|cover main news cv research data public teaching ENJ|
Latest news in our group
A new paper finding a non-monotonic, strong metallicity dependence of the binary fraction of stars in the Milky Way by Hsiang-Chih Hwang et al.
Prof. Zakamska gave a department colloquium describing our group's efforts in stellar astrophysics; the recording is available here.
Two new exciting papers on the spectroscopic analysis of white dwarfs:
In this paper we use modern machine-learning techniques to analyzie white dwarf spectra and derive physical parameters such as gravity and temperature even in the absence of high-quality atmospheric models usually used for this purpose.
In this paper we make the first measurement of the white dwarf mass-radius relationship (and therefore of the white dwarf equation of state) across a wide range of masses. Not only that, but we perform this measurement using the effect of General Relativity in which a photon propagating from a surface of a massive object to the observer is subject to redshifting.
Our approved Early Release Science program for JWST was featured on the NASA website!
In this article our program is described in general science terms. The Principal Investigator is Dr. Dominika Wylezalek, formerly a postdoc in our group and now Group Leader at the University of Heidelberg. The Co-principal-investigators are Profs. Zakamska (JHU) and Veilleux (UMd College Park). JWST is NASA's new observatory operating mostly in the infrared which is scheduled to launch in October 2021.
Many congratulations to Dr. Kirsten Hall who defended her thesis today! Dr. Hall will be starting a postdoctoral fellowship at Harvard in Fall 2020. But before we can let her go, we have to subject her to the time-honored departmental traditions of the Defense Poster:
Lots of great news from the students in our group (and we need more great news now, so please keep going!):
Katherine Xiang, a student who has done research in our group (among many other things!) and Sydney Timmerman share the department's Kerr award. Katherine and Sydney have also both received NSF graduate fellowships, and Katherine further received Hertz fellowship to continue her research in bio-physics.
Ross Dempsey, formerly an undergraduate in our group and now a graduate student at Princeton, publishes our paper on the origin of the spectacular "Orion fingers" outflow, where we calculate the physical properties of the outflow and hypothesize that this outflow and others like it may lead to formation of unusual free-floating giant planets.
Nine (!) new students start an undergraduate research internship in our group in Summer 2020.
Kirsten Hall, a graduate student finishing her PhD this year with Profs. Zakamska and Marriage, receives the Schmidt Science Fellowship!! After graduation, she will take her Fellowship to Harvard University where she will study climate science and then will proceed to the Sub-Millimeter Array postdoctoral fellowship at Harvard's Center for Astrophysics.
While a major crisis is raging world-wide, we are trying to maintain sanity, productivity and positive outlook! I am glad to see my former group members and collaborators continuing interesting work on quasar feedback:
We are very thankful to Prof. Scott Tremaine for visiting our group! This was a very exciting group meeting. Sadly we only remembered to take the photo after half of the group dissipated, but here are some of us:
Both Vedant Chandra and Evan Petrosky receive Provost's Undergraduate Research Awards for the work done in our group. And Katherine Xiang, also a collaborator of our group, receives one for her science art work with David Nataf. Congratulations!!
A couple of new interesting papers from our group:
There is a postdoctoral position open in our group with a starting date in Fall 2020, to focus on star and planet formation, stellar variability and other exciting topics in Galactic astronomy. Applications are open until Dec 1, 2019.
JHU has outstanding opportunities for postdocs, including access to world-class survey and computational resources; access to strong postdoctoral community and postdoc career development resources; and access to research mentoring and teaching opportunities both at undergraduate and at graduate level.
There will also be openings in our group for new graduate students interested in Galactic (Milky Way) astronomy, stellar variability, star formation and stellar evolution. Interested prospective students should apply as described here (the application deadline is December 1, 2019. Interested students are welcome to indicate that they are interested in working in our group; however, a detailed research proposal is not required at this stage.
A new paper in the VODKA series, where we use variability-induced astrometric signals to place the most stringent constraints to date on the population of off-nucleus AGN (Shen, Hwang, Zakamska, Liu; ApJ Letters, in press)
A new exciting paper on a completely new topic for our group:
Lifetime of short-period binaries measured from their Galactic kinematics by Hwang and Zakamska, MNRAS, submitted, where we find that short-period binaries of 0.7-0.9 solar mass stars (period less than a day) take about 1 Gyr to form and about 10 Gyr to disappear from the population. The formation timescale may be consistent with the Kozai mechanism of binary formation, but the 10 Gyr disappearance time (shorter than the main sequence lifetime) is quite a mystery!
