J/A+A/611/A38 Hints for a bar in M31 kinematics and morphology (Opitsch+, 2018)
Evidence for non-axisymmetry in M 31 from wide-field kinematics of stars
and gas.
Opitsch M., Fabricius M.H., Saglia R.P., Bender R., Blana M., Gerhard O.
<Astron. Astrophys., 611, A38 (2018)>
=2018A&A...611A..38O 2018A&A...611A..38O (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Populations, stellar ; Radial velocities ;
Velocity dispersion ; Spectroscopy
Keywords: galaxies: bulges - galaxies: structure -
galaxies: kinematics and dynamics - Local Group -
techniques: spectroscopic
Abstract:
As the nearest large spiral galaxy, M 31 provides a unique opportunity
to study the structure and evolutionary history of this galaxy type in
great detail. Among the many observing programs aimed at M 31 are
microlensing studies, which require good three-dimensional models of
the stellar mass distribution. Possible non-axisymmetric structures
like a bar need to be taken into account. Due to M 31's high
inclination, the bar is difficult to detect in photometry alone.
Therefore, detailed kinematic measurements are needed to constrain the
possible existence and position of a bar in M 31.
We obtained ~=220 separate fields with the optical integral-field unit
spectrograph VIRUS-W, covering the whole bulge region of M 31 and
parts of the disk. We derived stellar line-of-sight velocity
distributions from the stellar absorption lines, as well as velocity
distributions and line fluxes of the emission lines Hβ, [OIII]
and [NI]. Our data supersede any previous study in terms of spatial
coverage and spectral resolution.
We find several features that are indicative of a bar in the
kinematics of the stars, we see intermediate plateaus in the velocity
and the velocity dispersion, and correlation between the higher moment
h3 and the velocity. The gas kinematics is highly irregular, but is
consistent with non-triaxial streaming motions caused by a bar. The
morphology of the gas shows a spiral pattern, with seemingly lower
inclination than the stellar disk. We also look at the ionization
mechanisms of the gas, which happens mostly through shocks and not
through starbursts.
Description:
The individual spectra from the fiber based IFU were binned following
a Voronoi binning scheme to increase the SN. The first table lists the
on-sky positions of the individual fiber spectra and the bin number
that they got added to. The second table contains stellar and nebular
emission line kinematic data and fluxes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb4.dat 47 45328 On-sky positions of the individual fiber spectra
tableb5.dat 184 6473 Stellar and nebular emission line kinematic
data and fluxes (tables B5-B7 of the paper)
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See also:
J/MNRAS/459/2262 : Maps of dust distribution in M31 bulge (Dong+, 2016)
J/MNRAS/473/4130 : M31 center emission-line point-like sources (Martin+, 2018)
Byte-by-byte Description of file: tableb4.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Bin [0/6472] Number of the Voronoi bin
6- 7 I2 h RAh Right Ascension (J2000)
9- 10 I2 min RAm Right Ascension (J2000)
12- 16 F5.2 s RAs Right Ascension (J2000)
18 A1 --- DE- Declination sign (J2000)
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 29 F5.2 arcsec DEs Declination (J2000)
31- 38 F8.2 arcsec xpos Coordinate, centered on nucleus, +x to West
40- 47 F8.2 arcsec ypos Coordinate, centered on nucleus, +y to North
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Byte-by-byte Description of file: tableb5.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Bin [0/6472] Number of the Voronoi bin
6- 12 F7.2 km/s vstar Mean stellar radial velocity
14- 17 F4.2 km/s e_vstar Error of mean stellar radial velocity
19- 24 F6.2 km/s sigmastar Stellar velocity dispersion
26- 30 F5.2 km/s e_sigmastar Error of stellar velocity dispersion
32- 36 F5.2 --- h3star Third Gauss-Hermite moment
38- 41 F4.2 --- e_h3star Error in third Gauss-Hermite moment
43- 47 F5.2 --- h4star Fourth Gauss-Hermite moment
49- 52 F4.2 --- e_h4star Error in fourth Third Gauss-Hermite
moment
54- 60 F7.2 km/s v[OIII] ?=999 [OIII] line velocity
62- 68 F7.2 km/s e_v[OIII] ?=999 Error in [OIII] line velocity
70- 75 F6.2 km/s sigma[OIII] ?=999 [OIII] line velocity dispersion
77- 83 F7.2 km/s e_sigma[OIII] ?=999 Error in [OIII] velocity
dispersion
85- 91 F7.2 km/s v[OIII]2 ?=999 2nd component [OIII] line
velocity
93- 98 F6.2 km/s e_v[OIII]2 ?=999 Error in 2nd component [OIII]
velocity
100-105 F6.2 km/s sigma[OIII]2 ?=999 2nd component [OIII] line
velocity dispersion
107-112 F6.2 km/s e_sigma[OIII]2 ?=999 Error in 2nd component [OIII]
dispersion
114-118 F5.1 10-18W/m2 FHb ?=999 Flux in Hβ line (1)
120-124 F5.1 10-18W/m2 e_FHb ?=999 Error of Hβ flux (1)
126-130 F5.1 10-18W/m2 F[OIII] ?=999 Flux in [OIII] line (1)
132-136 F5.1 10-18W/m2 e_F[OIII] ?=999 Error of [OIII] flux (1)
138-142 F5.1 10-18W/m2 F[NII] ?=999 Flux in [NII] line (1)
144-148 F5.1 10-18W/m2 e_F[NII] ?=999 Error of [NII] flux (1)
150-154 F5.1 10-18W/m2 FHb2 ?=999 Flux in 2nd component
Hβ line (1)
156-160 F5.1 10-18W/m2 e_FHb2 ?=999 Error of 2nd component
Hβ flux (1)
162-166 F5.1 10-18W/m2 F[OIII]2 ?=999 Flux in 2nd component
[OIII] line (1)
168-172 F5.1 10-18W/m2 e_F[OIII]2 ?=999 Error of 2nd component
[OIII] flux (1)
174-178 F5.1 10-18W/m2 F[NII]2 ?=999 Flux in 2nd component
[NII] line (1)
180-184 F5.1 10-18W/m2 e_F[NII]2 ?=999 Error of 2nd component
[NII] flux (1)
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Note (1): in 10-15erg/s/cm2.
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Acknowledgements:
Michael Opitsch, mxhf(at)mpe.mpg.de
(End) Patricia Vannier [CDS] 31-Jul-2018