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Testing Dark Matter by Looking for the Large Magellanic Cloud's Effect on the Milky Way

A recent research paper by grad student Nicolas Garavito-Camargo, professor Gurtina Besla, and collaborators has been picked up by AAS Nova. In it, they explore the effects of the gravitational interaction between the Large Magellanic Cloud and the Milky Way.

The following is a brief summary of the research:

The interaction between the Milky Way and the Large Magellanic Cloud provides a unique opportunity to test for the existence of dark matter. As a recently accreted, massive dwarf galaxy, the Large Magellanic Cloud induced a dark matter wake in the stellar and dark matter particles of the Milky Way halo. This article presents a suite of 8 high-resolution N-body simulations of the interaction between the Milky Way and the Large Magellanic Cloud to analyze the properties of the wake. These simulations show that the dark matter wake has a particular 6D (3 physical coordinates, radial velocity, and 2 proper motions)  kinematic signature that could be observable with current and next-generation surveys. The detection on the wake would confirm the existence of dark matter and potentially constrain the identity of the dark matter particle itself.

DESI Spectrograph on the Kitt Peak 4m Sees First Light: UArizona has Played a Significant Role

The new DESI spectrograph on the Mayall 4m telescope on Kitt Peak has seen first light. You can read the UArizona UANews press release HERE, and the Sky & Telescope article HERE.

Quoting from the UArizona press release: A new instrument mounted atop a telescope in Arizona aimed its robotic array of 5,000 fiber-optic “eyes” at the night sky to capture the first images of its unique view of galaxy light. It was the first test of the Dark Energy Spectroscopic Instrument, or  DESI, which is designed to explore the mystery of dark energy that makes up about 68% of the universe and is speeding up its expansion.

"DESI will give us a three-dimensional map of galaxies, quasars and intergalactic gas over a very large part of the universe," said Xiaohui Fan, a Regents Professor of astronomy at Steward Observatory. "By looking at that map, we can see how the structure of the universe has changed with cosmic time, and that gives us an idea of how fast the universe is expanding at any given time."

Fan explained that DESI can map 20 times more quasars and galaxies than previous surveys, which were limited to a fairly small number of snapshots over the course of the history of the cosmos.

"This survey will cover its history almost continuously, and that will allow us to measure the effect of dark energy with much better precision than before," he said.

UArizona scientists helped lay the groundwork for the DESI project by conducting an imaging survey that was used to identify the targets on which DESI will train its robotic eyes. The survey was completed using more than 360 nights of observing time on the university's Bok Telescope, which is located next to the Mayall Telescope on Kitt Peak.

The DESI collaboration has participation from nearly 500 researchers at 75 institutions in 13 countries, including more than a dozen UArizona students, postdoctoral fellows and faculty members.

Each of the ten planned spectrographs is equipped with three cameras, one each for ultraviolet, visible and infrared wavelengths.The UV channel for each spectrograph contains a thinned, UV/Blue-sensitive, 4096x4096 CCD produced at  UArizona's Imaging Technology Lab. ITL is directed by Dr. Michael Lesser, a Steward Observatory faculty member.

The spectra obtained with DESI will inform science that goes beyond the study of dark energy, according to Steward Observatory Director Buell Jannuzi. In addition to probing quasars and galaxies, DESI will take spectra of stars and help answer questions about the nature of dark matter, which is invisible but thought to far surpass the amount of visible matter in the universe. In addition, the survey will help scientists to better understand the evolution of galaxies and quasars over time, all questions that UArizona researchers are working on, he said.

"With DESI we are creating a legacy dataset that will support all kinds of astrophysics in the future," Jannuzi said.

(The figure on the front page of this article shows the ten robot positioners mounted at the top of the prime focus of the Mayall 4m telescope (photo courtesy NOAO). We also thank Daniel Stolte.)

