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 MIPS Infrared Imaging of M31: Further Evidence for a Spiral-Ring Composite Structure

Gordon, K. D.; Bailin, Jeremy; Engelbracht, C. W.; Rieke, G. H.; Misselt, K. A.; Latter, William B.; Young, E. T.; Ashby, M. L. N.; Barmby, P.; Gibson, Brad K.; Hines, Dean C.; Hinz, J. L.; Krause, O.; Levine, Deborah A.; Marleau, F.; Noriega-Crespo, A.; Stolovy, S.; Thilker, David A.; Werner, M. W.

doi:10.1086/501046

Cited by 164 publications

(307 citation statements)

References 48 publications

(46 reference statements)

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“…We used the Spitzer-MIPS data at 24 μm, 70 μm, and 160 μm for M 31 (Gordon et al 2006) and M 33 (Tabatabaei et al 2007a). The basic data reduction and mosaicing was performed with the MIPS instrument Data Analysis Tool Version 2.90 (Gordon et al 2005).…”

Section: Datamentioning

confidence: 99%

“…The basic data reduction and mosaicing was performed with the MIPS instrument Data Analysis Tool Version 2.90 (Gordon et al 2005). For both galaxies, the sky and background sources in the MIPS maps were subtracted as detailed in Gordon et al (2006) and Tabatabaei et al (2007a).…”

Section: Datamentioning

confidence: 99%

“…(1) Beck et al (1998); (2) Tabatabaei et al (2007b); (3) Gordon et al (2006); (4) Tabatabaei et al (2007a); (5) Devereux et al (1994); (6) Hoopes & Walterbos (2000).…”

Section: Introductionmentioning

confidence: 99%

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Multi-scale radio-infrared correlations in M 31 and M 33: The role of magnetic fields and star formation

Tabatabaei

Berkhuijsen

Frick

et al. 2013

A&A

101

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Interstellar magnetic fields and the propagation of cosmic ray electrons have an important impact on the radio-infrared (IR) correlation in galaxies. This becomes evident when studying different spatial scales within galaxies. We investigate the correlation between the IR and free-free/synchrotron radio continuum emission at 20 cm from the two local group galaxies M 31 and M 33 on spatial scales between 0.4 and 10 kpc. The multi-scale radio-IR correlations have been carried out using a wavelet analysis. The free-free and IR emission are correlated on all scales, but on some scales the synchrotron emission is only marginally correlated with the IR emission. The synchrotron-IR correlation is stronger in M 33 than in M 31 on small scales (<1 kpc), but it is weaker than in M 31 on larger scales. Taking the smallest scale on which the synchrotron-IR correlation exists as the propagation length of cosmic ray electrons, we show that the difference on small scales can be explained by the smaller propagation length in M 33 than in M 31. On large scales, the difference is due to the thick disk/halo in M 33, which is absent in M 31. A comparison of our data with data on NGC 6946, the LMC and M 51 suggests that the propagation length is determined by the ratio of ordered-to-turbulent magnetic field strength, which is consistent with diffusion of CR electrons in the ISM. As the diffusion length of CR electrons influences the radio-IR correlation, this dependence is a direct observational evidence of the importance of magnetic fields for the radio-IR correlation within galaxies. The star-formation rate per surface area only indirectly influences the diffusion length as it increases the strength of the turbulent magnetic field.

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Section: Datamentioning

confidence: 99%

Section: Datamentioning

confidence: 99%

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Multi-scale radio-infrared correlations in M 31 and M 33: The role of magnetic fields and star formation

Tabatabaei

Berkhuijsen

Frick

et al. 2013

A&A

101

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“…M 31 is no exception; although Hubble classified it as normal type Sb, it is likely to possess a stellar bar. The presence of a bar in M 31 is suggested by its boxy bulge, which is conspicuous in infrared imaging 5,20 and is aligned almost parallel to the galaxys major axis. The boxy bulge might be an inflated bar, or it may hide a thinner parallel bar (at about 10 degrees from the major axis).…”

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confidence: 95%

An almost head-on collision as the origin of two off-centre rings in the Andromeda galaxy

