Optical Spectroscopy of the Central Regions of Bright Barred Spiral Galaxies (original) (raw)
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The structure of spiral galaxies -- I. Near-infrared properties of bulges, discs and bars
Monthly Notices of the Royal Astronomical Society, 1998
We present data for a sample of 45 spiral galaxies over a range of Hubble types, imaged in the near-IR J and K bands. Parameters are calculated describing the bulge, disk and bar K-band light distributions, and we look for correlations showing the interrelation between these components. We find that bulge profiles are not well-fitted by the classic de Vaucouleurs profile, and that exponential or R 1/2 fits are preferred. Bulge-to-disk ratio correlates only weakly with Hubble type. Many of the galaxies show central reddening of their J-K colours, which we interpret as due to nuclear starbursts or dusty AGN. We define a new method for measuring the strength of bars, which we call Equivalent Angle. We stress that this is better than the traditional bar-interbar contrast, as it is not subject to seeing and resolution effects. Bars are found in 40 of the 45 galaxies, 9 of which had been previously classified as unbarred. Bar strengths are found not to correlate with disk surface brightness or the presence of near neighbours, but a tendency is found for the most strongly barred galaxies to lie within a restricted, intermediate range of bulge-to-disk ratio. Bar light profiles are found to be either flat or exponentially decreasing along their long axes, with profile type not correlating strongly with Hubble type. Bar short axis profiles are significantly asymmetric, with the steeper profile being generally on the leading edge, assuming trailing arms. In the K-band we find bars with higher axial ratios than have been found previously in optical studies.
The structure of spiral galaxies - I. Near-infrared properties of bulges, disks and bars
1998
We present data for a sample of 45 spiral galaxies over a range of Hubble types, imaged in the near-IR J and K bands. Parameters are calculated describing the bulge, disk and bar K-band light distributions, and we look for correlations showing the interrelation between these components. We find that bulge profiles are not well-fitted by the classic de Vaucouleurs profile, and that exponential or R 1/2 fits are preferred. Bulge-to-disk ratio correlates only weakly with Hubble type. Many of the galaxies show central reddening of their J-K colours, which we interpret as due to nuclear starbursts or dusty AGN. We define a new method for measuring the strength of bars, which we call Equivalent Angle. We stress that this is better than the traditional bar-interbar contrast, as it is not subject to seeing and resolution effects. Bars are found in 40 of the 45 galaxies, 9 of which had been previously classified as unbarred. Bar strengths are found not to correlate with disk surface brightness or the presence of near neighbours, but a tendency is found for the most strongly barred galaxies to lie within a restricted, intermediate range of bulge-to-disk ratio. Bar light profiles are found to be either flat or exponentially decreasing along their long axes, with profile type not correlating strongly with Hubble type. Bar short axis profiles are significantly asymmetric, with the steeper profile being generally on the leading edge, assuming trailing arms. In the K-band we find bars with higher axial ratios than have been found previously in optical studies.
The Frequency of Barred Spiral Galaxies in the Near-Infrared
The Astronomical Journal, 2000
We have determined the fraction of barred galaxies in the H-band for a statistically well-defined sample of 186 spirals drawn from the Ohio State University Bright Spiral Galaxy survey. We find 56% of our sample to be strongly barred at H, while another 16% is weakly barred. Only 27% of our sample is unbarred in the near-infrared. The RC3 and the Carnegie Atlas of Galaxies both classify only about 30% of our sample as strongly barred. Thus strong bars are nearly twice as prevalent in the near-infrared as in the optical.
Near‐Infrared and Optical Morphology of Spiral Galaxies
The Astrophysical Journal Supplement Series, 2002
We announce the initial release of data from the Ohio State University Bright Spiral Galaxy Survey, a BV RJHK imaging survey of a well-defined sample of 205 bright, nearby spiral galaxies. We present H-band morphological classification on the Hubble sequence for the OSU Survey sample. We compare the H-band classification to B-band classification from our own images and from standard galaxy catalogs. Our B-band classifications match well with those of the standard catalogs. On average, galaxies with optical classifications -2from Sa through Scd appear about one T-type earlier in the H-band than in the B-band, but with large scatter. This result does not support recent claims made in the literature that the optical and near-IR morphologies of spiral galaxies are uncorrelated. We present detailed descriptions of the H-band morphologies of our entire sample, as well as B-and H-band images for a set of 17 galaxies chosen as type examples, and BRH color-composite images of six galaxies chosen to demonstrate the range in morphological variation as a function of wavelength. Data from the survey are accessible at A common property, and, therefore, a common weakness of all these schemes has been the nearly exclusive use of B-band plate material for galaxy classification (although see Zwicky 1955 and Schweizer 1976 for early work on multiwavelength morphology). This constrains existing classification schemes in two major ways. First, as classification has been done primarily in the B-band, it is very sensitive to the distribution of blue stars and dust. This is particularly unfortunate for the study of late-type galaxies, as the distribution of the young, blue stars and the dust can be very different from the distribution of the total baryonic mass. Second, although well-exposed plates, taken under good seeing conditions, can offer excellent spatial resolution, plates are poor photometric detectors, and have a very limited dynamic range. Thus, for instance, it is possible to miss features such as nuclear bars in classification plates that are deeply exposed in order to reveal the structure of spiral arms in the outer disk (see for a discussion of this effect).
