The University of Tokyo · Physics and Astronomy
Professor J. D. Silverman's research lab specializes in observational astrophysics, focusing on active galactic nuclei (AGNs) and their host galaxies across cosmic time. The lab investigates the connection between AGN accretion, galaxy interactions, and star formation using multi-wavelength surveys—particularly X-ray, optical, and near-infrared data—from major facilities like Chandra, XMM-Newton, VLT, Keck, and Subaru. Key research directions include measuring the X-ray luminosity function of AGNs at high redshift, probing the role of galaxy interactions in triggering AGN activity, and studying the physical conditions in star-forming galaxies through emission-line spectroscopy. The lab emphasizes deep, multi-epoch surveys to understand the co-evolution of supermassive black holes and their host galaxies in the early universe.
Figures are computed from collected data and may differ slightly.
We present a measure of the hard (2-8 keV) X-ray luminosity function (XLF) of AGNs up to z ~ 5. At high redshifts, the wide area coverage of the Chandra Multiwavength Project is crucial to detect rare and luminous (LX > 1044 ergs s−1) AGNs. The inclusion of samples from deeper published surveys, such as the Chandra Deep Fields, allows us to span the lower LX range of the XLF. Our sample is selected from both the hard (z < 3, f2–8 keV > 6.3 × 10−16 ergs cm −2 s−1) and soft (z > 3, f0.
We present a study of the host galaxies of active galactic nucleus (AGN) selected from the zCOSMOS survey to establish if accretion onto supermassive black holes (SMBHs) and star formation are explicitly linked up to z ∼ 1. We identify 152 galaxies that harbor AGN, based on their X-ray emission (L0.5–10keV > 1042 erg s−1) detected by XMM-Newton observations of 7543 galaxies (iacs < 22.5). Star formation rates (SFRs), including those weighted by stellar mass, of a subsample are determined u
Close encounters between galaxies are expected to be a viable mechanism, as predicted by numerical simulations, by which accretion onto supermassive black holes can be initiated. To test this scenario, we construct a sample of 562 galaxies (M(*) > 2.5 x 10(10) M(circle dot)) in kinematic pairs over the redshift range 0.25 <z <1.05 that are more likely to be interacting than a well-matched control sample of 2726 galaxies not identified as being in a pair, both from the zCOSMOS 20k spectr
We present a spectroscopic survey of galaxies in the COSMOS field using the Fiber Multi-object Spectrograph (FMOS), a near-infrared instrument on the Subaru Telescope. Our survey is specifically designed to detect the Hα emission line that falls within the H-band (1.6–1.8 μm) spectroscopic window from star-forming galaxies with 1.4 < z < 1.7 and M_(stellar) ≳ 10^(10) M⊙. With the high multiplex capability of FMOS, it is now feasible to construct samples of over 1000 galaxies having spectro
We present the results of a program to acquire high-quality optical spectra of X-ray sources detected in the Extended-Chandra Deep Field-South (E-CDF-S) and its central 2 Ms area. New spectroscopic redshifts, up to z = 4, are measured for 283 counterparts to Chandra sources with deep exposures (t ~ 2-9 hr per pointing) using multi-slit facilities on both VLT (VIMOS) and Keck (DEIMOS), thus bringing the total number of spectroscopically identified X-ray sources to over 500 in this survey field. S
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