Mean morphological types of bright galaxies

Buta, Ronald J.; Mitra, Sourav; Vaucouleurs, G. de; Corwin, H. G.

doi:10.1086/116838

Cited by 81 publications

(109 citation statements)

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“…The optical colors of the rings were determined through a 10 diameter circular aperture placed on the brightest parts of the rings along its major axes. In the large ring we found the following colors at the indicated positions with respect to the nucleus: previous section), and its extinction and redshift corrected colors (B − V ≈ 0.5, V − R ≈ 0.4) are typical for Sc-Scd spirals (Buta et al 1994;Buta & Williams 1995) and similar to those of PRG rings (Reshetnikov et al 1994(Reshetnikov et al , 1995.…”

Section: Ringssupporting

confidence: 55%

Galaxy transmutations: The double ringed galaxy ESO 474-G26

Решетников

Bournaud²,

Combes³

et al. 2005

A&A

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Abstract. Surface photometry and a 21 cm H  line spectrum of the giant double-ringed galaxy ESO 474-G26 are presented.The morphology of this system is unique among the 30 000 galaxies with B ≤15. m 5. Two almost orthogonal optical rings with diameters of 60 and 40 kpc surround the central body (assuming H 0 = 70 km s −1 Mpc −1 ). The outer one is an equatorial ring, while the inner ring lies in a nearly polar plane. The rings have blue optical colors typical of late-type spirals. Both appear to be rotating around the central galaxy, so that this system can be considered as a kinematically confirmed polar ring galaxy. Its observational characteristics are typical of galaxy merger remnants. Although the central object has a surface brightness distribution typical of elliptical galaxies, it has a higher surface brightness for its effective radius than ordinary ellipticals. Possible origins of this galaxy are discussed and numerical simulations are presented that illustrate the formation of the two rings in the merging process of two spiral galaxies, in which the observed appearance of ESO 474-G26 appears to be a transient stage.

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Section: Ringssupporting

confidence: 55%

Galaxy transmutations: The double ringed galaxy ESO 474-G26

Решетников

Bournaud²,

Combes³

et al. 2005

A&A

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“…1 For the Galaxy the mean color index for Sbc type was used (Buta et al, 1994). A straight line reproduces model relation obtained by Bell, de Jong (2001) for old stellar systems with different present-day star formation rate (SFR) using modified (bottom-light) Salpeter initial mass function (IMF).…”

Section: Resultsmentioning

confidence: 78%

Gravitational stability and dynamical overheating of galactic stellar disks

Засов¹,

Хоперсков

Saburova³

2011

Astron. Lett.

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We use the marginal stability condition for galactic disks and the stellar velocity dispersion data published by different authors to place upper limits on the disk local surface density at two radial scalelengths R = 2h. Extrapolating these estimates, we constrain the total mass of the disks and compare these estimates to those based on the photometry and color of stellar populations.The comparison reveals that the stellar disks of most of spiral galaxies in our sample cannot be substantially overheated and are therefore unlikely to have experienced a significant merging event in their history. The same conclusion applies to some, but not all of the S0 galaxies we consider. However, a substantial part of the early type galaxies do show the stellar velocity dispersion well in excess of the gravitational stability threshold suggesting a major merger event in the past. We find dynamically overheated disks among both seemingly isolated galaxies and those forming pairs. The ratio of the marginal stability disk mass estimate to the total galaxy mass within four radial scalelengths remains within a range of 0.4-0.8. We see no evidence for a noticeable running of this ratio with either the morphological type or color index.

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“…The figure shows that Q g has some dependence on surface brightness in the sense that at higher surface brightnesses ( 0 e0 < 13:0 mag arcmin À2 ), there is an upper envelope above which few galaxies are found, while at lower surface brightnesses, the selection criteria of our sample cause many low-luminosity, lower surface brightness galaxies (such as the ''DDO dwarfs,'' which have surface brightnesses in the range of 13-17 mag arcmin À2 ; de Vaucouleurs, de Vaucouleurs, & Buta 1981) to be excluded. The surface brightness effects are built into the type dependence we see in hQ g i, since mean effective surface brightness strongly depends on type (de Vaucouleurs & Buta 1983;Buta et al 1994). Earlytype spirals have a higher mean effective surface brightness on average, because of a greater bulge contribution on average.…”

Section: The Perturbation Strength Q Gmentioning

confidence: 99%

Comparison of Bar Strengths and Fractions of Bars in Active and Nonactive Galaxies

Laurikainen

Salo

Buta

2004

ApJ

143

175

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Gravitational perturbation strengths and bar fractions in active and nonactive galaxies are compared using the Ohio State University Bright Galaxy Survey, which forms a statistically well defined sample of 180 disk galaxies. Bar fractions are studied using (1) the optical and near-IR classification of bars made by Eskridge and coworkers in 2002 and (2) our own bar classification based on Fourier decomposition of near-IR images (Fourier bars). The gravitational perturbation strengths are calculated using the bar torque method, taking the maximum ratio Q g of the tangential force to the mean background radial force as a measure of the nonaxisymmetric perturbation. In addition, two-dimensional bulge-disk-bar decomposition is used to study the properties of bulges of the sample galaxies. In the near-IR, Seyfert galaxies, LINERs, and H ii/starburst galaxies were found to have a similar fraction, 72%, of Fourier bars (or SB-type bars), compared to 55% in the nonactive galaxies. However, if SABtype bars are also included, practically all (95%) H ii/starburst galaxies have bars. In addition, a large fraction (34%) of bars in LINERs are obscured by dust in the optical region. We find that bars in early-type galaxies are at the same time long and massive and have weak perturbation strengths. Weak perturbation strengths can be explained by dilution of the nonaxisymmetric forces by the massive bulges: for a bulge-to-disk mass ratio B=D ranging from 0 to 1, the dilution may reduce Q g from as high as 0.6 to as low as 0.1. On the other hand, bar length (relative to disk scale length) is not correlated with B=D, contrary to expectation. Seyfert-or LINER-type nuclear activity is present in most galaxies that have thin and thick planar bar components, whereas nuclear activity does not appear in those late-type galaxies that have extremely massive bars and strong perturbation strengths.

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Mean morphological types of bright galaxies

Cited by 81 publications

References 0 publications

Galaxy transmutations: The double ringed galaxy ESO 474-G26

Galaxy transmutations: The double ringed galaxy ESO 474-G26

Gravitational stability and dynamical overheating of galactic stellar disks

Comparison of Bar Strengths and Fractions of Bars in Active and Nonactive Galaxies

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