A couple of amazing papers by grad students in our group:
Detection of the Sunyaev-Zeldovich effect in stacked quasar specrtal energy distribution using the techniques pioneered by our group and in collaboration with the Atacama Cosmology Telescope (Hall et al., MNRAS, submitted)
A new method to search for supermassive black hole binaries in the 10-1000 pc regime not probed by any other existing techniques (Hwang et al., ApJ/AJ, submitted) -- our first paper in the series inspired by the Heising-Simons Foundation award to Yue Shen and Nadia Zakamska.
A couple of interesting papers on the exciting population of the extremely red quasars at peak redshift of quasar activity and galaxy formation:
Host galaxies of high-redshift obscured likely near-Eddington or super-Eddington quasars are not seemingly associated with ongoing major mergers (Zakamska et al., MNRAS, in press)
Extremely red quasars produce the most kinematically extreme ionized gas winds in the universe -- led by our close collaborators at UC Riverside (Perrotta et al., MNRAS)
A bitter-sweet moment as the current seniors graduate, including members of our research group who are off to great things in life: Anthony Flores, second from right, is headed to Stanford, and Wenzer Qin, 4th from left in the back row, is headed to MIT for grad school. Ross Dempsey (not shown) graduated earlier during the year and is headed to Princeton. Congratulations!!
JHU undergraduate team wins the International Theoretical Physics Olympiad for Undergraduates. The team -- David Carcamo, Ross Dempsey, Wenzer Qin, and Katherine Xiang -- includes three members affiliated with our group! The olympiad organizers notified the department that "their performance was exceptional, and their achievement is worthy of both recognition and celebration". Very impressive!
Kirsten Hall, Ross Dempsey and Wenzer Qin, all affiliated with our group, receive major departmental awards. Kirsten received E.J.Rhee travel award. Wenzer and Ross share the Donald E. Kerr award for the outstanding achievement by an undergraduate student. Both Wenzer and Ross also received NSF fellowships and will be pursuing graduate studies at MIT and Princeton, respectively. Congratulations!
Kirsten Hall, a graduate student in our group, is selected by JHU to attend the Lindau Nobel Laureate Meeting!
Vedant Chandra and Katherine Xiang, both undergraduate students affiliated with our group, receive Dean's Undergraduate Research Award for Summer 2019!
Our 5th Annual Quasar Day! (JHU/Drexel/Princeton)
Here is the schedule
Yue Shen (UIUC) and Nadia Zakamska receive a 2018 Scialog Collaborative Innovation Award
Kirsten Hall receives student observing support from the National Radio Astronomical Observatories for the ALMA proposal on which she serves as a Principal Investigator!
Our department is running a search for a Davis Postdoctoral Fellow, to start in Fall 2019: the AAS job ad.
Prospective graduate students wishing to start in Fall 2019 should apply as described here. A detailed research proposal is not required at this stage -- the committee is more interested in hearing about previous academic and research experiences and accomplishments. It is ok to indicate me as the faculty of interest on the statement without contacting me first.
Ross Dempsey successfully defends his Master's research project!
David Rivas, a long-time teaching assistant for Special Relativity / Waves, receives the E.J.Rhee award for flare in teaching. David follows Prasenjit Bose, Anirban Ghosh and Edwin Chan in receiving a teaching award for teaching performance in Special Relativity / Waves. Congratulations!
Kirsten Hall et al. present the result of complex halo-occupation-distribution modeling of faint infrared signal clustered around quasars. This is a unique probe of haloes and large-scale environments of star-forming galaxies at high redshift, which has allowed us to detect galaxy formation down-sizing across a wide range of redshifts for the first time.
Ai-Lei Sun et al. discover extended narrow-line regions of quasars in the Hyper Suprime-Cam data using a novel technique, in which the narrow-line emission can be successfully isolated using just broad-band imaging data.
Zhicheng He et al. measure the morphology of emission-line regions due to active black holes in the MaNGA survey. Not only are we able to detect the expected bi-conical morphology, but we find that the opening angles and inclinations of ionized regions are correlated with the infrared properties of AGN as expected in the unification model.
