Browsing by Subject "PHYSICAL CONDITIONS"

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  • Tatematsu, Ken'ichi; Liu, Tie; Ohashi, Satoshi; Sanhueza, Patricio; Quang Nguyen Luong,; Hirota, Tomoya; Liu, Sheng-Yuan; Hirano, Naomi; Choi, Minho; Kang, Miju; Thompson, Mark A.; Fuller, Gary; Wu, Yuefang; Li, Di; Di Francesco, James; Kim, Kee-Tae; Wang, Ke; Ristorcelli, Isabelle; Juvela, Mika; Shinnaga, Hiroko; Cunningham, Maria; Saito, Masao; Lee, Jeong-Eun; Toth, L. Viktor; He, Jinhua; Sakai, Takeshi; Kim, Jungha; JCMT Large Program SCOPE Collabora; TRAO Key Science Program TOP Colla (2017)
    We observed 13 Planck cold clumps with the James Clerk Maxwell Telescope/SCUBA-2 and with the Nobeyama 45 m radio telescope. The N2H+ distribution obtained with the Nobeyama telescope is quite similar to SCUBA-2 dust distribution. The 82 GHz HC3N, 82 GHz CCS, and 94 GHz CCS emission are often distributed differently with respect to the N2H+ emission. The CCS emission, which is known to be abundant in starless molecular cloud cores, is often very clumpy in the observed targets. We made deep single-pointing observations in DNC, (HNC)-C-13, N2D+, and cyclic-C3H2 toward nine clumps. The detection rate of N2D+ is 50%. Furthermore, we observed the NH3 emission toward 15 Planck cold clumps to estimate the kinetic temperature, and confirmed that most targets are cold (less than or similar to 20 K). In two of the starless clumps we observed, the CCS emission is distributed as it surrounds the N2H+ core (chemically evolved gas), which resembles the case of L1544, a prestellar core showing collapse. In addition, we detected both DNC and N2D+. These two clumps are most likely on the verge of star formation. We introduce the chemical evolution factor (CEF) for starless cores to describe the chemical evolutionary stage, and analyze the observed Planck cold clumps.
  • Ahoranta, Jussi; Nevalainen, Jukka; Wijers, Nastasha; Finoguenov, Alexis; Bonamente, Massilimiano; Tempel, Elmo; Tilton, Evan; Schaye, Joop; Kaastra, Jelle; Gozaliasl, Ghassem (2020)
    Aims. We explore the high spectral resolution X-ray data towards the quasar 3C 273 to search for signals of hot (similar to 10^(6-7) K) X-ray-absorbing gas co-located with two established intergalactic far-ultraviolet (FUV) OVI absorbers. Methods. We analyze the soft X-ray band grating data of all XMM-Newton and Chandra instruments to search for the hot phase absorption lines at the FUV predicted redshifts. The viability of potential line detections is examined by adopting the constraints of a physically justified absorption model. The WHIM hypothesis is investigated with a complementary 3D galaxy distribution analysis and by detailed comparison of the measurement results to the WHIM properties in the EAGLE cosmological, hydrodynamical simulation. Results. At one of the examined FUV redshifts, 0.09017 +/- 0.00003, we measured signals of two hot ion species, ;VIII and x202f;IX, with a 3.9 sigma combined significance level. While the absorption signal is only marginally detected in individual co-added spectra, considering the line features in all instruments collectively and assuming collisional equilibrium for absorbing gas, we were able to constrain the temperature (kT = 0.26 +/- 0.03 keV) and the column density cm(-2)) of the absorber. Thermal analysis indicates that FUV and X-ray absorption relate to different phases, with estimated temperatures, T-FUV & x2004;3 x 10(5), and, T(X - ray)x2004;3 x 10(6) K. These temperatures match the EAGLE predictions for WHIM at the FUV/X-ray measured N-ion-ranges. We detected a large scale galactic filament crossing the sight-line at the redshift of the absorption, linking the absorption to this structure. Conclusions. This study provides observational insights into co-existing warm and hot gas within a WHIM filament and estimates the ratio of the hot and warm phases. Because the hot phase is thermally distinct from the OVI gas, the estimated baryon content of the absorber is increased, conveying the promise of X-ray follow-up studies of FUV detected WHIM in refining the picture of the missing baryons.
  • Zhang, Chuan-Peng; Liu, Tie; Yuan, Jinghua; Sanhueza, Patricio; Traficante, Alessio; Li, Guang-Xing; Li, Di; Tatematsu, Ken'ichi; Wang, Ke; Lee, Chang Won; Samal, Manash R.; Eden, David; Marston, Anthony; Liu, Xiao-Lan; Zhou, Jian-Jun; Li, Pak Shing; Koch, Patrick M.; Xu, Jin-Long; Wu, Yuefang; Juvela, Mika; Zhang, Tianwei; Alina, Dana; Goldsmith, Paul F.; Toth, L.; Wang, Jun-Jie; Kim, Kee-Tae (2018)
    In order to understand the initial conditions and early evolution of star formation in a wide range of Galactic environments, we carried out an investigation of 64 Planck Galactic cold clumps (PGCCs) in the second quadrant of the Milky Way. Using the (CO)-C-13 and (CO)-O-18 J = 1-0 lines and 850 mu m continuum observations, we investigated cloud fragmentation and evolution associated with star formation. We extracted 468 clumps and 117 cores from the (CO)-C-13 line and 850 mu m continuum maps, respectively. We made use of the Bayesian distance calculator and derived the distances of all 64 PGCCs. We found that in general, the mass-size plane follows a relation of m similar to r(1.67). At a given scale, the masses of our objects are around 1/10 of that of typical Galactic massive star-forming regions. Analysis of the clump and core masses, virial parameters, densities, and mass-size relation suggests that the PGCCs in our sample have a low core formation efficiency (similar to 3.0%), and most PGCCs are likely low-mass star-forming candidates. Statistical study indicates that the 850 mu m cores are more turbulent, more optically thick, and denser than the (CO)-C-13 clumps for star formation candidates, suggesting that the 850 mu m cores are likely more appropriate future star formation candidates than the (CO)-C-13 clumps.