A Galaxy without Dark Matter

This image of NGC1052-DF2 was taken by the Advanced Camera for Surveys on the Hubble Space Telescope. (Photo credit: NASA, ESA, and P. van Dokkum [Yale University])

In a paper published in Nature last week, researchers from Yale, San Jose State University, University of Toronto, Harvard, and the Max Planck Institute for Astronomy revealed a startling discovery: they have found a faint galaxy that contains no dark matter. This discovery is startling and important because it establishes for the first time that “dark” matter, making up about 85% of the mass in the universe and so called because of its lack of interaction with light, is not necessarily present in every galaxy as previously thought. This demonstrates that dark matter is a substance that exists independently and is not merely an artefact of gravity in galaxies. The discovery further requires that new theories be developed for how to form galaxies without dark matter as a gravitational incubator.

SJSU Physics and Astronomy Professor Aaron Romanowsky, a co-author of the paper, and his colleagues were able to demonstrate the absence of dark matter in the galaxy, known as NGC1052-DF2, by analyzing the velocities of star clusters orbiting the galaxy from spectroscopic observations made at the W. M. Keck Observatory on Mauna Kea, Hawaii. From the velocity distribution they measured the mass in the galaxy and thereby ruled out the presence of significant amounts of dark matter.

Another account of this groundbreaking work can be found from the Hubble Space Telescope.

Khatami Honored for his Research in Condensed Matter Physics

Research from the lab of Physics and Astronomy Professor Ehsan Khatami and his team of research students has been receiving a lot of attention lately (including in our Oct. 3 post). A recently article by Khatami and SJSU students Kevin Ch’ng and Nick Vazquez titled “Unsupervised machine learning account of magnetic transitions in the Hubbard model” published in Physical Review E has been featured on Kaleidoscope. This honor follows the announcement in December that Khatami will be honored as one of two Early Career Investigator Award winners by the SJSU Research Foundation. In her announcement of the award, Associate Vice President Pamela Stacks wrote:

“The SJSU Research Foundation Early Career Investigator Awards recognize tenure-track SJSU faculty who have excelled in areas of research, scholarship or creative activity (RSCA) as evidenced by their success in securing funds for RSCA, publishing in peer-reviewed journals, and carrying out other important scholarly and creative activities at an early or beginning point in their careers at SJSU. One award goes to a faculty member in the College of Science or the College of Engineering, and another is made to a faculty member from the other colleges combined. Each winner receives a cash award of $1,000 to be used at their discretion.

In the three years since he joined the Physics & Astronomy faculty, Ehsan Khatami has made remarkable contributions to the computational infrastructure and capabilities in the department and college; published extensively in the highest-ranked science journals, including one paper in Nature and two in Science, with co-authors from institutions like MIT, Harvard, and Princeton; and served as research mentor for seven undergraduate and six graduate students.

Dr. Khatami was hired to help expand the department’s offerings in computational physics throughout the curriculum. The first project he undertook was to build the department’s first modern high-performance computational cluster, which is used extensively by students enrolled in big-data courses and undertaking computational research. Because of his computational expertise, Dr. Khatami joined Dr. Sen Chiao as Co-PI on the successful NSF Major Research Instrumentation proposal that funded the $900K supercomputer now installed at the Research Foundation. He also was awarded a three-year NSF Research at Undergraduate Institutions grant for his project on “Disorder in Strongly Correlated Systems.”

Dr. Khatami and his students have expanded their research focus to apply machine learning techniques to the solution of complex quantum problems, and one of his graduate students has been the lead author on two papers, one already published and highlighted in Physical Review X. This paper is just one of the 12 published and two submitted papers that Dr. Khatami and his collaborators have produced since he arrived at SJSU.

In addition, Dr. Khatami has been recognized by others outside the institution. In 2016, he was named one of only seven Kavli Institute for Theoretical Physics (KITP) Scholars. This three-year visiting position is awarded to faculty at teaching-intensive institutions who engage in ongoing research activity, and provides support for six weeks of travel to the KITP program at UC Santa Barbara. He has given several invited talks and has participated in national and international conferences, all of which spread the word about the outstanding research being done at San José State University.”

New Research Reveals Surprising Magnetic Effects in Ultracold Lithium Atoms

Individual lithium atoms imaged in a spin-imbalanced Fermi gas trapped in an optical lattice

In a paper just published in the journal of Science, experimentalists at Princeton, led by Prof. Waseem Bakr, and several theorists including Prof. Ehsan Khatami of SJSU, report their direct observation of an exotic magnetic phase of matter with ultracold atoms that could help explain how high-temperature superconductivity — the complete loss of resistance to electric flow— works. By applying a strong magnetic field researchers find that atoms form a checkerboard pattern in the alignment of their intrinsic magnetic fields while slightly leaning away from each other, a state termed “canted antiferromagnetism”. Prof. Khatami used a state-of-the-art numerical technique to obtain numerical results for comparison to the experimental measurements based on a well-known theoretical model, which was crucial in guiding the experiments and allowing the team to characterize the new phase of atoms. The study is an important step towards better understanding electronic properties of solids, which can help us design better materials with specific properties we can harness in technology, energy and industry applications.

Study Reveals a New Trick in a Microscopic Arms Race

Image from JoVE Science Education Database.

C. elegans, a nematode (roundworm) that lives in soil, feeds on bacteria that grow on decaying organic matter. But one genus of bacteria, Streptomyces, fights back against these nematode predators with chemical toxins known as nematicides. Indeed avermectin, a nematicide produced by Streptomyces avermitilis discovered in 1978, is such a valuable drug in the treatment of parasitic worms in humans, that its discoverers were awarded a Nobel Prize in Physiology or Medicine in 2015.

Now a new study, published in the journal eLife, reveals how nematodes escape when they enter into nematicide-containing soil: they sense dodecanoic acid, a tell-tale sign that the Streptomyces bacteria are nearby. The study, involving a multidisciplinary collaboration between SJSU and UCSF, has found that C. elegans detects the Streptomyces-produced dodecanoic acid trail via a specific chemosensory receptor expressed in sensory neurons in the head and tail, and hastens a retreat from the area before succumbing to the nematocides.

The scientific team making this discovery was an exemplar of multidisciplinary research including students and faculty researchers from six departments at two universities. The team was led by Profs. Miri VanHoven (Biological Sciences) and Laura Miller Conrad (Chemistry) and included Profs. Daryl Eggers (Chemistry), Martina Bremer (Mathematics and Statistics), and Sami Khuri (Computer Science) all from SJSU and Prof. Noelle L’Etoile (Cell and Tissue Biology)  and Dr. Colleen O’Loughlin (Bioengineering and Therapeutic Sciences) from UCSF.

Professor Pesek Wins National Award for Research at an Undergraduate Institution

Professor Joseph Pesek

The American Chemical Society has recognized Professor Joseph Pesek’s substantial and impactful research contributions with the ACS Award for Research at an Undergraduate Institution sponsored by the Research Corporation for Science Advancement. The award honors “a chemistry faculty member whose research in an undergraduate setting has achieved wide recognition and contributed significantly to chemistry and to the professional development of undergraduate students.”

Prof. Pesek’s research in the area of separations science as applied to metabolomics and proteomics has been highly influential leading both to commercial products and to an amazingly prolific academic record with over 230 peer reviewed publications and over 250 seminars, guest lectures, and presentations. During his career at SJSU, Prof. Pesek has mentored over 100 undergraduate research students and 100 Master’s students.