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Date and Time of the Query: 2019-06-24 T18:45:54 PDT
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For refcode 2010ApJ...723...54K:
Retrieve 22 NED objects in this reference.
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NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
2010ApJ...723...54K Bulgeless Giant Galaxies Challenge Our Picture of Galaxy Formation by Hierarchical Clustering Kormendy, John; Drory, Niv; Bender, Ralf; Cornell, Mark E. Abstract. To better understand the prevalence of bulgeless galaxies in the nearby field, we dissect giant Sc-Scd galaxies with Hubble Space Telescope (HST) photometry and Hobby-Eberly Telescope (HET) spectroscopy. We use the HET High Resolution Spectrograph (resolution R = {lambda}/FWHM ~= 15, 000) to measure stellar velocity dispersions in the nuclear star clusters and (pseudo)bulges of the pure-disk galaxies M 33, M 101, NGC 3338, NGC 3810, NGC 6503, and NGC 6946. The dispersions range from 20 +/- 1 km s^-1^ in the nucleus of M 33 to 78 +/- 2 km s^-1^ in the pseudobulge of NGC 3338. We use HST archive images to measure the brightness profiles of the nuclei and (pseudo)bulges in M 101, NGC 6503, and NGC 6946 and hence to estimate their masses. The results imply small mass-to-light ratios consistent with young stellar populations. These observations lead to two conclusions. (1) Upper limits on the masses of any supermassive black holes are M_blackhole_ <~ (2.6 +/- 0.5) x 10^6^ M_sun_ in M 101 and M_blackhole_ <~ (2.0 +/- 0.6) x 10^6^ M_sun_ in NGC 6503. (2) We show that the above galaxies contain only tiny pseudobulges that make up <~3% of the stellar mass. This provides the strongest constraints to date on the lack of classical bulges in the biggest pure-disk galaxies. We inventory the galaxies in a sphere of radius 8 Mpc centered on our Galaxy to see whether giant, pure-disk galaxies are common or rare. We find that at least 11 of 19 galaxies with V_circ_ > 150 km s^-1^, including M 101, NGC 6946, IC 342, and our Galaxy, show no evidence for a classical bulge. Four may contain small classical bulges that contribute 5%-12% of the light of the galaxy. Only four of the 19 giant galaxies are ellipticals or have classical bulges that contribute ~1/3 of the galaxy light. We conclude that pure-disk galaxies are far from rare. It is hard to understand how bulgeless galaxies could form as the quiescent tail of a distribution of merger histories. Recognition of pseudobulges makes the biggest problem with cold dark matter galaxy formation more acute: How can hierarchical clustering make so many giant, pure-disk galaxies with no evidence for merger-built bulges? Finally, we emphasize that this problem is a strong function of environment: the Virgo cluster is not a puzzle, because more than 2/3 of its stellar mass is in merger remnants. Key words: galaxies: evolution, galaxies: formation, galaxies: individual: M 33 NGC 3338 NGC 3810 NGC 5457 NGC 6503 NGC 6946, galaxies: nuclei, galaxies: photometry, galaxies: structure
Retrieve 22 NED objects in this reference.
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