An Arc of Young Stars in the Halo of M82

Davidge, T. J.

doi:10.1086/588551

Cited by 11 publications

(18 citation statements)

References 34 publications

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“…An interesting feature is the pair of arcs that can be seen above and below the disk of M82. These arcs were also noted by Okamoto et al (2015), and the southern arc was also discussed in detail in Davidge (2008) and Sun et al (2005). Davidge (2008) estimates that the stellar mass of the arc is between 3·10 5 M and 2·10 6 M , with an age of ∼ 5·10 7 years, consistent with the typical interaction timescale in the triplet.…”

Section: Star Formation In and Around The M81 Tripletsupporting

confidence: 67%

“…These arcs were also noted by Okamoto et al (2015), and the southern arc was also discussed in detail in Davidge (2008) and Sun et al (2005). Davidge (2008) estimates that the stellar mass of the arc is between 3·10 5 M and 2·10 6 M , with an age of ∼ 5·10 7 years, consistent with the typical interaction timescale in the triplet. Davidge (2008) speculates that the arc could have formed due to triggered star formation as a result of the M82 outflows and notes that it coincides with a similar arc seen in GALEX UV-data (Hoopes et al 2005).…”

Section: Star Formation In and Around The M81 Tripletsupporting

confidence: 67%

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A High-resolution Mosaic of the Neutral Hydrogen in the M81 Triplet

Blok

Walter

Ferguson

et al. 2018

ApJ

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We present a 3 • ×3 • , 105-pointing, high-resolution neutral hydrogen (H i) mosaic of the M81 galaxy triplet, (including the main galaxies M81, M82 and NGC 3077, as well as dwarf galaxy NGC 2976) obtained with the Very Large Array (VLA) C and D arrays. This H i synthesis mosaic uniformly covers the entire area and velocity range of the triplet. The observations have a resolution of ∼ 20 or ∼ 420 pc. The data reveal many small-scale anomalous velocity features highlighting the complexity of the interacting M81 triplet. We compare our data with Green Bank Telescope (GBT) observations of the same area. This comparison provides evidence for the presence of a substantial reservoir of low-column density gas in the northern part of the triplet, probably associated with M82. Such a reservoir is not found in the southern part. We report a number of newly discovered kpc-sized low-mass H i clouds with H i masses of a few times 10 6 M . A detailed analysis of their velocity widths show that their dynamical masses are much larger than their baryonic masses, which could indicate the presence of dark matter if the clouds are rotationally supported. However, due to their spatial and kinematical association with H i tidal features, it is more likely that the velocity widths indicate tidal effects or streaming motions. We do not find any clouds that are not associated with tidal features down to an H i mass limit of a few times 10 4 M . We compare the H i column densities with resolved stellar density maps and find a star formation threshold around 3 − 6 · 10 20 cm −2 . We investigate the widths of the H i velocity profiles in the triplet and find that extreme velocity dispersions can be explained by a superposition of multiple components along the line of sight near M81 as well as winds or outflows around M82. The velocity dispersions found are high enough that these processes could explain the linewidths of Damped-Lyman-α absorbers observed at high redshift.

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Section: Star Formation In and Around The M81 Tripletsupporting

confidence: 67%

Section: Star Formation In and Around The M81 Tripletsupporting

confidence: 67%

A High-resolution Mosaic of the Neutral Hydrogen in the M81 Triplet

Blok

Walter

Ferguson

et al. 2018

ApJ

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“…Still, a concentration of AGB stars can be traced out to D Z = 7 kpc in Figures 11 and 12, while objects with colors and brightnesses that are consistent with them being RSGs are also seen out to D Z = 7 kpc in Figure 11. The presence of possible RSGs at this D Z is perhaps not surprising given that RSGs are present in M82 South (Davidge 2008).…”

Section: An Overview Of the Cmdsmentioning

confidence: 85%

“…Some of this gas appears to have cooled sufficiently to allow stars to form, as stars with ages ∼50 Myr are seen in M82 South (Davidge 2008). While M82 South appears to be the most obvious extraplanar stellar structure associated with M82 (Section 4.2), there may be other, albeit less pronounced, collections of young extraplanar stars.…”

Section: Bright Extraplanar Stars and Clustersmentioning

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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“…A number of small clumps are also seen as they follow HI blobs around these systems. The stellar concentration in the NW-arm was identified by Davidge (2008b) and was suggested to be part of the M81 arm by Barker et al (2009). We confirm that it is connected to the stellar concentration on the north arm.…”

Section: The Spatial Distributions Of Youngmentioning

confidence: 96%

A Hyper Suprime-Cam View of the Interacting Galaxies of the M81 Group

Okamoto

Arimoto

Ferguson

et al. 2015

ApJ

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We present the first results of a wide-field mapping survey of the M81 group conducted with Hyper Suprime-Cam on the Subaru Telescope. Our deep photometry reaches ∼ 2 magnitudes below the tip of the red giant branch (RGB) and reveals the spatial distribution of both old and young stars over an area of ∼ 100 × 115 kpc at the distance of M81. The young stars (∼ 30 − 160 Myr old) closely follow the neutral hydrogen distribution and can be found in a stellar stream between M81 and NGC 3077 and in numerous outlying stellar associations, including the known concentrations of Arp's Loop, Holmberg IX, an arc in the halo of M82, BK3N, and the Garland. Many of these groupings do not have counterparts in the RGB maps, suggesting they may be genuinely young systems. Our survey also reveals for the first time the very extended (≥ 2 × R 25 ) halos of RGB stars around M81, M82 and NGC 3077, as well as faint tidal streams that link these systems. The halos of M82 and NGC 3077 exhibit highly disturbed morphologies, presumably a consequence of the recent gravitational encounter and their ongoing disruption. While the halos of M81, NGC 3077 and the inner halo of M82 have the similar (g − i) 0 colors, the outer halo of M82 is significantly bluer indicating it is more metal-poor. Remarkably, our deep panoramic view of the M81 group demonstrates that the complexity long-known to be present in HI is equally matched in the low surface brightness stellar component.

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An Arc of Young Stars in the Halo of M82

Cited by 11 publications

References 34 publications

A High-resolution Mosaic of the Neutral Hydrogen in the M81 Triplet

A High-resolution Mosaic of the Neutral Hydrogen in the M81 Triplet

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

A Hyper Suprime-Cam View of the Interacting Galaxies of the M81 Group

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