The non-thermal superbubble in IC 10: the generation of cosmic ray electrons caught in the act

Heesen, V.; Brinks, E.; Krause, Martin; Harwood, J. J.; Rau, Urvashi; Rupen, M. P.; Hunter, Deidre A.; Chyży, K. T.; Kitchener, Ged

doi:10.1093/mnrasl/slu168

Cited by 30 publications

(35 citation statements)

References 45 publications

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“…Observational constraints for processes related to rotating black holes may be taken from measurements of type Ic supernovae associated with GRBs (e.g., Mazzali et al 2014), which are around 10 52 erg. Heesen et al (2015) found 10 52 erg in a superbubble around the >23 M black hole IC10-X1, plausibly related to a hypernova at its formation. If the strong explosions would be connected to a particular range of stellar masses, they might occur in a small time interval.…”

Section: Energy Productionmentioning

confidence: 91%

Gas expulsion in massive star clusters?

Krause

Charbonnel

Bastian

et al. 2016

A&A

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Context. Gas expulsion is a central concept in some of the models for multiple populations and the light-element anti-correlations in globular clusters. If the star formation efficiency was around 30 per cent and the gas expulsion happened on the crossing timescale, this process could preferentially expel stars born with the chemical composition of the proto-cluster gas, while stars with special composition born in the centre would remain bound. Recently, a sample of extragalactic, gas-free, young massive clusters has been identified that has the potential to test the conditions for gas expulsion. Aims. We investigate the conditions required for residual gas expulsion on the crossing timescale. We consider a standard initial mass function and different models for the energy production in the cluster: metallicity-dependent stellar winds, radiation, supernovae and more energetic events, such as hypernovae, which are related to gamma ray bursts. The latter may be more energetic than supernovae by up to two orders of magnitude. Methods. We computed a large number of thin-shell models for the gas dynamics, and calculated whether the Rayleigh-Taylor instability is able to disrupt the shell before it reaches the escape speed. Results. We show that the success of gas expulsion depends on the compactness index of a star cluster C 5 ≡ (M * /10 5 M )/(r h /pc), with initial stellar mass M * and half-mass radius r h . For given C 5 , a certain critical, local star formation efficiency is required to remove the rest of the gas. Common stellar feedback processes may not lead to gas expulsion with significant loss of stars above C 5 ≈ 1. Considering pulsar winds and hypernovae, the limit increases to C 5 ≈ 30. If successful, gas expulsion generally takes place on the crossing timescale. Some observed young massive clusters have 1 < C 5 < 10 and are gas-free at ≈10 Myr. This suggests that gas expulsion does not affect their stellar mass significantly, unless powerful pulsar winds and hypernovae are common in such objects. By comparison to observations, we show that C 5 is a better predictor for the expression of multiple populations than stellar mass. The best separation between star clusters with and without multiple populations is achieved by a stellar winds-based gas expulsion model, where gas expulsion would occur exclusively in star clusters without multiple populations. Single and multiple population clusters also have little overlap in metallicity and age. Conclusions. Globular clusters should initially have C 5 100, if the gas expulsion paradigm was correct. Early gas expulsion, which is suggested by the young massive cluster observations, hence would require special circumstances, and is excluded for several objects. Most likely, the stellar masses did not change significantly at the removal of the primordial gas. Instead, the predictive power of the C 5 index for the expression of multiple populations is consistent with the idea that gas expulsion may prevent the expression of multiple populations. On this bas...

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Section: Energy Productionmentioning

confidence: 91%

Gas expulsion in massive star clusters?

Krause

Charbonnel

Bastian

et al. 2016

A&A

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“…IC 10 was observed using the VLA in D-configuration at a central frequency of 6.2 GHz (project code: AH1006; Heesen et al 2015). To mitigate the effects of missing largeangular scale emission in these interferometric observations, single-dish data observed using the Effelsberg 100-m telescope were added to obtain total intensity image at 9.4 × 7.3 arcsec 2 angular resolution and rms noise of 15 µJy beam −1 (see Heesen et al 2015, for details).…”

Section: 2 Ghzmentioning

confidence: 99%

New insights into the interstellar medium of the dwarf galaxy IC 10: connection between magnetic fields, the radio–infrared correlation and star formation

