This preview shows page 1. Sign up to view the full content.
Unformatted text preview: 1/15/12 Gala ie and he Uni e e - Ho H
S G Gala ie of Ac i e N clei A AGN N ,
. Se fe rt gala ie s ,
90, 241; A
1977 A JS AGN S
1980 A J 237, 404; H
33, 19). C
. 83). O
S ,S ,
(Y 1983 A J 272, 483). H
1992 A JS
, 79, 49),
1984 A&A 136, 206). A
1989 A JL 342, L11). T
. Radio gala ie s ,
M , ,
( , (M
- ,M '
1964 A J 140, 35) 1980 PASP ,
1978 A J 224,
1985 A J 228, 122),
1981 A J 245, 25; S
1978 AJ 83, 348; A
1980 AJ 85, 1010; Z
1997 A J
476, 489). T
1986 A J 311, 526; S
1989 A J 341, 658; 1990
A J 348, 38; S
1990 A J 356, 399). W
3C 305 (
1984 A J 287, 82;
1982 A J 262, 529). FR I
(D .a . a.ed /keel/gala ie /agnho .h ml 1/4 1/15/12 Gala ie and he Uni e e - Ho Gala ie of Ac i e N clei A '.T
I ( ) - 0313- 192
3C 305. N 3C 293
.R A , 428. T
S , ISM .J , - A ( ISM S , . ,
- , ; .A alignme n e ffe c AGN > 0.5. I
MC 3C 368),
. 1987 (A JL 319, L39) Qaa
.a . a.ed /keel/gala ie /agnho Q SO
.h ml ,
- - , P .F
(1993 MNRAS 263, 936).
, , ' .F
(K 1973 A JL
2/4 1/15/12 Gala ie and he Uni e e - Ho Gala ie of Ac i e N clei 179, L129; Gehren et al 1984 ApJ 278, 11; Hutchings et al 1984 ApJSuppl 55, 319; Malkan 1984 ApJ 287, 555). Such fuzz
is detectable for most QSOs at < 0.4 by now. Spectroscopic confirmation that these are galaxies containing (more or less)
normal stars has been difficult, because the fuzz is of low surface brightness and close to a strong point source. First attempts
found extended emission lines (Wampler et al 1975 ApJ 198,249, Richstone and Oke 1977 ApJ 213, 6; Stockton 1976
ApJLett 205, 115...) Stellar absorption features (from a fairly young population) were clearly found around 3C 48 by Boroson
and Oke (1982 Nature 296, 391). Several more cases have now been observed, all at the QSO redshift (Boroson and Oke
1984 ApK 281, 535; Boroson and Green 1982 ApJ 263, 32; Balick and Heckman 1983 ApJLett 265, L1; Boroson et al.
1985 ApJ 293, 120). Boroson et al. suggest that there are two kinds of QSO host galaxies: those with young stellar
populations (often radio- loud) and redder fuzz with emission lines lit up by the QSO (radio- quiet). This contravenes the
conventional wisdom that radio- loud objects live in normal ellipticals. A QSO could have significant impact on the surrounding
galaxy, so maybe the conventional wisdom expected too much.
HST imaging has, as long expected, produced spectacular results on quasar host galaxies, even if not the results that many
people expected. QSOs can live in normal spirals or ellipticals, and in many cases in quite faint or small (compact) galaxies.
Many show spectacular tidal distortions, and most have close compact companions. The references are given back in the
interaction and merger lecture. It is still striking that there is not a very good correlation between the core power and galaxy
luminosity. There is a limit or envelope in that the brightest AGN come in unusually luminous galaxies, and the probability of
hosting an AGN increases for brighter galaxies.
