The H I Environment of the M101 Group

Mihos, J. Christopher; Keating, Katie M.; Holley‐Bockelmann, Kelly; Pisano, D. J.; Kassim, N. E.

doi:10.1088/0004-637x/761/2/186

Cited by 56 publications

(88 citation statements)

References 63 publications

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“…This means that the velocity field only crudely represents the overall kinematics. The heliocentric systemic velocity was found to be V sys = 208 ± 5 km s −1 , consistent with the value of 210 km s −1 found by Mihos et al (2012). 5 km s −1 are detected, even though the spectral resolution would allow detecting dispersions as low at 1.5 km s −1 .…”

Section: Datasupporting

confidence: 84%

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Is GBT 1355+5439 a dark galaxy?

Oosterloo

Heald

Blok

2013

A&A

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We present H i imaging of GBT 1355+5439 performed with the Westerbork Synthesis Radio Telescope. This is a dark H i object recently discovered close to the nearby galaxy M101. We find GBT 1355+5439 to be an H i cloud 5 × 3 arcmin in size. The total H i image and the kinematics show that the cloud consists of condensations that have small (∼10 km s −1 ) motions with respect to each other. The column densities of the H i are low; the observed peak value is 7.1 × 10 19 cm −2 . The velocity field shows a mild velocity gradient over the body of GBT 1355+5439, possibly due to rotation, but it may also indicate large-scale radial motions. Although our data are limited in sensitivity, at all positions the H i velocity dispersion is higher than 5 km s −1 and no narrow, cold, H i component is seen. Because its distance is not known, we considered various possibilities for the nature of GBT 1355+5439. Both the scenarios that it is a tidal remnant near M101 and that it is a dark dwarf companion of M101 meet difficulties. Neither do the data fit the properties of known compact high-velocity clouds in the Galactic halo exactly, but we cannot entirely exclude this option and deeper observations are required. We also considered the possibility that GBT 1355+5439 is a gas-rich dark minihalo in the outer regions of the Local Group. Interestingly, it would then have similar properties as the clouds of a proposed Local Group population recently found in the ALFALFA survey. In this case, the H i mass of GBT 1355+5439 would be about a few times 10 5 M , its size about 1 kpc, and the dynamical mass M dyn > 5 × 10 7 M . However, if GBT 1355+5439 is a dark Local Group object, the internal kinematics of the H i appears to be different from that of gas-dominated, almost dark galaxies of similar size.

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Section: Datasupporting

confidence: 84%

“…It has no optical counterpart, even in very deep optical images (Mihos et al 2012(Mihos et al , 2013. The immediate question is, of course, whether the object is a dark galaxy.…”

Section: Introductionmentioning

confidence: 99%

Is GBT 1355+5439 a dark galaxy?

Oosterloo

Heald

Blok

2013

A&A

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“…The results on NGC 6754 were later confirmed by Sánchez-Menguiano et al (2016a) by analysing the azimuthal abundance distribution of the galaxy. However, regarding M 101, a previous study performed by Li et al (2013) only observed marginal local metallicity inhomogeneities that the authors suggested may be linked to tidal features reported at that time (Mihos et al 2012). …”

