J/MNRAS/446/4039 Stellar kinematics for NGC 2859 and NGC 4371 (Erwin+, 2015)
Composite bulges: the coexistence of classical bulges and discy pseudo-bulges
in S0 and spiral galaxies.
Erwin P., Saglia R.P., Fabricius M., Thomas J., Nowak N., Rusli S.,
Bender R., Vega Beltran J.C., Beckman J.E.
<Mon. Not. R. Astron. Soc., 446, 4039-4077 (2015)>
=2015MNRAS.446.4039E 2015MNRAS.446.4039E (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Radial velocities ; Velocity dispersion
Keywords: galaxies: bulges - galaxies: elliptical and lenticular, cD -
galaxies: evolution - galaxies: kinematics and dynamics -
galaxies: spiral - galaxies: structure
Abstract:
We present an analysis of nine S0-Sb galaxies which have (photometric)
bulges consisting of two distinct components. The outer component is a
flattened, kinematically cool, disc-like structure: a 'discy
pseudo-bulge'. Embedded inside is a rounder, kinematically hot
spheroidal structure: a `classical bulge'. This indicates that
pseudo-bulges and classical bulges are not mutually exclusive
phenomena: some galaxies have both. The discy pseudo-bulges almost
always consist of an exponential disc (scalelengths=125-870 pc,
mean size ∼440 pc) with one or more disc-related subcomponents:
nuclear rings, nuclear bars, and/or spiral arms. They constitute
11-59 percent of the galaxy stellar mass (mean PB/T=0.33), with
stellar masses ∼7x109-9x1010 M☉. The classical-bulge
components have Sersic indices of 0.9-2.2, effective radii of 25-430 pc
and stellar masses of 5x108-3x1010 M☉; they are usually
<10 percent of the galaxy's stellar mass (mean B/T=0.06). The
classical bulges do show rotation, but are clearly kinematically
hotter than the discy pseudo-bulges. Dynamical modelling of three
systems indicates that velocity dispersions are isotropic in the
classical bulges and equatorially biased in the discy pseudo-bulges.
In the mass-radius and mass-stellar mass density planes,
classical-bulge components follow sequences defined by ellipticals and
(larger) classical bulges. Discy pseudo-bulges also fall on this
sequence; they are more compact than large-scale discs of similar
mass. Although some classical bulges are quite compact, they are as a
class clearly distinct from nuclear star clusters in both size and
mass; in at least two galaxies they coexist with nuclear clusters.
Since almost all the galaxies in this study are barred, they probably
also host boxy/peanut-shaped bulges (vertically thickened inner parts
of bars). NGC 3368 shows isophotal evidence for such a zone just
outside its discy pseudo-bulge, making it a clear case of a galaxy
with all three types of 'bulge'.
Description:
We obtained long-slit spectroscopy of NGC 2959 with the ISIS spectrograph
of the WHT on 2000 December 13, using the blue arm with the R600B
grating. NGC 4371 was observed with an almost identical instrumental
setup as part of ING service-time observations on 2001 June 4.
Following standard MIDAS reduction of the ISIS observations,
including bias subtraction, flat-fielding and wavelength calibration
using CuAr and CuNe+CuAr lamp exposures, the extracted galaxy spectra
were analysed using the Fourier Correlation Quotient method (Bender
1990A&A...229..441B 1990A&A...229..441B; Bender, Saglia & Gerhard 1994MNRAS.269..785B 1994MNRAS.269..785B) in
order to determine the stellar kinematics.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
galaxy.dat 34 2 List of galaxy
tableb2.dat 67 79 Major-axis stellar kinematics for NGC 2859 and
NGC 4371
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See also:
J/AJ/136/773 : Structure of classical bulges and pseudobulges (Fisher+, 2008)
Byte-by-byte Description of file: galaxy.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Galaxy Name
10- 11 I2 h RAh Simbad Hour of Right Ascension (J2000)
13- 14 I2 min RAm Simbad Minute of Right Ascension (J2000)
16- 21 F6.3 s RAs Simbad Second of Right Ascension (J2000)
23 A1 --- DE- Simbad Sign of the Declination (J2000)
24- 25 I2 deg DEd Simbad Degree of Declination (J2000)
27- 28 I2 arcmin DEm Simbad Arcminute of Declination (J2000)
30- 34 F5.2 arcsec DEs Simbad Arcsecond of Declination (J2000)
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Byte-by-byte Description of file: tableb2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [NGC]
5- 8 I4 --- NGC [2859/4371] Galaxy name
10- 11 I2 deg PA [85/92] Position angle of the telescope
13- 18 F6.2 arcsec Rad [] Radius along the major axis
20- 25 F6.1 km/s RV Radial velocity
27- 30 F4.1 km/s e_RV Uncertainty in RV
32- 36 F5.1 km/s sigma Velocity dispersion
38- 41 F4.1 km/s e_sigma Uncertainty in sigma
43- 48 F6.3 --- h3 Gauss-Hermite coefficient h3
50- 54 F5.3 --- e_h3 Uncertainty in h3
56- 61 F6.3 --- h4 Gauss-Hermite coefficient h4
63- 67 F5.3 --- e_h4 Uncertainty in h4
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History:
From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 08-Nov-2017