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Optical picture of IC 5249 taken from the second generation red Digital Sky Survey. The frame measures 4.4 × 3.6 arcmin and south is to the left.
Source publication
We present spectroscopic observations of the stellar motions in the disk of the superthin edge-on spiral galaxy IC 5249 and re-analyse synthesis observations of the HI. We find that the HI rotation curve rises initially to about 90-100 km/s, but contrary to the conclusion of Abe et al. (1999) flattens well before the edge of the optical disk. Over...
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Context 1
... the sky is of order 5 to 10 in the ratio of the scale parameters and consequently also in observed isophotes, there remains a class of so-called "superthin" galaxies, in which the axis ratio on the sky surveys ap- pears much larger. A beautiful example of such a system is IC 5249, which has an axis ratio of about 20 on the Digital Sky Survey (see Fig. 1). If indeed the ratio of the scalelength and the scaleheight would be that large, the axis ratio of the stellar velocity ellipsoid can still be of the order 0.45 according to the equation referred to above, but it would seriously constrain the models for secular evolution that would have to be much more efficient in the radial than in ...
Context 2
... 5249 from a long slit spectrum along the major axis. The top panel shows the number of counts along the slit (south is on the left side); the horizontal arrows show the ranges along the slit that are referred to in the text as (from left to right) B, A and C. Note that two stars are on the slit of which the one on the right can be identified in Fig. 1. The middle panel shows the observed stellar radial velocity. The horizontal bars are the ranges along the slit over which data have been added to decrease the signal to noise. The lower panel shows the velocity dispersions. Before adding data over ranges along the slit these were shifted according to the run of radial velocity in the ...
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Citations
... Karachentsev et al. (2016) discovered that flat galaxies with very thin disks have fewer satellite companions than regular spiral galaxies. Moreover, spectroscopic studies of small samples of STGs (Goad & Roberts 1981;van der Kruit et al. 2001;Matthews & Uson 2008;O'Brien et al. 2010;Banerjee & Bapat 2017;Bizyaev et al. 2017;Kurapati et al. 2018) indicate that the galaxies grew up and evolved in rather unperturbed cosmological environments (B17) and hence allow us to study the galactic disk formation disentangled from the consequent dynamical evolution. ...
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... Besides UGC7321, only two other superthin galaxies have been studied in detail: IC5249 (van der Kruit et al. 2001;Banerjee & Bapat 2017) and IC2233 (Banerjee & Bapat 2017). In this paper, we study FGC 1540, a prototypical superthin galaxy in detail. ...
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... FGC1540 was found to be consistent with a model consisting of a superposition of a thin disc and a thick disc, with each of the discs having an exponential radial profile and a sech 2 vertical profile. The surface brightness profiles were converted to mass density profiles assuming a mass-to-light ratio γ * of 0.35, the average γ * value as calculated for a sample of superthin galaxies (van der Kruit et al. 2001;Banerjee & Bapat 2017). We find that the thin disc has a central density of 8.16 M pc −2 , has a scale length of 0.54 kpc and a scale height of 0.152 kpc; the thick disc has a central density of 3.24 M pc −2 , has a scale length of 1.85 kpc and a scale height of 0.43 kpc. ...
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... Another good example of a superthin galaxy is IC 5249 (Byun, 1998;Abe et al., 1999;van der Kruit et al., 2001). This also is a faint surface brightness galaxy with presumably a small fraction of the mass in the luminous disk. ...
In this review I concentrate on three areas related to structure of disks in spiral galaxies. First I will review the work
on structure, kinematics, and dynamics of stellar disks. Next I will review the progress in the area of flaring of Hi layers. These subjects are relevant for the presence of dark matter and lead to the conclusion that disks are in general
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... ESO109-G021 is a superthin Sd galaxy with B-band stellar scalelength-to-scaleheight ratio of 11 (van der Kruit et al., 2001). The rotation curve was initially found to be in solid body rotation by Abe et al. (1999), however van der Kruit et al. (2001) pointed out such a rotation curve was inconsistent with the double-horned HI spectrum (seeFig. 2b). ...
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... and to the value (20 kms −1 ) estimated analytically for the superthin galaxy IC 5249 by van der Kruit et al. (2001). We assume the central value of velocity dispersion to fall off exponentially with radius with a scale length of 2 R d (which is equal to 4.2 kpc for UGC 7321) as is seen in the Galaxy (Lewis & Freeman 1989). ...
