Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDiscovery of an unusual new radio source in the star-forming galaxy M82: Faint supernova, supermassive blackhole, or an extra-galactic microquasar?
80
0
0.0
(
0
)
Authors
T. W. B. Muxlow
Ask ChatGPT about the research
No Arabic abstract
A faint new radio source has been detected in the nuclear region of the starburst galaxy M82 using MERLIN radio observations designed to monitor the flux density evolution of the recent bright supernova SN2008iz. This new source was initially identified in observations made between 1-5th May 2009 but had not been present in observations made one week earlier, or in any previous observations of M82. In this paper we report the discovery of this new source and monitoring of its evolution over its first 9 months of existence. The true nature of this new source remains unclear, and we discuss whether this source may be an unusual and faint supernova, a supermassive blackhole associated with the nucleus of M82, or intriguingly the first detection of radio emission from an extragalactic microquasar.
rate research
Read More
In this Letter, we report the discovery of a new bright radio transient in M82. Using the Very Large Array, we observed the nuclear region of M82 at several epochs at 22 GHz and detected a new bright radio source in this galaxys central region. We find a flux density for this flaring source that is ~300 times larger than upper limits determined in previous observations. The flare must have started between 2007 October 29 and 2008 March 24. Over the last year, the flux density of this new source has decreased from ~100 mJy to ~11 mJy. The lightcurve (based on only three data points) can be fitted better with an exponential decay than with a power law. Based on the current data we cannot identify the nature of this transient source. However, a new radio supernova seems to be the most natural explanation. With its flux density of more than 100 mJy, it is at least 1.5 times brighter than SN1993J in M81 at the peak of its lightcurve at 22 GHz.
Radio galaxy phenomenon is directly connected to mass accreting, spinning supermassive black holes found in the active galactic nuclei (AGN). It is still unclear how the collimated jets of relativistic plasma on hundreds to thousands of kpc scale form, and why nearly always they are launched from the nuclei of bulge dominated elliptical galaxies and not flat spirals. Here we present the discovery of giant radio source J2345-0449 (z=0.0755), a clear and extremely rare counter example where relativistic jets are ejected from a luminous and massive spiral galaxy on scale of ~1.6 Mpc, the largest known so far. Extreme physical properties observed for this bulgeless spiral host, such as its high optical and infra-red luminosity, large dynamical mass, rapid disk rotation, and episodic jet activity are possibly the results of its unusual formation history, which has also assembled, via gas accretion from a disk, its central black hole of mass >2 x 10^8 M_sun. The very high mid-IR luminosity of the galaxy suggests that it is actively forming stars and still building a massive disk. We argue that the launch of these powerful jets is facilitated by an advection dominated, magnetized accretion flow at low Eddington rate onto this unusually massive (for a bulgeless disk galaxy) and possibly fast-spinning central black hole. Therefore, J2345-0449 is an extremely rare, unusual galactic system whose properties challenge the standard paradigms for black hole growth and formation of relativistic jets in disk galaxies. Thus, it provides fundamental insight into accretion disk -- relativistic jet coupling processes.
We have identified a new class of galaxy cluster using data from the Galaxy Zoo project. These clusters are rare, and thus have apparently gone unnoticed before, despite their unusual properties. They appear especially anomalous when the morphological properties of their component galaxies are considered. Their identification therefore depends upon the visual inspection of large numbers of galaxies, a feat which has only recently been made possible by Galaxy Zoo, together with the Sloan Digital Sky Survey. We present the basic properties of our cluster sample, and discuss possible formation scenarios and implications for cosmology.
Recent discoveries of recombining plasmas (RPs) in supernova remnants (SNRs) have dramatically changed our understanding of SNR evolution. To date, a dozen of RP SNRs have been identified in the Galaxy. Here we present Suzaku deep observations of four SNRs in the Large Magellanic Cloud (LMC), N49, N49B, N23, and DEM L71, for accurate determination of their plasma state. Our uniform analysis reveals that only N49 is in the recombining state among them, which is the first robust discovery of a RP from an extra-galactic SNR. Given that RPs have been identified only in core-collapse SNRs, our result strongly suggests a massive star origin of this SNR. On the other hand, no clear evidence for a RP is confirmed in N23, from which detection of recombination lines and continua was previously claimed. Comparing the physical properties of the RP SNRs identified so far, we find that all of them are categorized into the mixed-morphology class and interacting with surrounding molecular clouds. This might be a key to solve formation mechanisms of the RPs.
Galaxies experiencing intense star-formation episodes are expected to be rich in energetic cosmic rays (CRs). These CRs undergo hadronic interactions with the interstellar gases of their host to drive $gamma$-ray emission, which has already been detected from several nearby starbursts. Unresolved $gamma$-ray emission from more distant star-forming galaxies (SFGs) is expected to contribute to the extra-galactic $gamma$-ray background (EGB). However, despite the wealth of high-quality all-sky data from the Fermi-LAT $gamma$-ray space telescope collected over more than a decade of operation, the exact contribution of such SFGs to the EGB remains unsettled. We investigate the high-energy $gamma$-ray emission from SFGs up to redshift $z=3$ above a GeV, and assess the contribution they can make to the EGB. We show the $gamma$-ray emission spectrum from a SFG population can be determined from just a small number of key parameters, from which we model a range of possible EGB realisations. We demonstrate that populations of SFGs leave anisotropic signatures in the EGB, and that these can be accessed using the spatial power spectrum. Moreover, we show that such signatures will be accessible with ongoing operation of current $gamma$-ray instruments, and detection prospects will be greatly improved by the next generation of $gamma$-ray observatories, in particular the Cherenkov Telescope Array.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