Block

Bournaud

Combes

et al. 2006

Nature

Self Cite

116

160

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Abstract. The unusual morphology of the Andromeda Spiral (Messier 31, the closest spiral galaxy to the Milky Way) has long been an enigma. Although regarded for decades as showing little evidence of a violent history, M 31 has a well-known outer ring 1−7 of star formation at a radius of 10 kpc whose center is offset from the galaxy nucleus. In addition, the outer galaxy disk is warped as seen at both optical 8 and radio 9 wavelengths. The halo contains numerous loops and ripples. Here we report the discovery, based on analysis of previously-obtained data 10 , of a second, inner dust ring with projected dimensions 1.5 by 1 kpc and offset by ∼ 0.5 kpc from the center of the galaxy. The two rings appear to bedensity waves propagating in the disk.Numerical simulations offer a completely new interpretation for the morphology of M 31: both rings result from a companion galaxyplunging head-on through the center of the disk of M 31. The most likely interloper is M 32. Head-on collisions between galaxies are rare, but it appears nonetheless that one took place 210 million years ago in our Local Group of galaxies.Newly-acquired images 10 of M 31 secured by the Infrared Array Camera 11 (IRAC) onboard the Spitzer Space Telescope span the wavelength regime of 3.6 to 8.0 microns. These images offer unique probes of the morphologies of the stellar distribution and interstellar medium with no interference from extinction. Figure 1 shows the emission map of the interstellar medium at 8 microns, generated by subtracting a scaled 3.6 micron image (dominated by starlight) from the 8 micron image. The subtraction removes the contribution from stellar photospheres and leaves only the emission from dust grains 10 , which trace the interstellar medium of M 31. What is most striking in Figure 1 (and in the enlarged inset) is the presence of a complete though asymmetric inner ring of dust 6.9 by 4.4 arcmin in extent, translating to linear dimensions of about 1.5 by 1 kpc (assuming a distance 12 of 780 kpc). The inner ring lies between the two well known Baade spiral dust arms 13 , both of which are clearly seen in emission. The inner ring is elongated in a direction close to the minor axis and belongs to the central gas disk, which appears to be more face-on 14 . It is therefore not possible to know the inner rings precise ellipticity, but it is unlikely to be circular. IRAC imaging thus reveals two rings. The outer ring is offset by approximately 10 percent of its radius, while the inner ring is offset by about 40 percent or 0.5 kpc. The inner elliptical ring has been alluded to in earlier studies 15,16 , but all investigators have hitherto believed it to be a mini-spiral, related to a bar. Published Spitzer 24 micron images5 of M 31 show centrally-concentrated dust emission; the ring morphology is therefore disguised at these longer wavelengths. The IRAC images beautifully show the inner ring at high spatial resolution and furthermore confirm that this feature is a complete and continuous ring, even though offset and asymmetrical. Ther...

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“…• 4 (de Vaucouleurs et al 1991) so the new observations reach about 2 ×D 25 . The observations are summarized in Table 1. For the observation depth, we followed the Gordon et al 2006), and the extended observations (dotted lines). Stellar Structures in Galaxies (S 4 G, Sheth et al 2010) and specified eight 30-second frames per sky position.…”

Section: Mapping Strategy and Calibrationmentioning

confidence: 99%

The extended disc and halo of the Andromeda galaxy observed withSpitzer-IRAC

Ravandi

Barmby

Laine

et al. 2016

Mon. Not. R. Astron. Soc.

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We present the first results from an extended survey of the Andromeda galaxy (M31) using 41.1 h of observations by Spitzer-IRAC at 3.6 and 4.5 µm. This survey extends previous observations to the outer disc and halo, covering total lengths of 4.• 4 and 6.• 6 along the minor and major axes, respectively. We have produced surface brightness profiles by combining the integrated light from background-corrected maps with stellar counts from a new catalogue of point sources. Using auxiliary catalogues we have carried out a statistical analysis in colourmagnitude space to discriminate M31 objects from foreground Milky Way stars and background galaxies. The catalogue includes 426,529 sources, of which 66 per cent have been assigned probability values to identify M31 objects with magnitude depths of [3.6] = 19.0 ± 0.2, [4.5] = 18.7 ± 0.2. We discuss applications of our data for constraining the stellar mass and characterizing point sources in the outer radii.

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Sp i t zer MIPS Infrared Imaging of M31: Further Evidence for a Spiral-Ring Composite Structure

Cited by 164 publications

References 48 publications

Multi-scale radio-infrared correlations in M 31 and M 33: The role of magnetic fields and star formation

Multi-scale radio-infrared correlations in M 31 and M 33: The role of magnetic fields and star formation

An almost head-on collision as the origin of two off-centre rings in the Andromeda galaxy

The extended disc and halo of the Andromeda galaxy observed withSpitzer-IRAC

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