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SIGRAV Graduate School in Contemporary SIGRAV Graduate School in Contemporary

Relativity and Gravitational PhysicsRelativity and Gravitational Physics

Laura FerrareseLaura FerrareseRutgers UniversityRutgers University

Lecture 3: Gas DynamicsLecture 3: Gas Dynamics

Lecture OutlineLecture OutlineLecture OutlineLecture Outline Historical Perspective: The Milky Way (again!)

Water Maser Disks:

A detailed look at NGC 4258 Incidence of water masers in galactic nuclei

HST studies of dust and gas disks

A detailed look at NGC 4261 Biases and Systematics of the Dynamical Models Incidence of nuclear dust/gas Disks

Historical PerspectiveHistorical PerspectiveHistorical PerspectiveHistorical Perspective Historically, the kinematics of ionized and neutral gas near (< 8pc) the

galactic center presented the first indication for the existence of a central mass concentration (early review and references in Genzel & Townes 1985 ARA&A 25, 377).

VLA 6cm image of the inner few pcs

Historical PerspectiveHistorical PerspectiveHistorical PerspectiveHistorical Perspective

Mass distribution from the 2m stellar brightness profile

Models with a 3.0106 and 2.5106 central mass concentration.

Mass estimate from the stellar velocity dispersion

Neutral circumstellar ring (1.7 < R < 9pc) - dominated predominantly by circular motion

Ionized gas streamers(< 1.7)

Historical PerspectiveHistorical PerspectiveHistorical PerspectiveHistorical Perspective Gas kinematics, however, has traditionally been dismissed in fear that

forces other than gravity might push the gas around, and therefore that gas motion might not be a good tracer of mass:

“..as usual it is not certain that gas velocities measure mass” (Kormendy & Richstone 1995, ARA&A, 33, 581, referring to the maser disk in NGC 4258 - no less!).

Gas dynamical mass estimates started to draw serious attention with the discovery of regular, small nuclear disks of gas and dust in a significant fraction of early type galaxies (Jaffe et al. 1993, Nature, 364, 213; Ford et al. 1994; Ferrarese, Ford & Jaffe).

A Very Special Case: NGC 4258A Very Special Case: NGC 4258A Very Special Case: NGC 4258A Very Special Case: NGC 4258 NGC 4258 was one of the 12 galaxies originally identified by Seyfert. Based

on its spectral line profiles, NGC 4258 is a Seyfert 2 galaxy, i.e. the active nucleus is hidden, because of projection effects, by the surrounding dust torus.

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Palomar 0.9inch telescope,BVR composite image

NGC 4258NGC 4258NGC 4258NGC 4258 Nakai et al (1993) discovered high velocity H20 maser emission at v~1000

km/s relative to the galaxy’s systemic velocity.

Data taken with the Effelsberg 100m telescope; from Greenhill et al. 1995, A&A, 304, 21

The Importance of HThe Importance of H220 Masers0 MasersThe Importance of HThe Importance of H220 Masers0 Masers What’s the relevance of H2O emission

in the SBH context?

At 1.35cm, water maser observations can be carried out at exceptional spatial and velocity resolution with the VLBI: =0.00060.0003, v= 0.2 km/s

VLBI spatially resolved observations of water maser emission in NGC 4258 have allowed to

measure the mass of the central SBH with unparalleled precision

measure the distance to the galaxy with unparalleled precision, thus providing a potentially very important test of the extragalactic distance scale.

Myioshi et al. 1995,Nature, 373, 127

A (More Complex) Model NGC 4258.A (More Complex) Model NGC 4258.A (More Complex) Model NGC 4258.A (More Complex) Model NGC 4258. The degree of warping can be constrained: a warped

disk can be modeled using nine parameters, namely :

1-2. the (x,y) positions of the center of mass,

3. the galaxy systemic velocity, 4-5. the inclination as a function of radius

(2 parameters) 6-8. the position angle as a function of

radius9. the central mass.

The observables are: 1. relative position of the clouds in the sky, 2. line of sight velocity and 3. acceleration

for each of the maser clouds.

Therefore the problem is fully constrained. From top to bottom: Position angle changes with radius; Both position angle and inclination change with

radius best fitting flat disk (can be excluded because it

predicts a systemic velocity in significant disagreement with the observed value).

From Herrnstein, Greenhill & Moran 1996, ApJ, 446, L17

Other SBH Detections from HOther SBH Detections from H22O O MasersMasers

Other SBH Detections from HOther SBH Detections from H22O O MasersMasers

Circinus (Greenhill et al. 2003, astro-ph/0302533): MBH=(1.70.3)106 M

The edge-on disk extends from 0.1 to 0.4 pc. The rotation curve is nearly Keplerian, although the disk is probably fairly massive (up to 25% the central mass) and therefore self-gravity is not negligible.