We model the shape and density profile of the dark matter halo of the low surface brightness, superthin galaxy UGC 7321, using the observed rotation curve and the H i scale height data as simultaneous constraints. We treat the galaxy as a gravitationally coupled system of stars and gas, responding to the gravitational potential of the dark matter halo. An isothermal halo of spherical shape with a core density in the range of and a core radius between 2.5 and 2.9 kpc, gives the best fit to the observations for a range of realistic gas parameters assumed. We find that the best-fit core radius is only slightly higher than the stellar disc scale length (2.1 kpc), unlike the case of the high surface brightness galaxies where the halo core radius is typically 3–4 times the disc scale length of the stars. Thus our model shows that the dark matter halo dominates the dynamics of the low surface brightness, superthin galaxy UGC 7321 at all radii, including the inner parts of the galaxy.
... Until recently, only few edge-on LSB galaxies have been explored in detail (e.g. UGC 7321 Matthews (2000) and IC 5249 van der Kruit et al. (2001)). We conducted a study of a small uniform sample of LSB and HSB galaxies observed with the same instrument to compare their structural parameters. ...
We present surface photometry results for a sample of 11 edge-on galaxies observed with the 6 m telescope at the Special Astrophysical Observatory, Russia. The photometric scale length, scale height, and central surface brightness of the stellar disks of our sample galaxies are estimated. We show that four galaxies in our sample, which are visually classified as objects of the lowest surface brightness class in the Revised Flat Galaxy Catalog, have bona fide low surface brightness (LSB) disks. We find from a comparison of photometric scales that the stellar disks of LSB galaxies are thinner than those of high surface brightness (HSB) galaxies. There is a clear correlation between the central surface brightness of the stellar disk and its vertical-to-radial scale ratio. The masses of spherical subsystems (dark halo + bulge) and the dark halo masses are obtained for the sample galaxies based on the thickness of their stellar disks. The LSB galaxies tend to harbor more massive spherical subsystems than the HSB objects, whereas no systematic difference in the dark halo masses is found between LSB and HSB galaxies. At the same time, the inferred mass-to-luminosity ratio for the LSB disks appears to be systematically higher than for HSB disks.
... Most investigations begin with the assumption that a disk's mass-to-light ratio is constant with radius (e.g., Kent 1986; Palunas & Williams 2000; Sofue et al. 2003), but evidence in support of this hypothesis is limited. In fact, independent estimates of disk mass exist for only a handful of spirals (e.g., Bottema 1993; Bottema, van der Kruit, & Freeman 1987; van der Kruit et al. 2001; Gerssen, Kuijken, & Merrifield 1997), and in these systems, the data are restricted to the galaxies' inner ∼ 2 scale lengths. Thus, while the information to date is consistent with the constant mass-to-light ratio hypothesis, the applicability of these studies to the dark-matter-dominated outer regions of spirals is limited. ...
We report the results of a photometric and spectroscopic survey for planetary nebulae (PNe) in the Local Group spiral galaxy M33. We use our sample of 152 PNe to derive an [O III] planetary nebula luminosity function (PNLF) distance of (m-M)_0 = 24.86^+0.07-0.11 (0.94^+0.03-0.05 Mpc). Although this value is ~ 15% larger than the galaxy's Cepheid distance, the discrepancy likely arises from differing assumptions about the system's internal extinction. Our photometry (which extends >3 mag down the PNLF), also reveals that the faint-end of M33's PN luminosity function is non-monotonic, with an inflection point ~2 mag below the PNLF cutoff. We argue that this feature is due to the galaxy's large population of high core-mass planetaries, and that its amplitude may eventually be useful as a diagnostic for studies of stellar populations. Fiber-coupled spectroscopy of 140 of the PN candidates confirms that M33's PN population rotates along with the old disk, with a small asymmetric drift of \~ 10km/s. Remarkably, the population's line-of-sight velocity dispersion varies little over ~4 optical disk scale lengths, with sigma_{rad}~20km/s. We show that this is due to a combination of factors, including a decline in the radial component of the velocity ellipsoid at small galactocentric radii, and a gradient in the ratio of the vertical to radial velocity dispersion. We use our data to show that the mass scale length of M33's disk is ~2.3 times larger than that of the system's IR luminosity and that the disk's V-band mass-to-light ratio changes from M/L_V ~0.3 in the galaxy's inner regions to M/L_V ~2.0 at ~9 kpc. Models in which the dark matter is distributed in the plane of the galaxy are excluded by our data. (abridged)
... We now know (KK04) that there is a sharp transition between Sb and Sc; Sb-and earlier-type galaxies mostly contain classical bulges; Sbc galaxies contain pseudobulges more often than bulges, and Sc-and later-type galaxies appear never to have classical bulges. This implies that a majority of field galaxies -not just a few, remarkably flat, edge-on, bulgeless disks (Matthews, Gallagher, & van Driel 1999;Freeman 2000;van der Kruit et al. 2001) -show no signs of major merger violence. The challenge for hierarchical clustering is correspondingly increased. ...