The structure of spiral galaxies -- II. Near-infrared properties of spiral arms
Monthly Notices of the Royal Astronomical Society, 1998
We have imaged a sample of 45 face-on spiral galaxies in the K-band, to determine the morphology of the old stellar population, which dominates the mass in the disk. The K-band images of the spiral galaxies have been used to calculate different characteristics of the underlying density perturbation such as arm strengths, profiles and cross-sections, and spiral pitch angles. Contrary to expectations, no correlation was found between arm pitch angle and Hubble type, and combined with previous results this leads us to conclude that the morphology of the old stellar population bears little resemblance to the optical morphology used to classify galaxies. The arm properties of our galaxies seem inconsistent with predictions from the simplest density wave theories, and some observations, such as variations in pitch angle within galaxies, seem hard to reconcile even with more complex modal theories. Bars have no detectable effect on arm strengths for the present sample. We have also obtained B-band images of three of the galaxies. For these galaxies we have measured arm cross-sections and strengths, to investigate the effects of disk density perturbations on star formation in spiral disks. We find that B-band arms lead K-band arms and are narrower than K-band arms, apparently supporting predictions made by the large scale shock scenario, although the effects of dust on B-band images may contribute towards these results.
The Astronomical Journal, 2001
We study the characteristics of central star-forming regions of early-type spiral galaxies by optical spectroscopic observations. The sample consists of 13 galaxies which have ratios of far-infrared (FIR) to optical B-band luminosity, larger than the average of this type, [0.5. Strong line emissions log (L FIR /L B ), are detected around the nucleus, and the line ratios of most regions are H II region-like, except for a few shocked regions. There is no low-ionization nuclear emission-line region (LINER). The [N II] and [S II] lines are somewhat enhanced, compared to the disk H II regions, but the enhancements cannot be attributed to hidden active galactic nuclei (AGNs) and the shock excitation. The median extinction derived from the Ha/Hb intensity ratio is 1.0 mag in and the median SFR of our sample galaxies, corrected A V , for extinction, is estimated to be 2 yr~1. Both values are comparable to those of late-type spiral M _ galaxies. We Ðnd a correlation that the radii of the central star-forming regions tend to become larger with the turn-over radii of the rotation curves.
Ionised gas abundances in barred spiral galaxies
Astronomy & Astrophysics, 2012
Aims. This is the third paper of a series devoted to study the properties of bars from long slit spectroscopy to understand their formation, evolution and their influence on the evolution of disk galaxies. In this work we aim to determine the gas metallicity distribution of a sample of 20 barred early-type galaxies. We compare the nebular and stellar metallicity distributions to conclude about the origin of the warm gas. Methods. Long-slit spectroscopy along the bar was obtained and metallicities derived using different calibrations. We compare the results of nebular emission metallicities using different semi-empirical methods. We carry out AGN diagnostic diagrams along the radius to determine the radius of influence of the AGN and the nuclei nature of the studied galaxies. We then derive the gas metallicities along the bars and compare the results to the distribution of stellar metallicities in the same regions.
Stellar kinematic data for the central region of spiral galaxies. II
Astronomy and Astrophysics Supplement Series, 1999
We present a second dataset of absorption spectroscopy on the inner region of spiral galaxies. We have determined the central velocity dispersion for 42 Sa-Sc objects and, for 32 of them, stellar rotation curves and velocity-dispersion profiles. Some of these profiles are limited to the bulge, some others do reach a region dominated by the luminosity of the disk. These data are intended to provide basic material for the study of the mass distribution and dynamical status in the central regions of spiral galaxies. Although no elaborate bulge-and-disk photometric decomposition is performed, we estimate the effects of limited resolution and contamination by disk light on the central velocity dispersion of the bulge. All the material presented in this paper, in particular the spectra, is available on-line.
Monthly Notices of the Royal Astronomical Society, 2009
We analyse V and H-band surface photometry of a sample of 18 Sb-Sd galaxies. Combining high resolution HST images with ground-based NIR observations, we extract photometric profiles, which cover the whole disk and provide the highest possible resolution. This is the first photometric study of late-type spirals for which the stellar kinematics have been measured. For 10 out of the 18 galaxies, HST data in both F160W (H) and F606W (V ) are available, and, for those, we present colour maps and radial colour profiles at the resolution of the Hubble Space Telescope.