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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 (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:
FileName Lrecl Records Explanations
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)
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
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: tableb5.dat
Bytes Format Units Label Explanations
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)
Note (1): in 10-15erg/s/cm2.
Acknowledgements: Michael Opitsch, mxhf(at)
(End) Patricia Vannier [CDS] 31-Jul-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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