Astrophoto Videos from Adam Block

Astrophotographer Adam Block of Steward Observatory has produced two videos using the Pomenis 180mm astrograph for wide-field imaging and the Mt Lemmon Sky Center telescopes for the higher-resolution imaging. The first video, HERE, is of the region of the constellation of Orion. The second, HERE, is of the region of the constellation Serpens. You can see more images HERE. The movies, images and cover photo here are all courtesy/copyright Adam Block.

Applications Being Accepted for Strittmatter Fellowship

The University of Arizona Dept of Astronomy and Steward Observatory is seeking applicants for the Peter A Strittmatter Fellowship for Advanced Study in Astronomy & Astrophysics. The job ad can be found HERE. For more information, please contact Professor Feryal Ozel (fozel) or Dr. Jared Males (jrmales). (Add "" to the prefix in the previous sentence.)

This postdoctoral fellowship provides an opportunity for a recent Ph.D. recipient to pursue an ambitious program of research in any area of theoretical, experimental, or observational astronomy or astrophysics. All of the observational and computational facilities of the Department of Astronomy and Steward Observatory are available to the Fellow, who is encouraged to conduct independent research and to develop collaborations with faculty, staff, and students.
The Strittmatter Fellow will receive  stipend of $65,000 per year, as well as access to a generous research fund to support their scientific program. This is a year-to-year Fellowship for up to 3 years and commences in fall 2020. Candidates must have completed all requirements for the Ph.D. in Astronomy or a related field before the start date of the Fellowship.
Review of applications begins Dec 3, 2019.

Assistant Professor Peter Behroozi Wins Packard Fellowship

We are pleased to announce that Assistant Professor Peter Behroozi is part of a nationwide class of 22 early-career scientists to be awarded a Packard Fellowship. He is one of only four astronomers to get this five-year, $875000 award in 2019. You can read about the Packard HERE and Daniel Stolte's UANews story HERE

Part of Peter's research will be to try to understand how supermassive black holes form so quickly in the early universe. Observations by others have shown that by the time the universe is 700 million years old (5% of its current age), there already exist supermassive black holes large enough to power the most luminous quasars. Current physical models simply cannot make such large black holes on the timescales that Nature does. Peter and his graduate student, Haowen Zhang, will attack this problem in the following way: "We are going to use our experience in creating millions of virtual universes containing billions of galaxies and apply it to generating new synthetic universes, this time filled with black holes,"  Peter says. "We will then compare our results to observational data of active, supermassive black holes and quasars at different times as well as to black holes closer to home."

Please join us in congratulating  Peter. Peter joins Astronomy/Steward Professors Dennis Zaritsky (1997) and Xiaohui Fan (2004) as Packard winners. 

Ruth McCutcheon

We are sad to tell you that our friend and colleague, Ruth McCutcheon, the Director of Development for the Department of Astronomy and Steward Observatory, passed away on July 29, 2019, after a courageous battle with cancer. We offer our deepest condolences to her children Grace and Henry, and to her parents Jim and Martha McCutcheon. Ruth was a leader in our efforts to connect with public and philanthropic contributors supporting the Department and Steward Observatory.  Her ability to build positive relationships between individuals and communities will be greatly missed by all of us.

Ruth, with the help of her family and friends, recently created the Ruth McCutcheon Steward Observatory Postdoctoral Fellows Research Endowment to help support the research of our Steward Observatory Prize Postdoctoral Fellows and postdoctoral researchers of Steward Observatory in general. Our academic community is brightened and strengthened by the presence and activities of our Fellows.  We are grateful  that Ruth recognized their key contributions and singled them out for her support. Please consider making a donation, in Ruth's honor, to this endowment.

HERE is a photo of Ruth in front of the oven at the Richard F. Caris Mirror Lab at the University of Arizona. HERE is a photo of Ruth doing what she loved best, communicating with people.

Yours most sincerely,

Buell Jannuzi

Head, Department of Astronomy

Director, Steward Observatory

(the eclipse photo of Ruth was taken by Alan Strauss, the other two linked photos by Cathi Duncan, and the front-page photo by Frank Gacon)