Versification

Carter, Tim; Sadler, Graham; Branscombe, Peter; Savage, Roger; McMillin, Arnold

doi:10.1093/gmo/9781561592630.article.o008300

Cited by 2 publications

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If NCs have a different velocity dispersion than their host bulge, as is the case for NGC 205 (Carter & Sadler 1990, see their fig. 2), then they could bias measurements of the host bulge’s central velocity dispersion σ.…”

Section: Discussionmentioning

confidence: 89%

An expanded Mbh-σ diagram, and a new calibration of active galactic nuclei masses

Graham

Onken

Athanassoula

et al. 2011

Monthly Notices of the Royal Astronomical Society

425

549

View full text Add to dashboard Cite

We present an updated and improved M bh -σ diagram containing 64 galaxies for which M bh measurements (not just upper limits) are available. Because of new and increased black hole masses at the high-mass end, and a better representation of barred galaxies at the low-mass end, the 'classical' (all morphological type) M bh -σ relation for predicting black hole masses is log (M bh /M ) = (8.13 ± 0.05) + (5.13 ± 0.34)log [σ /200 km s −1 ], with an rms scatter of 0.43 dex. Modifying the regression analysis to correct for a hitherto overlooked sample bias in which black holes with masses <10 6 M are not (yet) detectable, the relation steepens further to give log (M bh /M ) = (8.15 ± 0.06) + (5.95 ± 0.44)log [σ /200 km s −1 ]. We have also updated the 'barless' and 'elliptical-only' M bh -σ relations introduced by Graham and Hu in 2008 due to the offset nature of barred galaxies. These relations have a total scatter as low as 0.34 dex and currently define the upper envelope of points in the M bh -σ diagram. They also have a slope consistent with a value 5, in agreement with the prediction by Silk & Rees based on feedback from massive black holes in bulges built by monolithic collapse.Using updated virial products and velocity dispersions from 28 active galactic nuclei, we determine that the optimal scaling factor f -which brings their virial products in line with the 64 directly measured black hole masses -is 2.8 +0.7 −0.5 . This is roughly half the value reported by Onken et al. and Woo et al., and consequently halves the mass estimates of most high-redshift quasars. Given that barred galaxies are, on average, located ∼0.5 dex below the 'barless' and 'elliptical-only' M bh -σ relations, we have explored the results after separating the samples into barred and non-barred galaxies, and we have also developed a preliminary corrective term to the velocity dispersion based on bar dynamics. In addition, given the recently recognized coexistence of massive black holes and nuclear star clusters, we present the first ever (M bh + M nc )-σ diagram and begin to explore how galaxies shift from their former location in the M bh -σ diagram.

show abstract

Section: Discussionmentioning

confidence: 89%

An expanded Mbh-σ diagram, and a new calibration of active galactic nuclei masses

Graham

Onken

Athanassoula

et al. 2011

Monthly Notices of the Royal Astronomical Society

425

549

View full text Add to dashboard Cite

show abstract

“…We selected dE galaxies with K ‐band magnitudes to lie within or close to the ‘gap’ reported by Forbes et al (2008). These galaxies were further constrained to have no nucleus (dE) or only a small nuclear (dE,N) component as a nuclear cluster will have its own dynamical properties distinct from the underlying galaxy (Carter & Sadler 1990; Geha, Guhathakurta & van der Marel 2002; Geha et al 2003).…”

Section: Sample Selectionmentioning

confidence: 99%

Bridging the gap between low- and high-mass dwarf galaxies

Forbes

Spitler

Graham

et al. 2011

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

While the dark matter content within the most‐massive giant and smallest dwarf galaxies has been probed – spanning a range of over one million in mass – an important observational gap remains for galaxies of intermediate mass. This gap covers K‐band magnitudes of approximately −16 > MK > −18 mag (for which dwarf galaxies have B−K∼ 2). On the high‐mass side of the gap are dwarf elliptical (dE) galaxies that are dominated by stars in their inner regions. While the low‐mass side includes dwarf spheroidal (dSph) galaxies that are dark matter dominated and ultracompact dwarf (UCD) objects that are star‐dominated. Evolutionary pathways across the gap have been suggested but remain largely untested because the ‘gap’ galaxies are faint, making dynamical measurements very challenging. With long exposures on the Keck telescope using the Echelle Spectrograph and Imager instrument, we have succeeded in bridging this gap by measuring the dynamical mass for five dwarf galaxies with MK∼−17.5 (MB∼−15.5). With the exception of our brightest dwarf galaxy, they possess relatively flat velocity dispersion profiles of around 20 km s−1. By examining their 2D scaling relations and 3D fundamental manifold, we found that the sizes and velocity dispersions of these gap galaxies reveal continuous trends from dE to dSph galaxies. We conclude that low‐luminosity dE galaxies are dominated by stars, not by dark matter, within their half light radii. This finding can be understood if internal feedback processes are operating most efficiently in gap galaxies, gravitationally heating the centrally located dark matter to larger radii, whereas external environmental processes, which can strip away stars, have a greater influence on dSph galaxies, resulting in their higher dark matter fractions. UCD objects appear to be more similar to massive compact star clusters than to small galaxies. Our dynamical study of low‐mass dE galaxies provides further constraints on the processes that shape some of the smallest and most‐numerous galaxies in the Universe.

show abstract

Versification

Cited by 2 publications

References 0 publications

An expanded Mbh-σ diagram, and a new calibration of active galactic nuclei masses

An expanded Mbh-σ diagram, and a new calibration of active galactic nuclei masses

Bridging the gap between low- and high-mass dwarf galaxies

Contact Info

Product

Resources

About