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Planck Cold Clumps in the <i>λ</i> Orionis Complex. II. Environmental Effects on Core Formation
Yi, Hee-Weon,Lee, Jeong-Eun,Liu, Tie,Kim, Kee-Tae,Choi, Minho,Eden, David,II, Neal J. Evans,Francesco, James Di,Fuller, Gary,Hirano, N.,Juvela, Mika,Kang, Sung-ju,Kim, Gwanjeong,M. Koch, Patrick,Lee, American Astronomical Society 2018 The Astrophysical journal, Supplement series Vol.236 No.2
<P>Based on the 850 mu m dust continuum data from SCUBA-2 at James Clerk Maxwell Telescope (JCMT), we compare overall properties of Planck Galactic Cold Clumps (PGCCs) in the lambda Orionis cloud to those of PGCCs in the Orion A and B clouds. The Orion A and B clouds are well-known active star-forming regions, while the A Orionis cloud has a different environment as a consequence of the interaction with a prominent OB association and a giant H-II region. PGCCs in the lambda Orionis cloud have higher dust temperatures (T-d = 16.13 +/- 0.15 K) and lower values of dust emissivity spectral index (beta = 1.65 +/- 0.02) than PGCCs in the Orion A (T-d = 13.79 +/- 0.21 K, beta = 2.07 +/- 0.03) and Orion B (T-d = 13.82 +/- 0.19 K, beta =1.96 +/- 0.02) clouds. We find 119 substructures within the 40 detected PGCCs and identify them as cores. Out of a total of 119 cores, 15 cores are discovered in the lambda Orionis cloud, while 74 and 30 cores are found in the Orion A and B clouds, respectively. The cores in the lambda Orionis cloud show much lower mean values of size R = 0.08 pc, column density N(H-2) (9.5 +/- 1.2) x 10(22)cm(-2) , number density n(H-2) - (2.9 +/- 0.4) x 10 5 CM -3 , and mass M-core = 1.0 +/- 0.3 M(circle dot)compared to the cores in the Orion A [R = 0.11 pc, N(H-2) = (2.3 +/- 0.3) x 10(23) cm(-2), n(H-2) = (3.8 +/- 0.5) x 10(5)cm(-3) , and M-core = 2.4 +/- 0.3 M-circle dot] and Orion B [R = 0.16 pc, N(H-2) (3.8 +/- 0.4) x 10(23) cm(-2), n(H-2) = (15.6 +/- 1.8) x 10(5) cm(-3) , and M-core = 2.7 +/- 0.3 M-circle dot] clouds. These core properties in the A Orionis cloud can be attributed to the photodissociation and external heating by the nearby H rr region, which may prevent the PGCCs from forming gravitationally bound structures and eventually disperse them. These results support the idea of negative stellar feedback on core formation.</P>
Size-dependent vibronic coupling in α-Fe<sub>2</sub>O<sub>3</sub>
O'Neal, K. R.,Patete, J. M.,Chen, P.,Holinsworth, B. S.,Smith, J. M.,Lee, N.,Cheong, S.-W.,Wong, Stanislaus S.,Marques, C.,Aronson, M. C.,Musfeldt, J. L. American Institute of Physics 2014 The Journal of chemical physics Vol.141 No.4
<P>We report the discovery of finite length scale effects on vibronic coupling in nanoscale alpha-Fe2O3 as measured by the behavior of vibronically activated d-d on-site excitations of Fe3+ as a function of size and shape. An oscillator strength analysis reveals that the frequency of the coupled symmetry-breaking phonon changes with size, a crossover that we analyze in terms of increasing three-dimensional character to the displacement pattern. These findings demonstrate the flexibility of mixing processes in confined systems and suggest a strategy for both enhancing and controlling charge-lattice interactions in other materials. (C) 2014 AIP Publishing LLC.</P>
Magnetoelectric Coupling through the Spin Flop Transition in<sub>Ni3</sub><sub>TeO6</sub>
Yokosuk, M. O.,al-Wahish, Amal,Artyukhin, Sergey,O’Neal, K. R.,Mazumdar, D.,Chen, P.,Yang, Junjie,Oh, Yoon Seok,McGill, Stephen A.,Haule, K.,Cheong, Sang-Wook,Vanderbilt, David,Musfeldt, J. L. American Physical Society 2016 Physical Review Letters Vol.117 No.14
EVIDENCES OF EPISODIC MASS ACCRETION IN LOW-LUMINOSITY EMBEDDED PROTOSTARS
Kim, Hyo Jeong,Evans, Neal J. II,Dunham, Michael M.,Lee, Jeong-Eun,Pontoppidan, Klaus M. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
We present Spitzer IRS spectroscopy of $CO_2$ ice toward 19 young stellar objects (YSOs) with luminosity lower than $1L_{\odot}$. Pure $CO_2$ ice forms only at elevated temperatures, T > 20 K, and thus at higher luminosities. Current internal luminosities of YSOs with L < $1L_{\odot}$ do not provide such conditions out to radii of typical envelopes. Significant amounts of pure $CO_2$ ice would signify a higher past luminosity. We analyze $15.2{\mu}m$ $CO_2$ ice bending mode absorption lines in comparison to the laboratory data. We decompose pure $CO_2$ ice from 12 out of 19 young low luminosity sources. The presence of the pure $CO_2$ ice component indicates high dust temperature and hence high luminosity in the past. The sum of all the ice components (total $CO_2$ ice amount) can be explained by a long period of low luminosity stage between episodic accretion bursts as predicted in an episodic accretion scenario. Chemical modeling shows that the episodic accretion scenario explains the observed total $CO_2$ ice amount best.
Jang, H.,Kim, K.,Neal, Scott J.,Macosko, E.,Kim, D.,Butcher, Rebecca A.,Zeiger, Danna M.,Bargmann, Cornelia I.,Sengupta, P. Cell Press 2012 Neuron Vol.75 No.4
Pheromone responses are highly context dependent. For example, the C. elegans pheromone ascaroside C9 (ascr#3) is repulsive to wild-type hermaphrodites, attractive to wild-type males, and usually neutral to ''social'' hermaphrodites with reduced activity of the npr-1 neuropeptide receptor gene. We show here that these distinct behavioral responses arise from overlapping push-pull circuits driven by two classes of pheromone-sensing neurons. The ADL sensory neurons detect C9 and, in wild-type hermaphrodites, drive C9 repulsion through their chemical synapses. In npr-1 mutant hermaphrodites, C9 repulsion is reduced by the recruitment of a gap junction circuit that antagonizes ADL chemical synapses. In males, ADL sensory responses are diminished; in addition, a second pheromone-sensing neuron, ASK, antagonizes C9 repulsion. The additive effects of these antagonistic circuit elements generate attractive, repulsive, or neutral pheromone responses. Neuronal modulation by circuit state and sex, and flexibility in synaptic output pathways, may permit small circuits to maximize their adaptive behavioral outputs.