Note that there is an overlap in luminosity between luminous Seyferts and QSOs depending on who is writing - at < 0.2 it's
not clear one is dealing with traditional QSOs in many cases. However, there is no doubt that the fuzz around 3C 48 and 3C
273 represents galaxies around bona f ide QSOs. Some lower- luminosity objects discussed in this context (Malkan et al 1984
ApJ 280, 66; Bothun et al 1982 ApJ 257, 46) are distant Seyferts and not really suitable as "proof" that QSOs are in some
kind of galaxy or other. A supernova has been reported in the galaxy around 1059+730 at =0.039 by Campbell et al 1985
(ApJLett 291, L37). Some resolved structure has been reported around QSOs at < 2, which cannot be nornal galaxies
because the cosmological (1+ )4 surface- brightness dimming (or Tolman dimming) would drop their diffuse flux beyond
detection. In the local Universe, such objects as PG 1351+640 have such low limits on host- galaxy lyuminosity or
compactness as to require that the host galaxy is no larger or brighter than M32. In the other direction, there are signs that
some high- redshift QSOs must live in extremely luminous "superhosts". This may be attributable to a starburst- AGN
connection, if the timescales are right.
There have been numerous reports of clusters of galaxies around QSOs (Phillips 1980 ApJLett 236, L45; Kriss and Canizares
1982 ApJ 261, 51; Hintzen et al 1981 ApJLett 246, 21; French and Gunn 1983 ApJ 269, 29; Yee and Green 1984 ApJ 280,
79 and ApJSuppl 54, 495). The Yee and Green survey produced evidence that the fraction of QSOs in rich clusters has
dropped steeply between =0.5 and now.
Even using HST, detailed work on QSO host galaxies is extremely difficult - - some objects have surface- brightness profiles
consistent with normal E or S galaxies but this is not unique because one is limited to the outer region (by the wings of the bright
nuclear image and uncertainties in its radial profile) and thus to regions of low surface brightness. Are the host galaxies of
luminous AGN always disturbed? How much alteration has been produced by star formation either contemporary with or
triggered by the AGN?
Evidence of a relation between black- hole mass and bulge properties (sometimes known as the Magorrian relation) has
focussed attention on the co- evolution of nuclei and bulges. Correlations exist with bulge absolute magnitude (often expressed
as stellar mass, in the half- percent rule) and velocity dispersion:
M = 1.48 ± 0.24 x 108 ( /200 km/s) 4.65 ± 0.48
following papers by Ferrarese and Merritt and Gebhardt et al. (both 2000). A relation of this kind likely means that the bulge
initially regulates the formation of a massive black hole, which grows until its dynamical influence reshapes stellar orbits in its
vicinity. It is not ruled out that the black holes came first, but the tightness of the correlation (± 50% or so) is suspiciously good
for this. The return of STIS promises to give us more points testing this relation in different and more extreme environments,
.a . a.ed /keel/gala ie /agnho .h ml 3/4 1/15/12 Gala ie and he Uni e e - Ho Gala ie of Ac i e N clei after a frustrating hiatus while it was out of service.
Recognition of the dichotomy in galaxy color has led to another fascinating aspect to AGN hosts. Fro the SDSS and GALEX
surveys, it is clear that the fraction of AGN peaks in the "green valley" between the major sequences of star- forming and
passive galaxies. There are too few objects in the valley for there to be many starbursts superiposed on red galaxies, so most
of the population there must be involved in a one- time transfer from blue to red sequences. What happens then to make feeding
the AGN more efficient? There is also evidence that disk galaxies tend to host less massive black holes, seen in AGN acreting
at a higher Eddington ratio than more massive ones in elliptical galaxies. This could also be connected to the major
transformations in the green valley.
« Jets, superluminal motion, and gamma- ray bursts | Alternate views of active nuclei
Course Home | Bill Keel's Home Page | Image Usage and Copyright Info | UA Astronomy
k email@example.com . a.ed Ls cags 1/09
at hne: 020 .a . a.ed /keel/gala ie /agnho .h ml 20009 4/4 ...
View Full Document
This note was uploaded on 01/15/2012 for the course AY 620 taught by Professor Williamkeel during the Fall '09 term at Alabama.
- Fall '09