A second population of masers traces a wide angle outflow up to 1pc from the central engine.

Other SBH Detections from HOther SBH Detections from H22O O MasersMasers

Other SBH Detections from HOther SBH Detections from H22O O MasersMasers

NGC 1068 (Greenhill et al. 1996, ApJ, 472, L21): MBH~107 M

The rotation curve is sub-Keplerian, the disk might be self-gravitating and there might be a significant turbulent component.

Water Maser SurveysWater Maser SurveysWater Maser SurveysWater Maser SurveysHow common are water masers?

Braatz, Wilson & Henke 1996, ApJS, 106, 51

354 galaxies, including a distance and magnitude limited sample of Seyfert and LINER galaxies with cz< 7000 km /s, plus some active galaxies, including radio galaxies, at higher redshift. Detection rate is 7% among 216 Seyfert 2 nuclei and LINERs, with no masers occurring in Seyfert 1 nuclei (Braatz, Wilson, & Henkel 1997, ApJS, 110, 321).

Greenhill et al. 1997, ApJ, 486, L15

26 AGNs observed with the 70m antenna of the NASA Deep Space Network. One detection (NGC3735), with emission at systemic velocity only (4% detection efficiency).

Greenhill et al. 2002, ApJ, 565, 836

131 AGNs observed at the Parkes Observatory. One detection, with emission at systemic velocity only (1% detection efficiency).

Water Maser SurveysWater Maser SurveysWater Maser SurveysWater Maser Surveys Greenhill et al. 2003, ApJ, 582, L11:

survey of 160 nearby (cz< 8100 km/s) AGNs with the 70m antenna of the NASA Deep Space Network in Australia. Larger sensitivity and wider wavelength coverage than previous surveys.

7 new sources detected (4% detection rate), with two sources exhibiting high velocity masers (figure at right).

Besides the fact that water maser emission is not detected in Seyfert 1 galaxies, no strong correlations have yet been found between maser emission and the global properties of the host galaxies, although where X-ray measurements are available, all known H2O masers lie in galaxies with large X-ray obscuring columns, 1023 cm-2 (Braatz et al. 1997, ApJS, 110, 321).

A Complete Census of H20 Maser A Complete Census of H20 Maser DetectionsDetections

A Complete Census of H20 Maser A Complete Census of H20 Maser DetectionsDetectionsGALAXY REFERENCE AGN TYPE DISK? VLBI?

M51 Hagiwara et al. 2001 Seyfert 2 perhaps noNGC253 Nakai et al. 1995 Starburst noNGC1052 Braatz et al. 1996 LINER noNGC 1068 Greenhill et al. 1996 Seyfert 2 yes yes, disk is self

gravitating.NGC1386 Braatz et al. 1996 Seyfert 2 noNGC2639 Braatz et al. 1996 Seyfert 2 noNGC2824 Greenhill et al. 2003 ? noNGC2979 Greenhill et al. 2003 Seyfert 2 noNGC 3079 Trotter et al. 1998 Seyfert 2 noNGC3735 Greenhill et al. 1997 Seyfert 2 noNGC4258 Greenhill et al. 1995 Seyfert 2 yes yes, best case for a SBHNGC4945 Greenhill et al. 1997 Seyfert 2 yes noNGC5347 Braatz et al. 1996 Seyfert 2 noNGC5506 Braatz et al. 1996 Seyfert 2 noNGC5643 Greenhill et al. 2003 Seyfert 2 noNGC6300 Greenhill et al. 2003 Seyfert 2 noNGC6929 Greenhill et al. 2003 Seyfert 2 yes noIC1481 Braatz et al. 1996 LINER noIC2560 Braatz et al. 1996 Seyfert 2 noMrk1 Braatz et al. 1996 Seyfert 2 noMrk1210 Braatz et al. 1996 Seyfert 2 noMrk1419 Henkel et al. 2002 Seyfert 2 yes noCircinus Greenhill et al. 2003 Seyfert 2 yes yes, good SBH mass

estimateESO269+G012 Greenhill et al. 2003 Seyfert 2 yes noESO103-G35 Braatz et al. 1996 Seyfert 2 noIRASF19370-0131 Greenhill et al. 2003 Seyfert 2 noIRASF01063-8034 Greenhill et al. 2002 Seyfert 2 no

Larger Scale Gas/Dust DisksLarger Scale Gas/Dust DisksLarger Scale Gas/Dust DisksLarger Scale Gas/Dust Disks A small (102 pc), nuclear dust/gas disk was first discovered in the E2 galaxy NGC

4261, using the Hubble Space Telescope (Jaffe et al. 1993, Nature, 364, 213)

Why are the disks intriguing? They are very regular, suggesting a simple dynamical structure. They are very thin, suggesting that the kinematics of the dust and gas are

dominated by rotation. They contain ionized gas, which produces easily detectable emission lines,

which can be used to study the disks kinematics They are always found in low-luminosity AGNs (radio galaxies and

LINERS). In all cases, the minor axis of the disk is roughly aligned with the radio jets, suggesting a causal connection between the disks and the central engines.

