1 / 30

DOVE TROVARE GLI ARTICOLI:

DOVE TROVARE GLI ARTICOLI: Preprint service (per articoli non ancora pubblicati, o conference proceedings): http://xxx.lanl.gov/archive/astro-ph (o fate una ricerca su Google su “Astrophysics preprints” per trovare un mirror site)

kamali
Download Presentation

DOVE TROVARE GLI ARTICOLI:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. DOVE TROVARE GLI ARTICOLI: • Preprint service (per articoli non ancora pubblicati, o conference proceedings): http://xxx.lanl.gov/archive/astro-ph (o fate una ricerca su Google su “Astrophysics preprints” per trovare un mirror site) • Articoli pubblicati: ADS astronomy and Astrophysics Abstract Service http://adsabs.harvard.edu/abstract_service.html

  2. SIGRAV Graduate School in Contemporary Relativity and Gravitational Physics Laura Ferrarese Rutgers University Lecture 3: Gas Dynamics

  3. Lecture 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

  4. Historical 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

  5. Ionized gas streamers(< 1.7) Neutral circumstellar ring (1.7 < R < 9pc) - dominated predominantly by circular motion Mass estimate from the stellar velocity dispersion Mass distribution from the 2m stellar brightness profile Models with a 3.0106 and 2.5106 central mass concentration. Historical Perspective

  6. Historical 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).

  7. Palomar 0.9inch telescope, BVR composite image A 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.

  8. NGC 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

  9. The Importance of H20 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: =0.00060.0003, 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

  10. From Herrnstein, Greenhill & Moran 1996, ApJ, 446, L17 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 radius 9. the central mass. • The observables are: • relative position of the clouds in the sky, • line of sight velocity and • 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).

  11. Other SBH Detections from H2O Masers • Circinus (Greenhill et al. 2003, astro-ph/0302533): MBH=(1.70.3)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.

  12. Other SBH Detections from H2O Masers • 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.

  13. Water Maser Surveys How 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).

  14. Water 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).

  15. A Complete Census of H20 Maser Detections GALAXY REFERENCE AGN TYPE DISK? VLBI? M51 Hagiwara et al. 2001 Seyfert 2 perhaps no NGC253 Nakai et al. 1995 Starburst no NGC1052 Braatz et al. 1996 LINER no NGC 1068 Greenhill et al. 1996 Seyfert 2 yes yes, disk is self gravitating. NGC1386 Braatz et al. 1996 Seyfert 2 no NGC2639 Braatz et al. 1996 Seyfert 2 no NGC2824 Greenhill et al. 2003 ? no NGC2979 Greenhill et al. 2003 Seyfert 2 no NGC 3079 Trotter et al. 1998 Seyfert 2 no NGC3735 Greenhill et al. 1997 Seyfert 2 no NGC4258 Greenhill et al. 1995 Seyfert 2 yes yes, best case for a SBH NGC4945 Greenhill et al. 1997 Seyfert 2 yes no NGC5347 Braatz et al. 1996 Seyfert 2 no NGC5506 Braatz et al. 1996 Seyfert 2 no NGC5643 Greenhill et al. 2003 Seyfert 2 no NGC6300 Greenhill et al. 2003 Seyfert 2 no NGC6929 Greenhill et al. 2003 Seyfert 2 yes no IC1481 Braatz et al. 1996 LINER no IC2560 Braatz et al. 1996 Seyfert 2 no Mrk1 Braatz et al. 1996 Seyfert 2 no Mrk1210 Braatz et al. 1996 Seyfert 2 no Mrk1419 Henkel et al. 2002 Seyfert 2 yes no Circinus Greenhill et al. 2003 Seyfert 2 yes yes, good SBH mass estimate ESO269+G012 Greenhill et al. 2003 Seyfert 2 yes no ESO103-G35 Braatz et al. 1996 Seyfert 2 no IRASF19370-0131 Greenhill et al. 2003 Seyfert 2 no IRASF01063-8034 Greenhill et al. 2002 Seyfert 2 no

  16. Larger 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.

  17. Disks and Radio Jets

  18. Emission 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)

  19. Gas Motion in the M87 Nucleus

  20. Gas Motion in the M87 Nucleus From Macchetto et al. 1997, ApJ, 489, 579

  21. Gas Motion in the M84 Nucleus

  22. Analysis of Dust Disk Kinematics • Procedure: • 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. • Construct the central potential, as the sum of the stellar potential, disk potential and the potential of a central point mass. • 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. • Project the circular velocity for a grid of disk inclination and position angles. • Compare to the observables, and iterate until the potential and geometrical parameters of the disk than minimizes the 2 of the fit are found.

  23. Dust Disk i   r Kinematical Axis Analysis 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. • M(r) is the total mass within radius r, including: • a central massM • the stellar mass (M/L)(r,,)drdd • the disk mass (known from the optical depth analysis) • Unknowns are: • the central mass M • the stellar mass to light ratio M/L • the kinematical position angle  • the disk inclination angle i

  24. Analysis of Gas Disk Kinematics: NGC 4261 • The total mass to light ratio within 0.1 arcsec is 2100 M/L

  25. Analysis of Gas Disk Kinematics: NGC 4261 Dust Disk Stellar Isophotes Inner Disk (from the dynamical models)

  26. Gas 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)

  27. Incidence 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%

  28. A Census of SBH Detection From Gas 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

  29. Points 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.

  30. Suggested 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

More Related