Mark A. Gurwell

Learn More
On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass(More)
Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by the accretion of matter onto supermassive black holes. Although the measured width profiles of such jets on large scales agree with theories of magnetic collimation, the predicted structure on accretion disk scales at the jet launch point has not been detected. We(More)
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. ABSTRACT We analyze the multi-frequency behavior of the quasar 3C 454.3(More)
Massive present-day early-type (elliptical and lenticular) galaxies probably gained the bulk of their stellar mass and heavy elements through intense, dust-enshrouded starbursts--that is, increased rates of star formation--in the most massive dark-matter haloes at early epochs. However, it remains unknown how soon after the Big Bang massive starburst(More)
Comets are some of the most primitive bodies left over from the Solar System's early history. They may preserve both interstellar material and material from the proto-solar nebula, and so studies of their volatile components can provide clues about the evolution of gases and ices, as a collapsing molecular cloud transforms into a mature planetary system.(More)
We have used the Submillimeter Array (SMA) to make the first interferometric observations (beam size ∼ 1 ′′ , or ∼ 400 pc) of the 12 CO J=6-5 line and 435 µm (690 GHz) continuum emission toward the central region (half power field of view 17 ′′) of the nearby ultra-luminous infrared galaxy (ULIRG) Arp 220. These observations resolve the eastern and western(More)
Context. Since 2001, the radio quasar 3C 454.3 has undergone a period of high optical activity, culminating in the brightest optical state ever observed , during the 2004–2005 outburst. The Whole Earth Blazar Telescope (WEBT) consortium has carried out several multifrequency campaigns to follow the source behaviour. Aims. The GLAST-AGILE Support Program(More)
Near a black hole, differential rotation of a magnetized accretion disk is thought to produce an instability that amplifies weak magnetic fields, driving accretion and outflow. These magnetic fields would naturally give rise to the observed synchrotron emission in galaxy cores and to the formation of relativistic jets, but no observations to date have been(More)