Search Publications
Crimson Behemoth: A massive clumpy structure hosting a dusty AGN at z=4.91
Casey, Caitlin M.; Kartaltepe, Jeyhan S.; Koekemoer, Anton M. +40 more
The current paradigm for the co-evolution of galaxies and their supermassive black holes postulates that dust-obscured active galactic nuclei (AGNs) represent a transitional phase towards a more luminous and unobscured state. However, our understanding of dusty AGNs and their host galaxies at early cosmic times is inadequate due to observational l…
Processing of hydrocarbon dust in star-forming galaxies revealed with AKARI
Oyabu, Shinki; Kaneda, Hidehiro; Murata, Katsuhiro L. +5 more
Hydrocarbon dust is one of the dominant components of interstellar dust, which mainly consists of polycyclic aromatic hydrocarbons and aliphatic hydrocarbons. While hydrocarbon dust is thought to be processed in interstellar radiation fields or shocks, detailed processing mechanisms are not completely understood yet. We investigate the processing …
Multi-epoch X-ray spectral analysis of Centaurus A: Revealing new constraints on iron emission line origins
Tanimoto, Atsushi; Bamba, Aya; Hagino, Kouichi +3 more
We conduct X-ray reverberation mapping and spectral analysis of the radio galaxy Centaurus A to uncover its central structure. We compare the light curve of the hard X-ray continuum from Swift Burst Alert Telescope observations with that of the Fe K
Suzaku observation of an iron K-shell line in the spiral galaxy NGC 6946
Yamauchi, Shigeo; Inaba, Azusa; Anraku, Yumiko
An emission line at ~6.7 keV is attributable to an He-like iron K-shell transition, which indicates existence of a thin thermal plasma with a temperature of several keV. Using Suzaku archival data, we searched for the iron K-line from the spiral galaxy NGC 6946, and found it at 6.68 ± 0.07 keV at the 3.1σ level in the central $r\le {2.^{\prime }5}…
Discovery of diffuse radio source in Abell 1060
Nakazawa, Kazuhiro; Akahori, Takuya; Kurahara, Kohei +2 more
Non-thermal components in the intra-cluster medium (ICM), such as turbulence, magnetic field, and cosmic rays, imprint the past and current energetic activities of jets from active galactic nuclei (AGN) of member galaxies as well as disturbance caused by galaxy cluster mergers. Meter- and centimeter-radio observations of synchrotron radiation allo…
AGN number fraction in galaxy groups and clusters at z < 1.4 from the Subaru Hyper Suprime-Cam survey
Goto, Tomotsugu; Imanishi, Masatoshi; Schramm, Malte +20 more
One of the key questions on active galactic nuclei (AGN) in galaxy clusters is how AGN could affect the formation and evolution of member galaxies and galaxy clusters in the history of the Universe. To address this issue, we investigate the dependence of AGN number fraction (fAGN) on cluster redshift (zcl) and distance from t…
MeerKAT's view of double radio relic galaxy cluster Abell 3376
Nakanishi, Hiroyuki; Akamatsu, Hiroki; Takeuchi, Tsutomu T. +10 more
We present the initial results of our MeerKAT L-band observations of Abell 3376. We achieved higher (5″) angular resolution and better (~4 µ Jy beam-1) sensitivity compared to the previous observations. Our achieved sensitivity is only a factor of 2 larger than the thermal noise of MeerKAT. Astrometric and flux comparison of discr…
X-ray and optical spectroscopic study of a γ Cassiopeiae analog source π Aquarii
Tsujimoto, Masahiro; Hayashi, Takayuki; Morihana, Kumiko +1 more
γ Cas analog sources are a subset of Be stars that emit intense and hard X-ray emission. Two competing ideas for their X-ray production mechanism are (a) the magnetic activities of the Be star and its disk and (b) the accretion from the Be star to an unidentified compact object. Among such sources, π Aqr plays a pivotal role as it is one of the on…
XMM-Newton view of the shock heating in an early merging cluster, CIZA J1358.9-4750
Sato, Kosuke; Nakazawa, Kazuhiro; Gu, Liyi +10 more
CIZA J1358.9-4750 is a nearby galaxy cluster in the early phase of a major merger. The two-dimensional temperature map using XMM-Newton EPIC-PN observation confirms the existence of a high-temperature region, which we call the "hot region," in the "bridge region" connecting the two clusters. The ~500 kpc wide region between the south-east and nort…
On the influence of shock-cloud interactions on the nonthermal X-ray emission from the supernova remnant RCW 86
Vink, Jacco; Bamba, Aya; Sano, Hidetoshi +1 more
The effect of the surrounding environment of supernova remnant shocks on nonthermal X-rays from accelerated electrons, with or without interacting dense material, is an open issue. We conduct spatially resolved X-ray spectroscopy of the shock-cloud interacting region of RCW 86 with XMM-Newton. It is found that bright soft X-ray filaments surround …