The University of Tokyo · Physics and Astronomy
Professor Yuki Isobe's research lab specializes in observational astrophysics, focusing on the chemical evolution and physical conditions of high-redshift star-forming galaxies using cutting-edge space-based telescopes such as the James Webb Space Telescope (JWST). The lab investigates electron densities, metallicity, and abundance ratios—particularly C/N and N/O—in early galaxies to understand the processes of early star formation and chemical enrichment. A key focus is identifying signatures of active galactic nuclei and their role in nitrogen enrichment, as well as exploring the origins of extreme chemical compositions in the early universe. The lab also engages in the study of bioactive lipid mediators, such as resolvin E3, linking inflammation resolution to human health and disease.
Figures are computed from collected data and may differ slightly.
Abstract We present electron densities n e in the interstellar medium (ISM) of star-forming galaxies at z = 4–9 observed by the JWST/NIRSpec GLASS, Early Release Observations, and CEERS programs. We carefully evaluate the line-spread functions of the NIRSpec instrument as a function of wavelength with the calibration data of a planetary nebula taken on board, and obtain secure [O ii ] λ λ 3726, 3729 doublet fluxes for 14 galaxies at z = 4.02–8.68 falling on the star formation main sequence with
Abstract We present chemical abundance ratios of 70 star-forming galaxies at z ∼ 4–10 observed by the JWST/NIRSpec Early Release Observations, GLASS, and CEERS programs. Among the 70 galaxies, we have pinpointed two galaxies, CEERS_01019 at z = 8.68 and GLASS_150008 at z = 6.23, with extremely low C/N ([C/N] ≲ −1), evidenced with C iii ] λλ 1907,1909, N iii ] λ 1750, and N iv ] λλ 1483,1486, which show high N/O ratios ([N/O] ≳ 0.5) comparable with the one of GN-z11, regardless of whether stellar
Uncontrolled inflammation is now considered to be a link between many widely occurring diseases. Thus, controlling the innate inflammatory response and its local chemical mediators has been receiving increasing attention. We recently identified a novel family of eicosapentaenoic acid (EPA)-derived mediators produced by eosinophils, denoted as resolvin E3 (RvE3), that possess potent anti-inflammatory actions both in vitro and in vivo. Carbons at 17 and 18 positions are asymmetric and thus the mol
Abstract We present Keck/LRIS follow-up spectroscopy for 13 photometric candidates of extremely metal-poor galaxies (EMPGs) selected by a machine-learning technique applied to the deep (∼26 AB mag) optical and wide-area (∼500 deg 2 ) Subaru imaging data in the EMPRESS survey. Nine out of the 13 candidates are EMPGs with an oxygen abundance (O/H) less than ∼10% solar value (O/H) ⊙ , and four sources are contaminants of moderately metal-rich galaxies or no emission-line objects. Notably, two out o
Selenoprotein P is a hepatokine with antioxidative properties that eliminate a physiologic burst of reactive oxygen species required for intracellular signal transduction. Serum levels of selenoprotein P are elevated during aging and in people with type 2 diabetes, non-alcoholic fatty liver disease, and hepatitis C. However, how serum levels of full-length selenoprotein P are regulated largely remains unknown, especially in the general population. To understand the significance of serum selenopr
ABSTRACT The unexpectedly high nitrogen-to-oxygen (N/O) ratios observed in high-redshift (z) galaxies have challenged our understanding of early star formation. Notably, many of these nitrogen-rich galaxies show signatures of active galactic nuclei (AGNs), suggesting a possible connection between black hole formation and nitrogen enrichment. To explore this connection, we analyse stacked spectra of $z=4{\!-\!}7$ broad-line and narrow-line AGNs using deep Near Infrared Spectrograph data from the
HC reflects fat mass and was positively associated with BEE, but not with DIT. In contrast, CC reflects fat-free mass, and was positively associated with BEE in both men and women, and with DIT in women.
Objective We aimed to identify obstructive sleep apnea syndrome (OSAS) severity indices reflecting the anthropometric and metabolic characteristics of patients with OSAS. Methods A total of 76 patients with OSAS underwent nasal continuous positive airway pressure (nCPAP). We also investigated the effects of nCPAP on OSAS-associated muscle sympathetic nerve activity (MSNA), risk for cardiovascular diseases, and insulin secretion and sensitivity. Results Among the OSAS severity indices, HbA1c was
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