We review internal secular evolution in galaxy disks -- the fundamental process by which isolated disks evolve. We concentrate on the buildup of dense central features that look like classical, merger-built bulges but that were made slowly out of disk gas. We call these pseudobulges. As an existence proof, we review how bars rearrange disk gas into outer rings, inner rings, and gas dumped into the center. In simulations, this gas reaches high densities, and in the observations, many SB and oval galaxies show central concentrations of gas. Associated star formation rates imply plausible pseudobulge growth times of a few billion years. If secular processes built dense centers that masquerade as bulges, can we distinguish them from merger-built bulges? Observations show that pseudobulges retain a memory of their disky origin. They have one or more characteristics of disks: (1) flatter shapes than those of classical bulges, (2) larger ratios of ordered to random velocities, (3) smaller velocity dispersions, (4) nuclear bars or spiral structure, (5) boxy structure when seen edge-on, (6) nearly exponential brightness profiles, and (7) starbursts. These features occur preferentially in barred and oval galaxies in which secular evolution should be rapid. So the cleanest examples of pseudobulges are recognizable. Thus observations and theory contribute to a new picture of galaxy evolution that complements hierarchical clustering and merging. However, an important problem with cold dark matter galaxy formation gets more acute. How can hierarchical clustering produce so many pure disk galaxies with no evidence for merger-built bulges?
... It is also not possible to say much about the thickness of the other nuclear disks, due to their inclination (not as edge-on as NGC 5308). Whether this nuclear disk resembles the disks from the group of " superthin " galaxies, like UGC 7321 or IC 5249 (Matthews et al. 1999; Matthews 2000; van der Kruit et al. 2001), is an open question. The sizes of the nuclear disk in NGC 5308 and known " super-thin " disks are quite different as well as the surrounding environment (stellar bulges and dark matter halos respectively). ...
We present observations of four nearby early-type galaxies with
previously known nuclear stellar disks using two instruments on-board
the Hubble Space Telescope. We observed NGC 4128, NGC 4612, and NGC 5308
with the Wide Field Planetary Camera 2, and the same three galaxies,
plus NGC 4570, with the Space Telescope Imaging Spectrograph. We have
detected a red nucleus in NGC 4128, a blue nucleus in NGC 4621, and a
blue disk in NGC 5308. Additionally, we have discovered a blue disk-like
feature with position angle ˜15° from the major axis in NGC
4621. In NGC 5308 there is evidence for a blue region along the minor
axis. We discovered a blue transient on the images of NGC 4128 at
position 0.14 arcsec west and 0.32 arcsec north from the nucleus. The
extracted kinematic profiles belong to two groups: fast (NGC 4570 and
NGC 5308) and kinematically disturbed rotators (NGC 4128 and NGC 4621).
We report the discovery of a kinematically decoupled core in NGC 4128.
Galaxies have mostly old (10-14 Gyr) stellar populations with large
spread in metallicities (sub- to super-solar). We discuss the possible
formation scenarios, including bar-driven secular evolution and the
influence of mergers, which can explain the observed color and kinematic
features.
Appendix A is only available in electronic form at the CDS via anonymous
ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/ cgi-bin/ qcat?J/A+A/428/877
Appendix B, Tables \ref{t:wfpc2}, \ref{t:filters},
\ref{t:stis_obs}-\ref{t:lsi} and Figs. \ref{f:isophote},
\ref{f:ngc5308_slit}-\ref{f:chi2}, \ref{f:ngc4128}-\ref{f:ngc5308} are
only available in electronic form at http://www.edpsciences.org