Wenzer Qin receives a Barry Goldwater Scholarship! Many congratulations! Wenzer published a paper based on research done in our group in summer 2018. She has also worked in Prof. Gritsan's and Prof. Kamionkowski's groups.
Hsiang-Chih Hwang receives the Gardner Fellowship. Many congratulations!!
Another batch of recently submitted papers:
Dempsey and Zakamska conduct a theoretical investigation of the size-luminosity relationship of quasars' narrow emission line regions. We find that in order to produce the ~10 kpc photo-ionized nebulae around powerful quasars, line-emitting clouds must be ionization-bounded, which means that emission-line regions contain 3-30 times more gas than is detectable via the emission lines.
Lambrides et al. present the largest study of molecular gas and polycyclic aromatic hydrocarbons using Spitzer spectra, finding that the excitation temperatures of the warm molecular gas are high in galaxies with active nuclei than without, a potential signature of feedback activity.
Goulding, Zakamska et al. present an X-ray study of extremely red quasars at high redshift. These objects are among the most highly X-ray obscured quasar populations, yet they are intrinsically luminous in X-ray.
Our group's proposal for Early Release Science with the James Webb Space Telescope was approved! Many congratulations to Principal Investigator Dr. Dominika Wylezalek!
Here are some of the papers submitted by our group members in the last few months:
Alexandroff R.M., Zakamska, N.L., et al. in the paper "Spectropolarimetry of high redshift obscured and red quasars" find fascinating spectropolarimetric signatures of equatorial outflows in extremely powerful quasars at the peak epoch of galaxy formation.
Wylezalek, D., Zakamska, N.L., et al. develop new methods of "Identification of active galactic nuclei in optical integral field unit surveys" and find that the standard diagnostic diagrams used for distinsguishing star-forming regions from active galactic nuclei based on single-fiber and nuclear spectroscopy need to be re-thought for extended ionized gas regions.
Hwang H.-C., Zakamska N.L. et al. discuss "Winds as the origin of radio emission in z=2.5 radio-quiet extremely red quasars" and find that low- and high-redshift obscured and red quasars form one relationship between the kinematics of ionized gas and radio luminosity among the radio-quiet quasars. This is an important clue about the origin of the radio emission in radio-quiet quasars which is not yet well understood.
Qin W., Nataf D., Zakamska N.L. et al. investigate a large sample of Mira-type variables in "Mira-based distance to the Galactic Center" and improve the understanding of extinction and metallicity corrections, making Miras more competitive as distance indicators.
Our department is now accepting applications for the Ph.D. program, with a starting date of August 2018, as described here. Our graduate program allows and encourages research rotations. Therefore, prospective students are welcome to indicate in the application that they are interested in joining our group; however, no detailed research proposal is required at this stage, and the admissions committee is more interested in past experiences and accomplishments in research and academics. Example student papers produced by our group are posted throughout this website, and prospective graduate students will have many opportunities to learn about specific projects that will be available in our group in Fall of 2018 after the admission decisions are made in winter 2018 and before committing to our program.
Undergraduate research interns Anthony Flores, Wenzer Qin and Channa Luke present at the Maryland Space Grant research symposium. Wenzer wins a 2nd place in the "Best speaker" competition! More information here.
Congratulations to Dr. Rachael Alexandroff on a successful Ph.D. defense! Dr. Alexandroff will be moving to the University of Toronto as a Canadian National Research Fellow in Fall 2017.
Welcome to the summer interns -- Suri, Anthony, Wenzer and Channa -- with many thanks to the Maryland Space Grant for the funding opportunities!
Postdoctoral supervisors are Dr. Kate Rowlands, Dr. Dominika Wylezalek, and Dr. David Nataf:
4th Annual Quasar Day (JHU/Drexel/Princeton)
Asa Stahl receives Provost's Undergraduate Research Award -- many congratulations! Previous recipients of PURA and DURA (Dean's Award) in our group include Michael Kelly, Kelly Lampayan, Georges Obied and Matthew Hill.
A press release on the discovery of a population of extremely red quasars with powerful outflows, related to the recent paper by Hamann, Zakamska et al. and the previous paper by Zakamska, Hamann et al. Many thanks to collaborator Fred Hamann at UC Riverside for spear-heading the press release.