The origin and dynamical evolution of the disks are not known, but hold clues to the evolution of their host galaxies.

Disks and Radio JetsDisks and Radio JetsDisks and Radio JetsDisks and Radio Jets

Emission Lines from the DiskEmission Lines from the DiskEmission Lines from the DiskEmission Lines from the Disk The line profiles are symmetric,

excluding a one-direction outflow The largest velocities are measured

along the major axis of the disk, excluding a bi-directional outflow (which would produce the largest velocities along the minor axis, unless the outflow is misaligned with the radio structure)

The forbidden lines are broad, implying that the lines are broadened by rotation.

NGC4261 (Ferrarese, Ford & Jaffe 1996)

Gas Motion in the M87 NucleusGas Motion in the M87 NucleusGas Motion in the M87 NucleusGas Motion in the M87 Nucleus

Gas Motion in the M87 NucleusGas Motion in the M87 NucleusGas Motion in the M87 NucleusGas Motion in the M87 NucleusFrom Macchetto et al. 1997, ApJ, 489, 579

Gas Motion in the M84 NucleusGas Motion in the M84 NucleusGas Motion in the M84 NucleusGas Motion in the M84 Nucleus

Analysis of Dust Disk Analysis of Dust Disk KinematicsKinematics

Analysis of Dust Disk Analysis of Dust Disk KinematicsKinematics

Procedure:

1) given the observed surface brightness profile, build an axisymmetric mass model for the stellar population, under the assumption of a (constant) mass to light ratio. Dust obscuration needs to be taken into account.

2) Construct the central potential, as the sum of the stellar potential, disk potential and the potential of a central point mass.

3) Derive the circular velocity corresponding to the potential. Notice that this step is much simplified compared to the case in which stellar kinematics is involved: the assumption here is that the system under study is 2-dimensional and dominated by rotation.

4) Project the circular velocity for a grid of disk inclination and position angles.

5) Compare to the observables, and iterate until the potential and geometrical parameters of the disk than minimizes the 2 of the fit are found.

Analysis of Gas Disk KinematicsAnalysis of Gas Disk KinematicsAnalysis of Gas Disk KinematicsAnalysis of Gas Disk Kinematics The observed (projected) velocity is a function of location within the disk,

and of the inclination angle of the disk relative to the line of sight. We can also allow for the possibility that the kinematical axis is not aligned with the major axis of the large scale dust disk.

€

V 2(r,θ;φ,i) =GM(r)

r

sin2 i cos3 i

cos(θ + φ)[cos2 i + tan2(θ + φ)]3 / 2

i

r

Kinematical Axis

Dust Disk M(r) is the total mass within radius r, including:1) a central mass M2) the stellar mass

(M/L)(r,,)drdd3) the disk mass (known from

the optical depth analysis)

Unknowns are:

I. the central mass MII. the stellar mass to light ratio

M/LIII. the kinematical position

angle IV. the disk inclination angle i

Analysis of Gas Disk Kinematics: Analysis of Gas Disk Kinematics: NGC 4261NGC 4261

Analysis of Gas Disk Kinematics: Analysis of Gas Disk Kinematics: NGC 4261NGC 4261

The total mass to light ratio within 0.1 arcsec is 2100 M/L

Analysis of Gas Disk Kinematics: Analysis of Gas Disk Kinematics: NGC 4261NGC 4261

Analysis of Gas Disk Kinematics: Analysis of Gas Disk Kinematics: NGC 4261NGC 4261

Dust Disk

Stellar IsophotesInner Disk (fromthe dynamicalmodels)

Gas Disks: Potential ProblemsGas Disks: Potential ProblemsGas Disks: Potential ProblemsGas Disks: Potential Problems There are instrumental effects which need to be accounted for in the preceding

analysis, or biases can arise. In particular, smearing due to the finite width of the slit, and PSF blurring can be important (Maciejewski & Binney 2001) but, thankfully, easily quantifiable.

