Megaparsec Relativistic Jets Launched From an Accreting Supermassive Black Hole in an Extreme Spiral Galaxy

Abstract

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 × 10 8 M ⊙ . 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 -2the standard paradigms for black hole growth and formation of relativistic jets in disk galaxies. Thus, it provides fundamental insight into accretion diskrelativistic jet coupling processes.

A deep Chandra observation of the hot gaseous halo around a rare, extremely massive and relativistic jet launching spiral galaxy

“…As in Bagchi et al (2014), we find that, scaling from the virial mass found for NGC 1961 in Bogdán et al (2013), we obtain M200 = 1.05 × 10 13 M⊙ and r200=450 kpc.…”

“…The close alignment of the inner and outer of the radio lobe pairs indicates that the spin axis of the central black hole has remained relatively stable over the timescale of ∼ 10 8 yr between jet triggering episodes (Bagchi et al 2014). Bagchi et al (2014) conclude that the galaxy and central black hole have evolved together quietly, with no major merging activity.…”

“…Bagchi et al (2014) conclude that the galaxy and central black hole have evolved together quietly, with no major merging activity. Bagchi et al (2014) found that this quiet evolution is likely due to the disklike nature of the pseudobulge, the absence of any tidal debris (such as plumes, stellar streams or shells), and the fact that the galaxy has a stable rotationally supported stellar disk featuring well formed spiral arms. The galaxy is also located in a relatively isolated galactic environment, with no nearby luminous galaxies, and it is not in the centre of a group or galaxy cluster.…”

“…This makes J2345-0449 one of the most massive known spiral galaxies. Another striking result obtained in Bagchi et al (2014) is the exceptionally large stellar velocity dispersion σ = 326(±59) km/s measured within the central (3 arcsec, or 4.3 kpc) region, higher than for the majority of bulge-less disks on such a spatial scale. This suggests a huge central concentration of mass, including a SMBH, and the lower limit from the optical data is > 2×10 8 M⊙.…”

“…Bagchi et al (2014) studied the kinematics of the optical Balmer Hα line observed with the IUCAA Girawali Observatory (IGO) 2m telescope, and found an extremely large rotation speed, Vrot = 371/sin(i) = 429 (±30) km s −1 , in the asymptotic flat region at r 10 kpc from the galactic center. This makes J2345-0449 one of the most massive known spiral galaxies.…”