Basu

Roychowdhury

Heesen

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the highest sensitivity and angular resolution study at 0.32 GHz of the dwarf irregular galaxy IC 10, observed using the Giant Metrewave Radio Telescope, probing ∼ 45 pc spatial scales. We find the galaxy-averaged radio continuum spectrum to be relatively flat, with a spectral index α = −0.34 ± 0.01 (S ν ∝ ν α ), mainly due to a high contribution from free-free emission. At 0.32 GHz, some of the Hii regions show evidence of free-free absorption as they become optically thick below ∼ 0.41 GHz with corresponding free electron densities of ∼ 11 − 22 cm −3 . After removing the free-free emission, we studied the radio-infrared relations on 55, 110 and 165 pc spatial scales. We find that on all scales the non-thermal emission at 0.32 and 6.2 GHz correlates better with far-infrared (FIR) emission at 70 µm than mid-infrared emission at 24 µm. The dispersion of the radio-FIR relation arises due to variations in both magnetic field and dust temperature, and decreases systematically with increasing spatial scale. The effect of cosmic ray transport is negligible as cosmic ray electrons were only injected 5 Myr ago. The average magnetic field strength (B) of 12 µG in the disc is comparable to that of large star-forming galaxies. The local magnetic field is strongly correlated with local star formation rate (SFR) as B ∝ SFR 0.35±0.03 , indicating a star-burst driven fluctuation dynamo to be efficient (∼ 10 per cent) in amplifying the field in IC 10. The high spatial resolution observations presented here suggest that the high efficiency of magnetic field amplification and strong coupling with SFR likely sets up the radio-FIR correlation in cosmologically young galaxies.

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“…The 26 Al measurement constitutes another piece of statistical information for bubbles and superbubbles. 26 Al decays on a timescale of 1 Myr, much shorter than typical superbubble lifetimes (e.g., Oey & García-Segura 2004;Bagetakos et al 2011;Heesen et al 2015). Hence, we may expect it to reflect internal dynamics.…”

Section: Introductionmentioning

confidence: 95%

²⁶Al kinematics: superbubbles following the spiral arms?

Krause

Diehl

Bagetakos

et al. 2015

A&A

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Context. High-energy resolution spectroscopy of the 1.8 MeV radioactive decay line of 26 Al with the SPI instrument onboard the INTEGRAL satellite has recently revealed that diffuse 26 Al has higher velocities than other components of the interstellar medium in the Milky Way. 26 Al shows Galactic rotation in the same sense as the stars and other gas tracers, but reaches excess velocities of up to 300 km s −1 . Aims. We investigate whether this result can be understood in the context of superbubbles, taking into account the statistics of young star clusters and H I supershells as well as the association of young star clusters with spiral arms. Methods. We derived energy output and 26 Al mass of star clusters as a function of the cluster mass by population synthesis from stellar evolutionary tracks of massive stars. Using the limiting cases of weakly and strongly dissipative superbubble expansion, we linked this to the size distribution of H I supershells and assessed the properties of possible 26 Al-carrying superbubbles. Results. 26 Al is produced by star clusters of all masses above ≈200 M , is roughly equally contributed over a logarithmic star cluster mass scale and strongly linked to the injection of feedback energy. The observed superbubble size distribution cannot be related to the star cluster mass function in a straightforward manner. To avoid the added volume of all superbubbles exceeding the volume of the Milky Way, individual superbubbles have to merge frequently. If any two superbubbles merge, or if 26 Al is injected off-centre into a larger HI supershell, we expect the hot 26 Al-carrying gas to obtain velocities of the order of the typical sound speed in superbubbles, ≈300 km s −1 before decay. For star formation coordinated by the spiral arm pattern which, inside co-rotation, is overtaken by the faster moving stars and gas, outflows from spiral arm star clusters would preferentially flow into the cavities that are inflated by previous star formation associated with this arm. These cavities would preferentially be located towards the leading edge of a given arm. Conclusions. This scenario might explain the 26 Al kinematics. The massive-star ejecta are expected to survive ≥10 6 yr before being recycled into next-generation stars.

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The non-thermal superbubble in IC 10: the generation of cosmic ray electrons caught in the act

Cited by 30 publications

References 45 publications

Gas expulsion in massive star clusters?

Gas expulsion in massive star clusters?

New insights into the interstellar medium of the dwarf galaxy IC 10: connection between magnetic fields, the radio–infrared correlation and star formation

²⁶Al kinematics: superbubbles following the spiral arms?

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The non-thermal superbubble in IC 10: the generation of cosmic ray electrons caught in the act

Cited by 30 publications

References 45 publications

Gas expulsion in massive star clusters?

Gas expulsion in massive star clusters?

New insights into the interstellar medium of the dwarf galaxy IC 10: connection between magnetic fields, the radio–infrared correlation and star formation

26Al kinematics: superbubbles following the spiral arms?

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²⁶Al kinematics: superbubbles following the spiral arms?