Prospective graduate students wishing to start in September 2017 can apply as described here. We have lots of new content on the graduate program website, including profiles of recent alumni, graduation stats, and description of the program structure. Prospective students are welcome to indicate in the application that they are interested in joining our group; however, no detailed research proposal is required at this stage, and the admissions committee is more interested in past experiences and accomplishments.
Wylezalek, Schnorr Muller, Zakamska et al. (submitted to MNRAS) use Gemini GMOS intrument to zoom into the centers of nearby active galaxies studied with MaNGA integral field spectroscopic survey, to find strong nuclear outflows likely driven by black hole activity.
Hamann, Zakamska, Ross et al. (accepted to MNRAS) present a population of very intriguing high-redshift red quasars which may be linked to the strong outflow phase of galaxy evolution.
A paper led by Dominika Wylezalek finds observational evidence that specific star formation is suppressed in hosts of quasars with fastest outflows. This could be the long-sought sign of "negative" quasar feedback postulated in galaxy formation theory.
I was very pleased to see my Special Relativity textbook listed in "The Net Advance of Physics" Special Relativity library.
Dr. Dominika Wylezalek has been awarded the Provost's Postdoctoral Fellowship -- congratulations!
The largest catalog of type 2 quasars by Yuan, Strauss and Zakamska with lots of ancillary data is now publicly available here and the paper describing the catalog has been submitted to MNRAS. We are also releasing all [OIII] kinematics from the previous largest catalog by Reyes et al. 2008, Zakamska and Greene 2014.
News from the Department's Award Ceremony: Rachael Alexandroff receives the E.J.Rhee Travel Award and Joseph Cleary receives the Donald E. Kerr Memorial Prize -- congratulations!
Michael Kelly successfully presents his Master's thesis on active galactic nuclei in MaNGA data and will be receiving a Master's degree!
Alexandroff et al. 2016 -- a sensitive radio survey of obscured quasar candidates finds that radio emission in radio quiet quasars is extended on a few kpc scales and that it has steep spectral indices; this observation may be a critical clue in understanding the nature of the radio emission of radio-quiet quasars. Submitted to MNRAS.
The video of the public discussion of LIGO results at the Institute for Advanced Study, moderated by Director Robbert Dijkgraaf, with panelists Matias Zaldarriaga, Scott Tremaine, Nadia Zakamska and Doron Kushnir.
Wylezalek et al. 2016 -- a joint study of quasar hosts and their winds with HST and Gemini -- now in press in MNRAS.
Guilin Liu, a former postdoc in our group, will be moving to a faculty position at the University of Science and Technology in China in Fall 2016. Many congratulations!
Obied et al. 2015 -- detection of giant scattering cones in obscured quasars using the HST data and the implications for the unification model of active galaxies -- now in press in MNRAS.
Zakamska et al. 2015, Discovery of extreme [OIII]5007A outflows in high-redshift red quasars -- quasar-driven outflows proceeding at several thousand km/sec, likely on the scales of the host galaxy, submitted to MNRAS
The textbook "Theory of Special Relativity" by N.L.Zakamska is now publicly available.
Evidence for the Thermal Sunyaev-Zel'dovich Effect Associated with Quasar Feedback -- our novel view of quasar feedback in the paper by Devin Crichton et al. 2015
The Department of Physics and Astronomy at Johns Hopkins University is planning to offer a Davis Postdoctoral Fellowship in Astrophysics this year. The position will start in September 2016.
Prospective graduate students wishing to start in September 2016 can apply as described here.
Some papers our group submitted in the last couple of months include:
Dr. Dominika Wylezalek becomes inaugural Akbari-Mack Fellow! Congratulations to Dominika, and many thanks to Dr. Akbari and Mr. Mack for their support!
Kelly Lampayan and Georges Obied, both undergraduate researchers in Zakamska research group, share the Donald E. Kerr Memorial Award for outstanding Physics majors. Furthermore, Georges Obied qualifies for the M.A. degree! Prasenjit Bose receives Rowland Prize for innovation and excellence in teaching for outstanding work as teaching assistant in Special Relativity / Waves by Zakamska, following several years of excellence in teaching courses for non-majors. Prasenjit continues the streak of awards to teaching assistants for Special Relativity / Waves, following Edwin Chan (teaching award in May 2013) and Anirban Ghosh (teaching award in May 2014). Congratulations!
The materials for the IAS public lecture are posted here.