A high-resolution wide-field radio survey of M51

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“…1. Other studies of the radio emission in M51 have also not detected a counterpart to ULX-7 (Maddox et al 2007;Rampadarath et al 2015). …”

Section: Radio Observationsmentioning

confidence: 86%

A variable ULX and possible IMBH candidate in M51a

Earnshaw

Roberts

Heil

et al. 2016

Mon. Not. R. Astron. Soc.

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“…• 48 29 rather than the centre of the galaxy, suggesting that NGC 628 does not have an active nucleus like M 51 (Rampadarath et al 2015). The brightest region of NGC 628 is part of the northern spiral arm, consisting of many H II regions, and is also bright in the infrared spectral range (Kennicutt et al 2011) and in H I line emission ).…”

Section: Effelsberg Mapsmentioning

confidence: 97%

Resolved magnetic structures in the disk-halo interface of NGC 628

Mulcahy

Beck

Heald

2017

A&A

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Context. Magnetic fields are essential to fully understand the interstellar medium and its role in the disk-halo interface of galaxies is still poorly understood. Star formation is known to expel hot gas vertically into the halo and these outflows have important consequences for mean-field dynamo theory in that they can be efficient in removing magnetic helicity. Aims. We aim to probe the vertical magnetic field and enhance our understanding of the disk-halo interaction of galaxies. Studying a face-on galaxy is essential so that the magnetic field components can be separated in 3D. Methods. We perform new observations of the nearby face-on spiral galaxy NGC 628 with the Karl G. Jansky Very Large Array (JVLA) at S -band (2.6-3.6 GHz effective bandwidth) and the Effelsberg 100-m telescope at frequencies of 2.6 GHz and 8.35 GHz with a bandwidth of 80 MHz and 1.1 GHz, respectively. Owing to the large bandwidth of the JVLA receiving system, we obtain some of the most sensitive radio continuum images in both total and linearly polarised intensity of any external galaxy observed so far. Results. The application of rotation measures synthesis to the interferometric polarisation data over this large bandwidth provides high-quality images of Faraday depth and polarisation angle from which we obtained evidence for drivers of magnetic turbulence in the disk-halo connection. Such drivers include a superbubble detected via a significant Faraday depth gradient coinciding with a H I hole. We observe an azimuthal periodic pattern in Faraday depth with a pattern wavelength of 3.7 ± 0.1 kpc, indicating Parker instabilities. The lack of a significant anti-correlation between Faraday depth and magnetic pitch angle indicates that these loops are vertical in nature with little helical twisting, unlike in IC 342. We find that the magnetic pitch angle is systematically larger than the morphological pitch angle of the polarisation arms which gives evidence for the action of a large-scale dynamo where the regular magnetic field is not coupled to the gas flow and obtains a significant radial component. We additionally discover a lone region of ordered magnetic field to the north of the galaxy with a high degree of polarisation and a small pitch angle, a feature that has not been observed in any other galaxy so far and is possibly caused by an asymmetric H I hole. Conclusions. Until now NGC 628 has been relatively unexplored in radio continuum but with its extended H I disk and lack of active star formation in its central region has produced a wealth of interesting magnetic phenomena. We observe evidence for two drivers of magnetic turbulence in the disk-halo connection of NGC 628, namely, Parker instabilities and superbubbles.

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“…Therefore, in all maps for the "ring" area we exclude a circle of radius R = 13.4 (centred on RA=13:29:52.432, Dec=+47:11:44.85). As shown by Rampadarath et al (2015), the bright and compact radio feature 27.8 north of the nucleus is aligned with the nuclear radio jet and is in all likelihood associated with past nuclear activity; thus, we also exclude from our analysis this component as a circle of radius R = 3.2 centred on RA=13:29:51.585, Dec=+47:12:07.61. These areas are indicated as white circles on the left panel of Fig.…”

Section: Star Formation Ratesmentioning

confidence: 99%

Dense gas is not enough: environmental variations in the star formation efficiency of dense molecular gas at 100 pc scales in M 51

Querejeta

Schinnerer

Schruba

et al. 2019

A&A

115

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It remains unclear what sets the efficiency with which molecular gas transforms into stars. Here we present a new VLA map of the spiral galaxy M51 in 33 GHz radio continuum, an extinction-free tracer of star formation, at 3 scales (∼100 pc). We combined this map with interferometric PdBI/NOEMA observations of CO(1-0) and HCN(1-0) at matched resolution for three regions in M51 (central molecular ring, northern and southern spiral arm segments). While our measurements roughly fall on the well-known correlation between total infrared and HCN luminosity, bridging the gap between Galactic and extragalactic observations, we find systematic offsets from that relation for different dynamical environments probed in M51; for example, the southern arm segment is more quiescent due to low star formation efficiency (SFE) of the dense gas, despite its high dense gas fraction. Combining our results with measurements from the literature at 100 pc scales, we find that the SFE of the dense gas and the dense gas fraction anti-correlate and correlate, respectively, with the local stellar mass surface density. This is consistent with previous kpc-scale studies. In addition, we find a significant anti-correlation between the SFE and velocity dispersion of the dense gas. Finally, we confirm that a correlation also holds between star formation rate surface density and the dense gas fraction, but it is not stronger than the correlation with dense gas surface density. Our results are hard to reconcile with models relying on a universal gas density threshold for star formation and suggest that turbulence and galactic dynamics play a major role in setting how efficiently dense gas converts into stars.

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A high-resolution wide-field radio survey of M51

Cited by 20 publications

References 112 publications

A variable ULX and possible IMBH candidate in M51a

A variable ULX and possible IMBH candidate in M51a

Resolved magnetic structures in the disk-halo interface of NGC 628

Dense gas is not enough: environmental variations in the star formation efficiency of dense molecular gas at 100 pc scales in M 51

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