Resolving the Stellar Outskirts of M81: Evidence for a Faint, Extended Structural Component

Barker, M. K.; Ferguson, Annette M. N.; Irwin, M. J.; Arimoto, N.; Jablonka, P.

doi:10.1088/0004-6256/138/5/1469

Cited by 54 publications

(87 citation statements)

References 96 publications

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“…However, notice that the HI emission disappears in the northern part of the loop where both optical and infrared images show significant contributions. Moreover, the analysis of CMDs obtained by Davidge (2009) and Barker et al (2009) has not detected any overdensity of Red Giants along Arp's loop and only identified a population of young stars in the confined region where the strong HI emission was observed. Thus, although the origin of part of the optical and UV emission in Arp's loop could be emitted by recent star formation episodes, most likely part of it has a Galactic origin.…”

Section: Discussionmentioning

confidence: 95%

“…These authors suggested that the old component could have been removed from the M 81 and/or M 82 disk during their mutual interaction. Further insight was recently provided by Barker et al (2009), who analyzed a wide area that included M 81 with deep Suprime-Cam observations. Their results revealed no overdensity of Red Giant stars along Arp's loop extension (which is at odds with De Mello et al's results), whereas a significant group of young Red Supergiants and Main Sequence stars were evident in the confined region previously surveyed in HST studies.…”

Section: Introductionmentioning

confidence: 99%

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A multi-wavelength analysis of M 81: insight on the nature of Arp's loop

Sollima

Paz

Martínez–Delgado

et al. 2010

A&A

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Context. The optical ring-like structure detected by Arp (1965) around M 81 (commonly referenced as "Arp's loop") represents one of the most spectacular features observed in nearby galaxies. Arp's loop is commonly interpreted as a tail resulting from the tidal interaction between M 81 and M 82. However, since its discovery the nature of this feature has remained controversial. Aims. Our primary purpose was to identify the sources of optical and infrared emission observed in Arp's loop. Methods. The morphology of Arp's loop has been investigated with deep wide-field optical images. We also measured its colors using IRAS and Spitzer-MIPS infrared images and compared them with those of the disk of M 81 and Galactic dust cirrus that fills the area where M 81 is located. Results. Optical images reveal that this peculiar object has a filamentary structure characterized by many dust features overlapping M 81's field. The ratios of far-infrared fluxes and the estimated dust-to-gas ratios indicate the infrared emission of Arp's loop is dominated by the contribution of cold dust that is most likely from Galactic cirrus. Conclusions. The above results suggest that the light observed at optical wavelengths is a combination of emission from i) a few recent star-forming regions located close to M 81, where both bright UV complexes and peaks in the HI distribution are found, ii) the extended disk of M 81 and iii) scattered light from the same Galactic cirrus that is responsible for the bulk of the far-infrared emission.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

A multi-wavelength analysis of M 81: insight on the nature of Arp's loop

Sollima

Paz

Martínez–Delgado

et al. 2010

A&A

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“…Recent (∼30-70 Myr) star formation has been found not only in the outskirts of M81 itself (Barker et al 2009) but also in nearby tidal dwarf galaxies such as Holmberg IX (Weisz et al 2008;Sabbi et al 2008), BK3N (Makarova et al 2002), and in other nearby tidal debris DeCesar et al 2004;Davidge 2008;de Mello et al 2008;Chiboucas et al 2009;). However, in all of these cases, the recent star formation has occurred in areas with higher H i column densities (N H i > 4 − 8 × 10 20 cm −2 ) than that observed in our field, and is thus consistent with the lack of recent (i.e., τ 10 8 yr) star formation in our field.…”

Section: Blue Starsmentioning

confidence: 99%

DEEPHST/ACS PHOTOMETRY OF THE M81 HALO

Durrell

Sarajedini

Chandar

2010

ApJ

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We present a deep color-magnitude diagram (CMD) for individual stars in the halo of the nearby spiral galaxy M81, at a projected distance of 19 kpc, based on data taken with the Advanced Camera for Surveys on the Hubble Space Telescope (HST). The CMD reveals a red giant branch (RGB) that is narrow and fairly blue, and a horizontal branch that has stars that lie mostly redward of the RR Lyrae instability strip. We derive a mean metallicity of [M/H] = −1.15 ± 0.11 and age of 9 ± 2 Gyr for the dominant population in our field, from the shape of the RGB, the magnitude of the red clump, and the location of the RGB bump. We compare our metallicity and age results with those found previously for stars in different locations within M81 and in the spheroids of other nearby galaxies.

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“…Reliable surface brightness measurements at these faint levels require accurate flat-field division, sky determination, bright star masking, among others (e.g. Barker et al 2009). …”

Section: Introductionmentioning

confidence: 99%

The MAGellanic Inter-Cloud (MAGIC) project – II. Slicing up the Bridge

Noël¹,

Conn²,

Read³

et al. 2015

Mon. Not. R. Astron. Soc.

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The origin of the gas in between the Magellanic Clouds (MCs), known as the Magellanic Bridge, has always been the subject of controversy. To shed light into this, we present the results from the MAGellanic Inter-Cloud II (MAGIC II) project aimed at probing the stellar populations in 10 large fields located perpendicular to the main ridge-line of H I in the Inter-Cloud region. We secured these observations of the stellar populations in between the MCs using the WFI (Wide Field Imager) camera on the 2.2 m telescope in La Silla. Using colour-magnitude diagrams, we trace stellar populations across the Inter-Cloud region. In good agreement with MAGIC I, we find significant intermediate-age stars in the Inter-Cloud region as well as young stars of a similar age to the last pericentre passage in between the MCs (∼200 Myr ago). We show here that the young, intermediate-age and old stars have distinct spatial distributions. The young stars correlate well with the H I gas suggesting that they were either recently stripped from the Small Magellanic Cloud (SMC) or formed in situ. The bulk of intermediate-age stars are located mainly in the Bridge region where the H I column density is higher, but they are more spread out than the young stars. They have very similar properties to stars located ∼2 kpc from the SMC centre, suggesting that they were tidally stripped from this region. Finally, the old stars extend to some 8 kpc from the SMC supporting the idea that all galaxies have a large extended metal-poor stellar halo.

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Resolving the Stellar Outskirts of M81: Evidence for a Faint, Extended Structural Component

Cited by 54 publications

References 96 publications

A multi-wavelength analysis of M 81: insight on the nature of Arp's loop

A multi-wavelength analysis of M 81: insight on the nature of Arp's loop

DEEPHST/ACS PHOTOMETRY OF THE M81 HALO

The MAGellanic Inter-Cloud (MAGIC) project – II. Slicing up the Bridge

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