Jets, arcs, and shocks: NGC 5195 at radio wavelengths

Abstract

We studied the nearby, interacting galaxy NGC 5195 (M 51b) in the radio, optical and X-ray bands. We mapped the extended, low-surface-brightness features of its radio-continuum emission; determined the energy content of its complex structure of shock-ionized gas; constrained the current activity level of its supermassive nuclear black hole. In particular, we combined data from the European Very Long Baseline Interferometry Network (∼1-pc scale), from our new e-MERLIN observations (∼10pc scale), and from the Very Large Array (∼100-1000-pc scale), to obtain a global picture of energy injection in this galaxy. We put an upper limit to the luminosity of the (undetected) flat-spectrum radio core. We find steep-spectrum, extended emission within 10 pc of the nuclear position, consistent with optically-thin synchrotron emission from nuclear star formation or from an outflow powered by an active galactic nucleus (AGN). A linear spur of radio emission juts out of the nuclear source towards the kpc-scale arcs (detected in radio, Hα and X-ray bands). From the size, shock velocity, and Balmer line luminosity of the kpc-scale bubble, we estimate that it was inflated by a long-term-average mechanical power ∼3-6 ×10 41 erg s −1 over the last 3-6 Myr. This is an order of magnitude more power than can be provided by the current level of star formation, and by the current accretion power of the supermassive black hole. We argue that a jet-inflated bubble scenario associated with previous episodes of AGN activity is the most likely explanation for the kpc-scale structures.

A Long Hard-X-Ray Look at the Dual Active Galactic Nuclei of M51 with NuSTAR

“…With our latest observation, where M51b was closer to the optical axis than previous observations, we have resolved the nuclear region finding that its true luminosity is even lower than previous estimates with L X =5×10 38 erg s −1 . This was similarly found by Rampadarath et al (2018) using the same Chandra data that we use. Annuar et al (in preparation) also analyze these data as part of an investigation into the N H distribution of AGN within 15 Mpc.…”

“…We use the position of the NIR source to inform us which is the nuclear X-ray source. Recent results from Rampadarath et al (2018) using high resolution (< 1 , ∼10 pc) e-MERLIN L (1-2 GHz) and C-band (4-8 GHz) radio data identify the same X-ray source as the nucleus.…”

NuSTAR observations of four nearby X-ray faint AGNs: low luminosity or heavy obscuration?

“…The bestfitting photon index measured is = 2.12 +0.61 −0.23 , and the APEC thermal component indicated a plasma temperature of kT = 0.95 +0.08 −0.16 keV. In general, our results are in agreement with those found by Brightman et al (2018) and Rampadarath et al (2018), who fitted the same data using slightly different models. We show the broad-band X-ray spectra of NGC 5195 in Fig.…”

“…L 3-8 keV, obs = 0.55 +0.09 −0.07 × 10 −13 and 1.08 +0.49 −0.41 × 10 −13 erg s −1 cm −2 , for our new data and the archival data, respectively. Investigation of the older Chandra data of NGC 5195, in which the nucleus and the off-nuclear source were unresolved by Rampadarath et al (2018), also revealed that the nucleus has varied by a factor of ∼3 between data taken in 2000 and 2012. The flux variability may be attributed to either the AGN or the nearby offnuclear source.…”

The curious activity in the nucleus of NGC 4151: jet interaction causing variability?

“…components C4E/C4W, we fix the source size to that of the beam and fit both the positions and flux densities of the sources simultaneously. The flux density uncertainties obtained from the fitting procedure are added in quadrature to a 5 per cent flux density bootstrapping uncertainty for MERLIN/e-MERLIN data (Rampadarath et al 2018). We report the extracted flux densities and associated uncertainties from the uv-matched data sets and are reported in Table 1.…”