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ALMA OBSERVATION OF THE 658 GHz VIBRATIONALLY EXCITED H<sub>2</sub>O MASER IN ORION KL SOURCE I
Hirota, Tomoya,Kim, Mi Kyoung,Honma, Mareki American Astronomical Society 2016 The Astrophysical journal Vol.817 No.2
<P>We present an observational study of the vibrationally excited H2O line at 658 GHz (v(2) = 1, 1(1,0)-1(0,1)) toward Orion KL using the Atacama Large Millimeter/Submillimeter Array (ALMA). This line is clearly detected at the position of the massive protostar candidate, Source I. The spatial structure is compact, with a size of about 100 AU, and is elongated along the northeast-southwest low-velocity (18 km(-1)) bipolar outflow traced by 22 GHz H2O masers, SiO masers, and thermal SiO lines. A velocity gradient can be seen perpendicular to the bipolar outflow. The overall spatial and velocity structure seems to be analogous to that of the 321 GHz H2O maser line previously detected with ALMA and vibrationally excited SiO maser emission. The brightness temperature of the 658 GHz H2O line is estimated to be higher than 2 x 10(4) K, implying that it is emitted via maser action. Our results suggest that the 658 GHz H2O maser line is emitted from the base of the outflow from a rotating and expanding accretion disk as observed for the SiO masers and the 321 GHz H2O maser. We also search for two other H2O lines at 646 GHz (9(7,3)-8(8,0) and 9(7,2)-8(8,1)), but they are not detected in Orion KL.</P>
MEASURING THE CORE SHIFT EFFECT IN AGN JETS WITH THE EXTENDED KOREAN VLBI NETWORK
정태현,Richard Dodson,Maria J. Rioja,변도영,Mareki Honma,Jamie Stevens,Pablo de Vicente,손봉원 한국천문학회 2015 Journal of The Korean Astronomical Society Vol.48 No.5
We present our efforts for extending the simultaneous multi-frequency receiver system of the Korean Very Long Baseline Interferometry (VLBI) Network (KVN) to global baselines in order to measure the frequency-dependent position shifts in Active Galactic Nuclei (AGN) jets, the so called core shift effect, with an unprecedented accuracy (a few micro-arcseconds). Millimeter VLBI observations with simultaneous multi-frequency receiver systems, like those of the KVN, enable us to explore the innermost regions of AGN and high precision astrometry. Such a system is capable of locating the frequency dependent opacity changes accurately. We have conducted the feasibility test-observations with the interested partners by implementing the KVN-compatible systems. Here we describe the science case for measuring the core shift effect in the AGN jet and report progress and future plans on extending the simultaneous multi-frequency system to global baselines.}
A HOT MOLECULAR CIRCUMSTELLAR DISK AROUND THE MASSIVE PROTOSTAR ORION SOURCE I
Hirota, Tomoya,Kim, Mi Kyoung,Kurono, Yasutaka,Honma, Mareki University of Chicago Press for the American Astro 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.782 No.2
We report new Atacama Large Millimeter/Submillimeter Array (ALMA) observations of a circumstellar disk around Source I in Orion KL, an archetype of massive protostar candidates. We detected two ortho-H2O lines at 321 GHz (10(2,9)-9(3,6)) and 336 GHz (nu(2) = 1, 5(2,3)-6(1,6)) for the first time in Source I. The latter one is in a vibrationally excited state at the lower state energy of 2939 K, suggesting evidence of hot molecular gas close to Source I. The integrated intensity map of the 321 GHz line is elongated along the bipolar outflow while the 336 GHz line map is unresolved with a beam size of 0 ''.4. Both of these maps show velocity gradients perpendicular to the bipolar outflow. The velocity centroid map of the 321 GHz line implies a spatial and velocity structure similar to that of vibrationally excited SiO masers tracing the root of the outflow emanating from the disk surface. In contrast, the 336 GHz line is most likely emitting from the disk midplane with a diameter of 0 ''.2 (84 AU) as traced by radio continuum emission and a dark lane devoid of the vibrationally excited SiO maser emission. The observed velocity gradient and the spectral profile of the 336 GHz H2O line can be reconciled with a model of an edge-on ring-like structure with an enclosed mass of >7M(circle dot) and an excitation temperature of >3000 K. The present results provide further evidence of a hot and neutral circumstellar disk rotating around Source I with a diameter of similar to 100 AU scale.
