Extended H I Disks in Dust Lane Elliptical Galaxies

The Astronomical Journal (Impact Factor: 4.97). 01/2002; 123:729-744. DOI: 10.1086/338312
Source: arXiv

ABSTRACT We present the results of H I observations of five dust lane elliptical galaxies with the Australia Telescope Compact Array. Two galaxies (NGC 3108 and NGC 1947) are detected, and sensitive upper limits are obtained for the other three. In the two detected galaxies, the H I is distributed in a regular, extended, and warped disklike structure of low surface brightness. Adding data from the literature, we find that several more dust lane elliptical galaxies have regular H I structures. This H I is likely to be a remnant of accretions and/or mergers that took place a considerable time ago and in which a significant fraction of the gas survived to form a disk. The presence of regular H I structures suggests that some mergers lead to galaxies with extended low surface brightness density gas disks. These gas disks will evolve very slowly, and these elliptical galaxies will remain gas-rich for a long period of time. One of the galaxies we observed (NGC 3108) has a very large amount of neutral hydrogen (MHI=4.5×109 Msolar MHI/LB~0.09), which is very regularly distributed in an annulus extending to a radius of ~6 Reff. The kinematics of the H I distribution suggest that the rotation curve of NGC 3108 is flat out to at least the last observed point. We estimate a mass-to-light ratio of M/LB~18 Msolar/LB,solar at a radius of ~6Reff from the center. Several of the galaxies we observed have an unusually low gas-to-dust ratio MHI/Mdust, suggesting that their cold interstellar medium, if present as expected from the presence of dust, may be mainly in molecular rather than atomic form. Based on observations with the Australia Telescope Compact Array (ATCA), which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We review the origin, evolution and physical nature of hot gas in elliptical galaxies and associated galaxy groups. Unanticipated recent X-ray observations with Chandra and XMM indicate much less cooling than previously expected. Consequently, many long-held assumptions need to be reexamined or discarded and new approaches must be explored. Chief among these are the role of heating by active galactic nuclei, the influence of radio lobes on the hot gas, details of the cooling process, possible relation between the hot and colder gas in elliptical galaxies, and the complexities of stellar enrichment of the hot gas.
    Annual Review of Astronomy and Astrophysics 10/2003; · 23.33 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present new planetary nebulae (PNe) positions, radial velocities, and magnitudes for 6 early-type galaxies obtained with the Planetary Nebulae Spectrograph, their two-dimensional velocity and velocity dispersion fields. We extend this study to include an additional 10 early-type galaxies with PNe radial velocity measurements available from the literature, to obtain a broader description of the outer-halo kinematics in early-type galaxies. These data extend the information derived from stellar kinematics to typically up to ~8 Re. The combination of photometry, stellar and PNe kinematics shows: i) good agreement between the PNe number density and the stellar surface brightness in the region where the two data sets overlap; ii) good agreement between PNe and stellar kinematics; iii) that the mean rms velocity profiles fall into two groups: with of the galaxies characterized by slowly decreasing profiles and the remainder having steeply falling profiles; iv) a larger variety of velocity dispersion profiles; v) that twists and misalignments in the velocity fields are more frequent at large radii, including some fast rotators; vi) that outer haloes are characterised by more complex radial profiles of the specific angular momentum-related lambda_R parameter than observed within 1Re; vii) that many objects are more rotationally dominated at large radii than in their central parts; and viii) that the halo kinematics are correlated with other galaxy properties, such as total luminosity, isophotal shape, total stellar mass, V/sigma, and alpha parameter, with a clear separation between fast and slow rotators. Comment: 36 pages, 21 figures, revised version for MNRAS
    Monthly Notices of the Royal Astronomical Society 11/2008; · 5.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent work has identified a population of low-redshift E/S0 galaxies that lie on the blue sequence in color vs. stellar mass parameter space, where spiral galaxies typically reside. While high-mass blue-sequence E/S0s often resemble young merger or interaction remnants likely to fade to the red sequence, we focus on blue-sequence E/S0s with lower stellar masses (< a few 10^10 M_sun), which are characterized by fairly regular morphologies and low-density field environments where fresh gas infall is possible. This population may provide an evolutionary link between early-type galaxies and spirals through disk regrowth. Focusing on atomic gas reservoirs, we present new GBT HI data for 27 E/S0s on both sequences as well as a complete tabulation of archival HI data for other galaxies in the Nearby Field Galaxy Survey. Normalized to stellar mass, the atomic gas masses for 12 of the 14 blue-sequence E/S0s range from 0.1 to >1.0. These gas-to-stellar mass ratios are comparable to those of spiral and irregular galaxies and have a similar dependence on stellar mass. Assuming that the HI is accessible for star formation, we find that many of our blue-sequence E/S0s can increase in stellar mass by 10-60% in 3 Gyr in both of two limiting scenarios, exponentially declining star formation and constant star formation. In a constant star formation scenario, about half of the blue-sequence E/S0s require fresh gas infall on a timescale of <3 Gyr to avoid exhausting their atomic gas reservoirs and evolving to the red sequence. We present evidence that star formation in these galaxies is bursty and likely involves externally triggered gas inflows. Our analysis suggests that most blue-sequence E/S0s are indeed capable of substantial stellar disk growth on relatively short timescales. (abridged) Comment: ApJ, accepted, 26 pages with 12 figures (5 color), 5 tables
    The Astrophysical Journal 11/2009; · 6.73 Impact Factor

Full-text (3 Sources)

Available from
Jul 3, 2014