M 82's stellar bar

Greve, A.; Wills, K. A.; Neininger, N.; Pedlar, A.

doi:10.1051/0004-6361:20011723

Cited by 20 publications

(35 citation statements)

References 25 publications

(55 reference statements)

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“…This interpretation is not ironclad, and needs to be tested by directly measuring the size of the stellar disk. Indeed, a caveat when interpreting velocity measurements in M82 is that the dynamics in the central regions of the galaxy are dominated by a bar (Wills et al 2000), which accounts for a significant fraction of the total galaxy mass, and so is a dynamically significant component (e.g., Greve et al 2002). Moreover, the velocity field defined by the [S iii] 9069 Å line challenges the presence of Keplerian rotation outside of the region affected by the bar (McKeith et al 1993).…”

Section: Introductionmentioning

confidence: 99%

And the Rest: The Stellar Archeological Record of M82 Outside the Central Starburst

Davidge

2008

The Astronomical Journal

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Deep images obtained with MegaCam and WIRCam on the Canada-France-Hawaii Telescope are used to probe the stellar content outside of the central star-forming regions of M82. Stars evolving on the asymptotic giant branch (AGB) are traced along the major axis out to projected distances of 12 kpc, which corresponds to 13 disk scale lengths. The numbers of red supergiants (RSGs) and AGB stars normalized to local surface brightness (the "specific frequency" or SF) is constant when R GC > 4 kpc, indicating that RSGs and AGB stars are well mixed throughout the disk. Moreover, the SF of bright AGB stars in the outer disks of M82 and the Sc galaxy NGC 2403 are identical, suggesting that the specific star-formation rates (SFRs) in these galaxies during intermediate epochs were similar. This similarity in stellar content, coupled with the presence of an extended stellar disk, is consistent with M82 having been a late-type disk galaxy prior to interacting with M81. Still, there is a paucity of RSGs in the outer disk of M82 when compared with NGC 2403, indicating that the SFR in the outer regions of M82 during the past ∼0.1 Gyr has declined dramatically with respect to that in isolated late-type galaxies. The stellar content of the M82 disk plane is also investigated. A mixture of bright main-sequence stars, RSGs, and AGB stars is detected out to minor-axis distances of 7 kpc. These stars, which span a range of ages, are concentrated along the outflow. The brightest extraplanar AGB stars define a system with an exponential scale height of 1.8 ± 0.2 kpc, as measured along the minor axis. It is suggested that the young-and intermediate-aged stars in the extraplanar regions formed in structures similar to M82 South, and that these were subsequently disrupted by the tidal action of M82.

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Section: Introductionmentioning

confidence: 99%

And the Rest: The Stellar Archeological Record of M82 Outside the Central Starburst

Davidge

2008

The Astronomical Journal

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“…It is also possible that any young and intermediate-age stars in the outer regions of M82 may not have formed in situ, as interactions with M81 and NGC 3077 may have created tidal arms that moved stars out of the plane of the disk. Finally, M82 has a central bar (Telesco et al 1991) that contains 20%-40% of the total galaxy mass (Greve et al 2002), and the disruption of this structure could scatter young stars away from the center of the galaxy (see, e.g., Mayer et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Deep Near‐Infrared Imaging of a Field in the Outer Disk of M82 with the Altair Adaptive Optics System on Gemini‐North

Davidge¹,

Stoesz²,

Rigaut³

et al. 2004

PUBL ASTRON SOC PAC

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ABSTRACT.Deep H and images recorded with the Altair adaptive optics system and Near-Infrared Imager K on Gemini-North are used to probe the red stellar content in a field with a projected distance of 1 kpc above the disk plane of the starburst galaxy M82. The data have an angular resolution of 0Љ .08 FWHM, and individual asymptotic giant branch (AGB) and red giant branch (RGB) stars are resolved. The AGB extends to at least 1.7 mag in K above the RGB tip, which occurs at . The relative numbers of bright AGB stars and RGB K p 21.7 stars are consistent with stellar evolution models, and one of the brightest AGB stars has an HϪK color and K brightness that is consistent with it being a C star. The brightnesses of the AGB stars suggest that they formed during intermediate epochs, possibly after the last major interaction with M81. Therefore, star formation in M82 during intermediate epochs may not have been restricted to the plane of the disk.

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“…We combined these data with radial velocities that we published earlier (McKeith et al 1993;Greve et al 2002;abbreviated McK93 and GWNP). We used in addition other radial velocity data at near-IR and visible wavelengths (Westmoquette et al 2009;Whitmore et al 1984) and data of stellar clusters (Konstantopoulos et al 2009) and planetary nebulae (Johnson et al 2009).…”

Section: The Earlier and Unpublished Optical Observationsmentioning

confidence: 99%

“…H i, CO, and (near-)IR velocity observations have revealed the bar's x 1 -orbits, between ∼±30 , and the inner, perpendicular x 2 -orbits, between ∼±10 (e.g. Wills et al 2000;Achtermann & Lacy 1995;Greve et al 2002). Mayya et al (2005;see also Ichikawa et al 1995) used IR images to derive a stellar disk of ∼50 scale length and two trailing spiral arms starting at right angles to the eastern and western extremes of the bar.…”

Section: Introductionmentioning

confidence: 99%

“…The encounter has left long H i and CO tidal arms (Yun et al 1993(Yun et al , 1994Brouillet et al 1991;Taylor et al 2001;Walter et al 2002). It reshuffled the stars and the gas of the original M 82-galaxy, formed a bar (Telesco et al 1991;Larkin et al 1994;Wills et al 2000;Greve et al 2002), and produced successive and strong starbursts in the center region (e.g. Rieke et al 1980;Förster Schreiber et al 2001;de Grijs et al 2001;Smith et al 2007).…”

Section: Introductionmentioning

confidence: 99%

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The apparent “reversed” motion of gas and stars in M 82

Greve

2011

A&A

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We summarize earlier and unpublished long-slit spectroscopic measurements of radial velocities of ionized gas and stars along and parallel to M 82's major axis to a radial distance of ∼±2.5 kpc (∼±140 ) from the center. In the position-velocity diagram, these measurements indicate a velocity reversal of ∼100 km s −1 of gas and/or stars at ∼±1.0 kpc (∼±50−70 ) on either side of the center, outside the bar. Although seen in earlier observations, and perhaps neglected because they were assumed to be only an effect of heavy local extinction, the positional symmetry of the velocity reversal with respect to the center of M 82, as well as the absence of the reversal in the motion of stars seen in the near-IR Ca ii absorption lines, points to another origin. M 82's two-armed spiral, as outlined by Mayya et al. (2005, ApJ, 628, L33), may explain a part of the velocity reversal, although this interpretation leaves inconsistencies so that other explanations must also be investigated. A simple, conclusive explanation of the velocity reversal has not yet been found. While restricted observationally in radial distance to ∼120 (2 kpc), the near-IR stellar Ca ii absorption lines, which do not show the velocity reversal, indicate a flat radial velocity curve of the stellar disk that remained after the encounter with M 81.

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M 82's stellar bar

Cited by 20 publications

References 25 publications

And the Rest: The Stellar Archeological Record of M82 Outside the Central Starburst

And the Rest: The Stellar Archeological Record of M82 Outside the Central Starburst

Deep Near‐Infrared Imaging of a Field in the Outer Disk of M82 with the Altair Adaptive Optics System on Gemini‐North

The apparent “reversed” motion of gas and stars in M 82

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