) the ratio
    significantly descreases in the first kpc

Veilleux et al., 2003
  • Thus, the photoionization of an AGN extends up
    some kpc!

27
Mass dependence
  • The NII/H? ratio increases with the dynamical
    mass of the host galaxy
  • A bimodality is observed
  • In low-mass host galaxies, the NII/H? ratio is
    a metallicity indicator
  • At higher masses, a further contribution to the
    NII/Ha ratio is provided by the AGN

28
Black hole masses
  • Only few tens direct supermassive BH mass
    measures are available, mostly in elliptical
    galaxies (see Ferrarese, 2006 for a review)
  • Following Marconi Hunt (2003), the MBH of our
    sample AGNs is estimated from the bulge NIR
    luminosity
  • All the BHs in our sample have MBHgt105.8 Mo.

29
The accretrion rate L/LEdd
  • The accretion rate is usually identified with the
    ratio between the AGN bolometric luminosity and
    the BH Eddington luminosity

Most of our objects have very low accretion rates
  • The AGN bolometric luminosity is roughly
    proportional to the OIII luminosity (Heckman et
    al., 2004).
  • We thus have an order-of-magnitude estimate of
    L/LEdd for our objects.

30
Summarizing
  • Mdyngt1010 Mo is a necessary condition to harbour
    an AGN
  • The AGN fraction steeply rises with the dynamical
    mass, and it is virtually 1 when Mdyngt31011 Mo
  • AGNs are found even in a number of bulgeless
    galaxies
  • Nuclear stellar cusps are often found in AGN host
    galaxies
  • The same colour-magnitude relation describes both
    active and inactive galaxies
  • No significant environmental dependence of the
    nuclear activity is observed
  • All the AGNs in our sample have MBHgt105.8 Mo
  • Very low accretion rates are found in almost all
    our targets
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