Research Highlights

JHU-SDSS Metal Absorber Catalog


The JHU-SDSS Metal Absorption Line Catalog (DR12) is available.


In ~400,000 quasar spectra from SDSS I-III, we have compiled ~100,000 Mg II/Fe II absorption-line systems. The method of catalog construction and the statistics and evolution of the Mg II absorbers are described in Zhu & Ménard 2013a


You can click the image or READ MORE button to go to the catalog webpage.

Near-ultraviolet Spectroscopy and Outflows


The next-generation dark energy surveys (SDSS-IV/eBOSS, DESI, PFS) will take observer-frame optical spectra of over 20 million galaxies/quasars at 0.5<z<2.5, providing rich datasets of rest-frame NUV spectroscopy. This composite image shows the spectra of about 12,000 emission-line galaxies (ELGs) from the eBOSS pilot observations. We found that the NUV window is an incredibly informative spectral region, containing signatures of key processes in galaxy formation and evolution, such as gas outflows and accretion.

Circumgalactic Medium and the Large-scale Distribution of Cool Gas


Circumgalactic medium (CGM) refers to the gas halo surrounding galaxies, contains signatures of key processes in galaxy formation and evolution, such as accretion and outflows, and is believed to account for the majority of the baryons in the Universe. I have been developing innovative statistical techniques to extract absorption information from large datasets (e.g., from SDSS) and also use the HST to observe FUV wavelength regions that are otherwise unaccessible. 

Low-resolution Spectroscopy (PRIMUS)


I spent the majority of my graduate-school time working on a low-resolution spectroscopic survey, the PRIsm MUlti-object Survey (PRIMUS). We (by we, I mean Scott Burles) installed a prism (image below, left) on IMACS, Magellan Baade Telescope. Because of the low resolution, we were able to observe about 2500 objects all at once. The whole program took 39 nights, including observations of multiple calibration fields. We obtained low-resolution spectra for 300,000 galaxies down to i_AB=23.5, from which we successfully measured about 130,000 unique redshifts from z~0.1 to z~1.

Elliptical Galaxy Formation


I developed an image-processing method to select high-quality elliptical galaxies based on their smooth surface brightness profile. From the SDSS survey, I selected a sample of about 2000 ellipticals at z<0.05 and performed a systematic study of the star-formation history of elliptical galaxies as a function of mass and environment.

My research has been based on the data collected with many wonderful telescopes: the SDSS Telescope, the Hubble Space Telescope, the Magellan I (Baade) Telescope, GALEX, WISE, Spitzer, the Keck Telescopes, GBT, VLBI, XMM, and Chandra and more.  Below is a photo of the SDSS Telescope I took during March 2014.

Johns Hopkins University

© 2016 Guangtun Ben Zhu

NASA Hubble Fellowship Program