There are, however, several other issues which are difficult to quantify given the quality of the available data. Is the disk structure really as simple as it appears? Probably not! In particular, we

need to account for: Presence of a significant intrinsic velocity dispersion in all of the disks, which may not be

gravitational in nature (Harms et al. 1994, Ferrarese, Ford & Jaffe 1996, Ferrarese & Ford 1999, Cappellari et al. 2002, Verdoes Kleijn et al. 2002, etc..)

Presence of warps in the disk (Ferrarese, Ford & Jaffe 1996, Ferrarese & Ford 1999, Cappellari et al. 2002).

Stellar and gas dynamical estimates of MBH have been carried out in only one galaxy, IC1459 (Verdoes Kleijn et al. 2000, Cappellari et al. 2002)

MBH(gas) = (0.4 1.0) 109 M (depending on the assumptions made for the gas

velocity field) MBH(stars) = (4.0 6.0) 109 M (using 2I axisymmetric modeling of ground based

data) MBH(stars) = (2.6 1.1) 109 M (using 3I modeling of HST/STIS data with

N0/Nc=2.0)

Incidence of Dust DisksIncidence of Dust DisksIncidence of Dust DisksIncidence of Dust Disks How common are dust disks?

Van Dokkum & Franx (1995, AJ, 110, 2027): 64 E-type galaxies from HST archive Incidence of dust 49% Incidence of dust disks 13%

Rest et al. (2001, AJ, 121, 2431): 67 E-type galaxies drawn from a volume a magnitude limited sample Incidence of dust 43% Incidence of dust disks 15%

Laine et al. (2003, AJ, 125, 428): 81 BCGs from HST snapshot program Incidence of dust 38% Incidence of dust disks 14%

A Census of SBH Detection From A Census of SBH Detection From Gas DisksGas Disks

A Census of SBH Detection From A Census of SBH Detection From Gas DisksGas Disks

Galaxy Type Distance MBH + - Reference

(Mpc) (108 solar masses)

N4261 E2 33.0 5.4 1.2 1.2 Ferrarese et al. 1996, ApJ, 470, 444

N4342 S0 16.7 3.3 1.9 1.1 Cretton & v.d. Bosch 1999, ApJ, 514, 704

N4374 E1 18.7 17 12 6.7 Bower et al. 1998, ApJ, 492, L111

N4486 E0pec 16.7 35.7 10.2 10.2 Macchetto et al. 1997, ApJ, 489, 579

N6251 E 104 5.9 2.0 2.0 Ferrarese & Ford 1999, ApJ, 515, 58

N7052 E 66.1 3.7 2.6 1.5 v.d. Marel & v.d. Bosch 1998, AJ, 116, 2220

M81 SA(s)ab 3.9 0.70 0.2 0.1 Devereux et al. 2003, AJ, 125, 1226

N2787 SB(r)0 7.5 0.90 6.89 0.69 Sarzi et al. 2001, ApJ, 550, 65

N3245 SB(s)b 20.9 2.1 0.5 0.5 Barth et al. 2001, ApJ, 555, 685

N5128 S0pec 3.5 2.0 3.0 1.4 Marconi et al. 2001, ApJ, 549, 915

CygA E 240 25.0 7.0 7.0 Tadhunter et al. 2003, astro-ph/0302513

Points to Bring HomePoints to Bring HomePoints to Bring HomePoints to Bring Home Gas dynamics present a powerful alternative to stellar dynamical studies, at

least in low luminosity AGNs residing in early type galaxies (optical nuclear dust disks) and Seyfert 2 galaxies (water maser disks).

About 15% of all early type galaxies host nuclear dust disks, while perhaps 4% to 7% of Seyfert 2 (and some LINERS) host water maser disks.

Gas dynamics is subject to systematic biases which are completely independent from those afflicting stellar dynamical studies (or, as we will see, reverberation mapping studies). Comparing mass estimates for the same galaxy using different methods can yield useful insights onto the nature of such systematics.

Gas dynamics and stellar dynamics are somewhat complementary. For instance, gas dynamics allow to probe large, spherical, pressure supported ellipticals, or late type spirals and AGNs which are problematic for stellar dynamical studies.

The study of nuclear dust disks is interesting beyond the SBH mass issue. The disks can tell us about the history of their host galaxies and the feeding habits of the central monster.

Suggested ReadingsSuggested ReadingsSuggested ReadingsSuggested Readings

Water masers (review, although a little dated)Moran et al. 1999, in the Journal of Astronomy and

Astrophysics (India), proceedings of the Meeting on the Physics

of Black Holes, astro-ph/0002085,

Nuclear Dust Disks: M87, the Saga Continues…

Ford et al. 1994, ApJ, 435, L27

Harms et al. 1994, ApJ, 435, L35

Macchetto et al. 1997, ApJ, 489, 579