Evidence for a black hole from high rotation velocities in a sub-parsec region of NGC4258

Miyoshi, Makoto; Moran, J. M.; Herrnstein, J. R.; Greenhill, L. J.; Nakai, Naomasa; Diamond, P. J.; Inoue, Makoto

doi:10.1038/373127a0

Cited by 1,087 publications

(969 citation statements)

References 18 publications

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“…Most of LLAGN appear to posses thin cold disks. The presence of these disks is deduced convincingly through (i) water maser emission (Miyoshi et al 1995); (ii) infrared "bumps" in the spectral energy distribution of LLAGN (Ho 1999) that are thought (Quataert et al 1999) to be the thermal disk emission (with disk temperatures T < ∼ 10 3 K); and (iii) the prevalence of the double-peaked broad emission lines (e.g. Ho 2003).…”

Section: Cold Disks In Llagn and Sgr A *mentioning

confidence: 99%

X-ray flares from Sgr A^*: Star-disk interactions?

Nayakshin

Cuadra

Sunyaev

2003

A&A

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Abstract. Sgr A * , the putative black hole in our Galactic Center (GC), is extraordinary dim in all frequencies. Apparently the black hole is unable to accrete at the Bondi accretion rate for some reason. Another mystery of Sgr A * is the recently discovered large magnitude and short duration X-ray flares (Baganoff et al. 2001). Here we point out that X-ray flares should be expected from star passages through an inactive (i.e. formerly accreting) disk. There are thousands of stars in Sgr A * stellar cluster, and each star will pass through the disk twice per orbit. A shock hot enough to emit X-rays is formed around the star when the latter is inside the disk. We develop a simple yet somewhat detailed model for the X-ray emission from the shock. The duration of the flares, their X-ray spectra, frequency of events, and weakness of emission in the radio and near infra-red appear to be consistent with the available observations of X-ray flares. We therefore suggest that at least a fraction of the observed flares is due to the star-disk passages. Such star-disk flares are also of interest in the nuclei of nearby inactive galaxies, especially in connection with perspective Constellation-X and XEUS X-ray missions.

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Section: Cold Disks In Llagn and Sgr A *mentioning

confidence: 99%

X-ray flares from Sgr A^*: Star-disk interactions?

Nayakshin

Cuadra

Sunyaev

2003

A&A

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“…Furthermore, since the central active nucleus has been directly detected in X-rays (Makashima et al 1994), it is possible to determine the fractional Eddington luminosity, which is surprisingly small: L/Lg ~ 10 -4 (Neufeld & Maloney 1995). A nice summary of the observations and implications is given by Moran et al (1995). Contrary to assertions elsewhere in the literature, Miyoshi et al (1995) did not derive a density in the disk of TIH 2 = 10 10 cm -3 ; they merely pointed out that this was the maximum possible density the disk could have without quenching the maser emission, as noted above.…”

Section: The Warped Maser Disk Of Ngc 4258mentioning

confidence: 59%

“…A nice summary of the observations and implications is given by Moran et al (1995). Contrary to assertions elsewhere in the literature, Miyoshi et al (1995) did not derive a density in the disk of TIH 2 = 10 10 cm -3 ; they merely pointed out that this was the maximum possible density the disk could have without quenching the maser emission, as noted above.…”

Section: The Warped Maser Disk Of Ngc 4258mentioning

confidence: 59%

Probing Accretion Disks in AGN with Water Masers

Maloney

1997

International Astronomical Union Colloquium

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Abstract.Extremely luminous extragalactic water masers -the socalled "megamasers", with isotropic luminosities of tens to hundreds of solar luminosities -appear to be uniquely associated with active galactic nuclei. The recent survey of Braatz et al. indicates that 20% of Seyfert 2 galaxies have detectable water maser emission. Although originally suggested to arise in shocks, it now seems likely that the masers arise from the irradiation of high-pressure molecular gas by X-rays from the AGN. Quantitative modelling shows that the observed megamaser luminosities can plausibly be produced in this fashion. Both observational limits on the size scales and the high gas pressures required indicate that the water maser emission arises on very small scales, either in a circumnuclear "torus" or the accretion disk itself. In the best-studied case, NCG 4258, the masers are produced in a geometrically thin, warped accretion disk. The maser models can be used to derive quantitative information about the physical conditions in the disk, namely, the mass accretion rate, and therefore the radiative efficiency. I discuss the implications of water maser observations and models for the study of accretion disks and circumnuclear tori in AGN.

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“…Eschewing older data as obsolete, some researchers will consider only the most recent megamaser-based estimate, D=7.6±0.3 Mpc (Humphreys et al 2013). However, when all data are considered, it is evident that megamaser-based estimates for Messier 106 have undergone a systematic increase, from 6.4 Mpc (Miyoshi et al 1995) to 7.2 Mpc (Herrnstein et al 1999), and from 7.3 Mpc , based on private communication with E. M. L. Humphreys) to the current value of 7.6 Mpc by Humphreys et al (2013). Only by having all available data can researchers make informed checks on estimates of the distances to particular galaxies, and estimates of the Hubble constant based on distances to numerous galaxies.…”

Section: How Ned-d Is Formatted and Made Accessiblementioning

confidence: 99%

Redshift-Independent Distances in the Nasa/Ipac Extragalactic Database: Methodology, Content, and Use of Ned-D

Steer¹,

Madore

Mazzarella

et al. 2016

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Estimates of galaxy distances based on indicators that are independent of cosmological redshift are fundamental to astrophysics. Researchers use them to establish the extragalactic distance scale, to underpin estimates of the Hubble constant, and to study peculiar velocities induced by gravitational attractions that perturb the motions of galaxies with respect to the "Hubble flow" of universal expansion. In 2006 the NASA/IPAC Extragalactic Database (NED) began making available a comprehensive compilation of redshift-independent extragalactic distance estimates. A decade later, this compendium of distances (NED-D) now contains more than 100,000 individual estimates based on primary and secondary indicators, available for more than 28,000 galaxies, and compiled from over 2000 references in the refereed astronomical literature. This paper describes the methodology, content, and use of NED-D, and addresses challenges to be overcome in compiling such distances. Currently, 75 different distance indicators are in use. We include a figure that facilitates comparison of the indicators with significant numbers of estimates in terms of the minimum, 25th percentile, median, 75th percentile, and maximum distances spanned. Brief descriptions of the indicators, including examples of their use in the database, are given in an appendix.

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Evidence for a black hole from high rotation velocities in a sub-parsec region of NGC4258

Cited by 1,087 publications

References 18 publications

X-ray flares from Sgr A^*: Star-disk interactions?

X-ray flares from Sgr A^*: Star-disk interactions?

Probing Accretion Disks in AGN with Water Masers

Redshift-Independent Distances in the Nasa/Ipac Extragalactic Database: Methodology, Content, and Use of Ned-D

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Evidence for a black hole from high rotation velocities in a sub-parsec region of NGC4258

Cited by 1,087 publications

References 18 publications

X-ray flares from Sgr A*: Star-disk interactions?

X-ray flares from Sgr A*: Star-disk interactions?

Probing Accretion Disks in AGN with Water Masers

Redshift-Independent Distances in the Nasa/Ipac Extragalactic Database: Methodology, Content, and Use of Ned-D

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Product

Resources

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X-ray flares from Sgr A^*: Star-disk interactions?

X-ray flares from Sgr A^*: Star-disk interactions?