Section: Dispersion Of the Gradient And Mixing Scalelengthmentioning

confidence: 82%

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

Sánchez-Menguiano

Sanchez

Pérez

et al. 2018

A&A

146

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We characterised the oxygen abundance radial distribution of a sample of 102 spiral galaxies observed with VLT/MUSE using the O3N2 calibrator. The high spatial resolution of the data allowed us to detect 14345 H ii regions with the same image quality as with photometric data, avoiding any dilution effect. We developed a new methodology to automatically fit the abundance radial profiles, finding that 55 galaxies of the sample exhibit a single negative gradient. The remaining 47 galaxies also display, as well as this negative trend, either an inner drop in the abundances (21), an outer flattening (10), or both (16), which suggests that these features are a common property of disc galaxies. The presence and depth of the inner drop depends on the stellar mass of the galaxies with the most massive systems presenting the deepest abundance drops, while there is no such dependence in the case of the outer flattening. We find that the inner drop appears always around 0.5 r e , while the position of the outer flattening varies over a wide range of galactocentric distances. Regarding the main negative gradient, we find a characteristic slope in the sample of α O/H = − 0.10 ± 0.03 dex/r e . This slope is independent of the presence of bars and the density of the environment. However, when inner drops or outer flattenings are detected, slightly steeper gradients are observed. This suggests that radial motions might play an important role in shaping the abundance profiles. We define a new normalisation scale ('the abundance scale length', r O/H ) for the radial profiles based on the characteristic abundance gradient, with which all the galaxies show a similar position for the inner drop (∼ 0.5 r O/H ) and the outer flattening (∼ 1.5 r O/H ). Finally, we find no significant dependence of the dispersion around the negative gradient with any property of the galaxies, with values compatible with the uncertainties associated with the derivation of the abundances.

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“…(Mihos et al 2012), the field strengths will have dropped to about 0.3 μG and 0.2 μG, respectively. Hence, the intragroup magnetic field strength is probably smaller than 0.3 μG, which is similar to the value estimated for a local group of irregular dwarf galaxies (Chyży et al 2011).…”

Section: Discussionmentioning

confidence: 98%

“…These maps show a complicated structure of many narrow, patchy spiral arms with large variations in pitch angle. The many linear arm segments and the asymmetry of the large-scale structure are attributed to a collision with the satellite galaxy NGC 5474 (Waller et al 1997;Kamphuis 1993;Mihos et al 2012). Kenney et al (1991) detected a bar in the centre in CO, which is also seen in Hα and near-infrared (NIR), but density waves are weak in M 101 (Kamphuis 1993).…”

Section: Introductionmentioning

confidence: 99%

Radio polarization and magnetic field structure in M 101

Berkhuijsen

Urbanik

Beck

et al. 2016

A&A

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We observed total and polarized radio continuum emission from the spiral galaxy M 101 at λλ 6.2 cm and 11.1 cm with the Effelsberg telescope. The angular resolutions are 2. 5 (=5.4 kpc) and 4. 4 (=9.5 kpc), respectively. We use these data to study various emission components in M 101 and properties of the magnetic field. Separation of thermal and non-thermal emission shows that the thermal emission is closely correlated with the spiral arms, while the non-thermal emission is more smoothly distributed indicating diffusion of cosmic ray electrons away from their places of origin. The radial distribution of both emissions has a break near R = 16 kpc (=7. 4), where it steepens to an exponential scale length of L 5 kpc, which is about 2.5 times smaller than at R < 16 kpc. The distribution of the polarized emission has a broad maximum near R = 12 kpc and beyond R = 16 kpc also decreases with L 5 kpc. It seems that near R = 16 kpc a major change in the structure of M 101 takes place, which also affects the distributions of the strength of the random and ordered magnetic field. Beyond R = 16 kpc the radial scale length of both fields is about 20 kpc, which implies that they decrease to about 0.3 μG at R = 70 kpc, which is the largest optical extent. The equipartition strength of the total field ranges from nearly 10 μG at R < 2 kpc to 4 μG at R = 22−24 kpc. As the random field dominates in M 101 (B ran /B ord 2.4), wavelength-independent polarization is the main polarization mechanism. We show that energetic events causing H i shells of mean diameter <625 pc could partly be responsible for this. At radii <24 kpc, the random magnetic field depends on the star formation rate/area, Σ SFR , with a powerlaw exponent of b = 0.28 ± 0.02. The ordered magnetic field is generally aligned with the spiral arms with pitch angles that are about 8 • larger than those of H i filaments.

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The H I Environment of the M101 Group

Cited by 56 publications

References 63 publications

Is GBT 1355+5439 a dark galaxy?

Is GBT 1355+5439 a dark galaxy?

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

Radio polarization and magnetic field structure in M 101

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