Category Archives: News

Measurement of the black hole mass in NGC 1332 from high-resolution ALMA observations

In September 2015, ALMA observed the center of the galaxy NGC 1332 at angular resolution 0.044 arcseconds as part of our group’s Cycle 3 program. We observed the CO(2-1) rotational emission line with the goal of mapping the rotation speed of the molecular disk at the center of the galaxy. We received the processed data from ALMA in January. The data clearly show the expected signature of a compact central mass, in the form of a central rise in rotation speed, and we fit dynamical models to the ALMA data cube to determine the central mass. This is the first ALMA observation that has resolved the radius of influence of a supermassive black hole, and the measurement gives the mass of the black hole in NGC 1332 to 10% precision. Here are links to our published paper in the Astrophysical Journal Letters and the preprint (for those who can’t directly access the journal paper).

Collaborators on this project include Benjamin Boizelle (UCI graduate student), Jeremy Darling (Colorado), Andrew Baker (Rutgers), David Buote (UCI), Luis Ho (KIAA), and Jonelle Walsh (Texas A&M).

New paper: ALMA observations of NGC 1332

Our group has been working on a project to measure the masses of supermassive black holes in nearby elliptical galaxies using observations from the Atacama Large Millimeter/submillimeter Array. Our strategy is to search the Hubble Space Telescope archives to find ellipticals that have very nice, round, flat dust disks around their nuclei, and then use ALMA to measure the rotation of these disks using the CO(2-1) emission line. We initially start with observations at about 0.3 arcsec resolution to check for the presence of high-velocity rotation within the black hole’s sphere of influence (the small region in the galaxy’s center where the black hole’s gravitational pull is the dominant force), and then, in cases where we see rapid rotation at small scales, we then propose for higher resolution observations to measure the black hole mass accurately. Our first paper from this project was recently accepted for publication in ApJ. It describes our overall strategy, the initial observations of NGC 1332, and our dynamical modeling method. We do see clear evidence of rapid rotation, but because these initial observations don’t fully resolve the black hole’s sphere of influence, we don’t yet get an accurate measurement of the black hole mass from this observation. Higher-resolution ALMA observations can do the job. A key takeaway point from the paper is that there are a lot of potential systematic errors that cause trouble if your observations don’t resolve the black hole’s sphere of influence, and we argue that in order to get precise and accurate measurements of black hole masses, resolving this sphere of influence region is really crucial.

You can find a prepreint here:

http://arxiv.org/abs/1603.04523

Robotic reverberation mapping

The AGN Key Project Team of Las Cumbres Observatory Global Telescope Network (LCOGT) just released our first team paper,Bender_Rodriguez describing the first reverberation mapping measurement ever done using 100% robotically-acquired data from ground-based telescopes. We used the LCOGT telescopes to obtain spectra and photometry of the active galaxy Arp 151 over a 200-day period from late 2014 through mid-2015, found strong variations in the nuclear luminosity, and used the data to measure the size of the broad-line emitting region and to derive constraints on the mass of the central black hole. There are only a few telesecopes in the world that are currently capable of doing fully robotic spectroscopic observations, and this is a great demonstration of the capabilities of the FLOYDS spectrographs on the LCOGT Faulkes Telescopes.

Our paper was accepted for publication in the Astrophysical Journal Letters, and a preprint is available at arXiv:1510.07329. Congratulations to Stefano Valenti, David Sand, Keith Horne, and the whole team!

Update: our paper is published now, and is highlighted on the AAS Nova web site.

Partial solar eclipse

Last week I visited Oxford to attend a workshop on supermassive black holes at Wadham College.  On friday we got to see the partial solar eclipse through thick clouds.  I didn’t have the good camera with me, but here’s a picture from the phone camera that came out ok.

Big news for Lick Observatory

Google has just announced a donation of $1 million in support of UC’s Lick Observatory.  This is fantastic news  and will make a huge difference for science, education, and outreach programs at Lick.  Our group’s work on reverberation mapping of active galaxies with the Lick AGN Monitoring Project collaboration relies on the Lick Shane 3-meter telescope as our primary source of data. The Google support will help to ensure that Lick Observatory will continue to be a leading facility for research on black holes, supernovae, exoplanets, and many other topics.

http://newscenter.berkeley.edu/2015/02/10/google-gives-lick-observatory-1-million/

 

New paper on Hubble observations of nuclear star clusters in nearby spiral galaxies

Graduate student Daniel Carson’s paper on Hubble Space Telescope observations of nuclear star clusters in nearby spiral galaxies was recently accepted for publication in the Astronomical Journal.  The paper describes measurement of the structural properties of these clusters based on Hubble observations spanning ultraviolet, visible, and infrared wavelengths. You can find the preprint here.

Lick Observatory news

There’s a UCSC press release today announcing that Lick Observatory has received funding to implement a major upgrade for the Kast Spectrograph:

http://news.ucsc.edu/2014/12/kast-spectrograph.html

The Kast Spectrograph is the primary instrument for optical spectroscopic observations at the Shane 3-meter telescope at Lick.  Our group uses this spectrograph for reverberation mapping observations of active galaxies, to examine the environments of supermassive black holes and to measure the masses of the black holes.  The funding will support the installation of a new detector in the red camera of the spectrograph, which will mean a major improvement for the quality and efficiency of observations.  Many thanks to the Heising-Simons Foundation and to the Kast family for their generous support of Lick Observatory!

The corner of Barth & Einstein

Dan Maoz just sent me a picture of a street sign from his neighborhood: it’s the corner of Dr. Aaron Barth Street and Albert Einstein Street.  Or, more specifically, the Hebrew transliterates to Rehov Dr. Aharon Barth and Rehov Albert Einstein.  My namesake was apparently an important enough guy that he not only gets a street named after him, but he gets the “Dr.” in his street name while Dr. Einstein doesn’t merit that distinction.  Here’s the Wikipedia entry on the eminent Dr. Barth.

Oddly, Google Maps and Apple Maps mistransliterate my street name into English in different ways, despite the fact that the correct spelling is right there on the street sign: Google maps calls it “Bart Street”, and Apple Maps calls it “Barrett Street”.