A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998

We study the nearby lenticular galaxy NGC 3998. This galaxy is known to host a low-power radio AGN with a kpc-size one-sided jet and a large, nearly polar H i disc. It is therefore a good system to study to understand the relation between the availability of cold-gas and the triggering of AGNs in galaxies. Our new WSRT data reveal two faint, S-shaped radio lobes extending out to ~10 kpc from the galaxy centre. Remarkably, we find that the inner H i disc warps back towards the stellar mid-plane in a way that mirrors the warping of the radio lobes. We suggest that the polar H i disc was accreted through a minor merger, and that the torques causing it to warp in the inner regions are also responsible for feeding the AGN. The “S” shape of the radio lobes would then be due to the radio jets adapting to the changing angular momentum of the accreted gas. The extended radio jets are likely poorly collimated, which would explain their quick fading and, therefore, their rarity in galaxies similar to NGC 3998. The fuelling of the central super-massive black hole is likely occurring via “discrete events”, suggested by the observed variability of the radio core and the extremely high core dominance, which we attribute to the formation and ejection of a new jet resulting from a recent fuelling event

LOFAR view of NGC 3998, a sputtering AGN

© ESO 2020. The original publication is available at https://doi.org/10.1051/0004-6361/201936796.Low-power radio sources dominate the radio sky. They tend to be small in size and dominated by their cores, but the origin of their properties and the evolution of their radio plasma are not well constrained. Interestingly, there is mounting evidence that low-power radio sources can significantly affect their surrounding gaseous medium and may therefore be more relevant for galaxy evolution than previously thought. In this paper, we present low radio frequency observations obtained with LOFAR at 147 MHz of the radio source hosted by NGC 3998. This is a rare example of a low-power source that is extremely dominated by its core, but that has two large-scale lobes of low surface brightness. We combine the new 147 MHz image with available 1400 MHz data to derive the spectral index over the source. Despite the low surface brightness, reminiscent of remnant structures, the lobes show an optically thin synchrotron spectral index (∼0.6). We interpret this as being due to rapid decollimation of the jets close to the core, to high turbulence of the plasma flow, and to entrainment of thermal gas. This could be the result of intermittent activity of the central active galactic nucleus, or, more likely, temporary disruption of the jet due to the interaction of the jet with the rich circumnuclear interstellar matter. Both would result in sputtering energy injection from the core, which would keep the lobes fed, albeit at a low rate. We discuss these results in connection with the properties of low-power radio sources in general. Our findings show that amorphous low surface brightness lobes should not be interpreted by default as remnant structures. Large deep surveys (in particular the LOFAR 150 MHz LoTSS and the recently started 1400 MHz Apertif survey) will identify a growing number of objects similar to NGC 3998 where these ideas can be further tested.Peer reviewedFinal Accepted Versio

Multiwaveband analysis of brightest GRB070125

We present a comprehensive multiwavelength analysis of the bright, long duration gamma-ray burst GRB 070125, comprised of observations in gamma-ray, X-ray, optical, millimeter and centimeter wavebands. Radio light curves show rapid flux variations, which are interpreted as due to interstellar scintillation, and are used to derive an upper limit of 2.4×10^17 cm on the radius of the fireball. Radio light curves and spectra suggest that the afterglow shock wave is moving in a dense medium. Our broadband modeling favors a constant density profile for the circumburst medium over a wind-like profile (R^−2). GRB 070125 is a burst with high radiative efficiency (>60%)

The Ursinus Weekly, April 27, 1964

Waiters guests at annual banquet • Bohl receives Fullbright to study abroad • Campus organizations conduct Spring elections: MSGA chooses officers; WSGA names class reps • Yocum selected to visit Russia • Mensch Mill site of annual Spring retreat • African trip, PAC forum event • Unadvertised Greek week promised to be one of the best • Cheerleaders • Spirit Committee • Women\u27s dorm officers • Meistersingers • Editorial: Supply and demand? • Next President: Henry Cabot Lodge • Slaves work for freedom with sweat, toil and bridge • Letters to the editor • Lacrosse loses 1st ever; Tennis blanked by Penn • Bears\u27 cindermen crunch Garnets • Penn relays have sad outcome • Winning week in Bears baseball • Softball swamps Penn foes 36-1 • Howard awarded science grant • Choir returns from New York • Greek gleanings • Classical music at Studio Cottage • Dr. Hetzel and American Indianhttps://digitalcommons.ursinus.edu/weekly/1272/thumbnail.jp

Effect of Gender on Atrial Electrophysiologic Changes Induced by Rapid Atrial Pacing and Elevation of Atrial Pressure

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74798/1/j.1540-8167.2001.00986.x.pd

Effects of Simultaneous Atrioventricular Pacing on Atrial Refractoriness and Atrial Fibrillation Inducibility: Role of Atrial Mechanoelectrical Feedback

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74794/1/j.1540-8167.2001.00043.x.pd

Clinical Value of the Postpacing Interval for Mapping of Ventricular Tachycardia in Patients with Prior Myocardial Infarction

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72569/1/j.1540-8167.1999.tb00640.x.pd

Differentiation of Atrial and Pulmonary Vein Potentials Recorded Circumferentially Within Pulmonary Veins

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72206/1/j.1540-8167.2002.00118.x.pd