ALMA IMAGING OF MILLIMETER/SUBMILLIMETER CONTINUUM EMISSION IN ORION KL
Hirota, Tomoya,Kim, Mi Kyoung,Kurono, Yasutaka,Honma, Mareki IOP Publishing 2015 The Astrophysical journal Vol.801 No.2
<P>We have carried out high-resolution observations with the Atacama Large Millimeter/Submillimeter Array (ALMA) of continuum emission from the Orion Kleinmann-Low (KL) region. We identify 11 compact sources at ALMA band 6 (245 GHz) and band 7 (339 GHz), including the Hot Core, Compact Ridge, SMA1, IRc4, IRc7, and a radio source I (Source I). A spectral energy distribution (SED) of each source is determined by using previous 3 mm continuum emission data. Physical properties such as size, mass, hydrogen number density, and column density are discussed based on the dust graybody SED. Among 11 identified sources, Source I, a massive protostar candidate, is a dominant energy source in Orion KL. We extensively investigate its SED from centimeter to submillimeter wavelengths. The SED of Source I can be fitted with a single power-law index of 1.97, suggesting an optically thick emission. We employ the H- free-free emission as an opacity source of this optically thick emission. The temperature, density, and mass of the circumstellar disk associated with Source I are constrained by the SED of H- free-free emission. Still, the fitting result shows a significant deviation from the observed flux densities. Combined with the thermal dust graybody SED to explain excess emission at higher frequency, a smaller power-law index of 1.60 for the H- free-free emission is obtained in the SED fitting. The power-law index smaller than two would suggest a compact source size or a clumpy structure unresolved with the present study. Future higher resolution observations with ALMA are essential to reveal more detailed spatial structure and physical properties of Source I.</P>
Probing the precise location of the radio core in the TeV blazar Mrk 501 with VERA at 43 GHz
Koyama, Shoko,Kino, Motoki,Doi, Akihiro,Niinuma, Kotaro,Hada, Kazuhiro,Nagai, Hiroshi,Honma, Mareki,Akiyama, Kazunori,Giroletti, Marcello,Giovannini, Gabriele,Orienti, Monica,Isobe, Naoki,Kataoka, Jun Astronomical Society of Japan 2015 Publications of the Astronomical Society of Japan Vol.67 No.4
Toward early scientific results on AGNs: 'KAVA'(KVN and VERA array) joint AGN WG report
손봉원,이상성,Sohn, Bong Won,Kino, Motoki,Niinuma, Kotaro,Lee, Sang-Sung,Honma, Mareki,Nagai, Hiroshi,Sascha, Sascha Trippe,Jung, Taehyun 한국천문학회 2012 天文學會報 Vol.37 No.2
We report the results of KVN-VERA('KAVA'; KVN and VERA Arrary) AGN WG test observation in 2011 and 2012. The results from these commisioning years show that 'KAVA' is able to produce noble images of radio loud AGNs at 22 and 43GHz. This dedicated high frequency VLBI facility will be especially competitive for the regions where conventional low freuquency facilities see the optically thick part of synchrotron radiation. In the second part of this talk, we report the early science activities of the AGN WG. Sgr A*, Jet acceleration zone of M87, extremely young radio galaxies are the prime cadidates of the joint activities. Lastly we will stress how the phase-referencing 'KAVA' does enhance the imaging sensitivity and open new era of VLBI AGN researches.
Guang-Yao Zhao,Taehyun Jung,Bong Won Sohn,Motoki Kino,Mareki Honma,Richard Dodson,Maria Rioja,Seog-Tae Han,Katsunori Shibata,Do-Young Byun,Kazunori Akiyama,Juan-Carlos Algaba,Tao An,Xiaopeng Cheng,Ilj 한국천문학회 2019 Journal of The Korean Astronomical Society Vol.52 No.1
The KVN(Korean VLBI Network)-style simultaneous multi-frequency receiving mode is demonstrated to be promising for mm-VLBI observations. Recently, other Very long baseline interferometry (VLBI) facilities all over the globe start to implement compatible optics systems. Simultaneous dual/multi-frequency VLBI observations at mm wavelengths with international baselines are thus possible. In this paper, we present the results from the first successful simultaneous 22/43 GHz dualfrequency observation with KaVA(KVN and VERA array), including images and astrometric results. Our analysis shows that the newly implemented simultaneous receiving system has brought a significant extension of the coherence time of the 43 GHz visibility phases along the international baselines. The astrometric results obtained with KaVA are consistent with those obtained with the independent analysis of the KVN data. Our results thus confirm the good performance of the simultaneous receiving systems for the non-KVN stations. Future simultaneous observations with more global stations bring even higher sensitivity and micro-arcsecond level astrometric measurements of the targets.