Browsing by Author "Cao, Tianwen"

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    ALMA Observation of NGC 5135: The Circumnuclear CO (6-5) and Dust Continuum Emission at 45 pc Resolution
    (2018) Cao, Tianwen; Lu, Nanyao; Xu, C. Kevin; Zhao, Yinghe; Madhav Kalari, Venu; Gao, Yu; Charmandaris, Vassilis; Diaz Santos, Tanio; Van der Werf, Paul; Cao, Chen; Wu, Hong; Inami, Hanae; Evans, Aaron S.
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    CO (7-6), [C I] 370 mu m, and [N II] 205 mu m Line Emission of the QSO BRI1335-0417 at Redshift 4.407
    (2018) Lu, Nanyao; Cao, Tianwen; Diaz-Santos, Tanio; Zhao, Yinghe; Privon, George C.; Cheng, Cheng; Gao, Yu; Xu, C. Kevin; Charmandaris, Vassilis; Rigopoulou, Dimitra; Van der Werf, Paul P.; Huang, Jiasheng; Wang, Zhong; Evans, Aaron S.; Sanders, David B.
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    Intrinsic Morphology of Ultra-diffuse Galaxies
    (IOP PUBLISHING LTD, 2020) Rong, Yu; Dong, Xiao Yu; Puzia, Thomas H.; Galaz, Gaspar; Sanchez Janssen, Ruben; Cao, Tianwen; van der Burg, Remco F. J.; Sifon, Cristobal; Pina, Pavel E. Mancera; Marcelo, Mora; D'Ago, Giuseppe; Zhang, Hong Xin; Johnston, Evelyn J.; Eigenthaler, Paul
    With the published data of apparent axis ratios for 1109 ultra-diffuse galaxies (UDGs) located in 17 low-redshift (z similar to 0.020-0.063) galaxy clusters and 84 UDGs in two intermediate-redshift (z similar to 0.308-0.348) clusters, we take advantage of a Markov Chain Monte Carlo approach and assume a triaxial model to investigate the intrinsic morphologies of UDGs. In contrast to the conclusion of Burkert, i.e., the underlying shapes of UDGs are purely prolate (C = B < A), we find that the data favor the oblate-triaxial models (i.e., thick disks with C < B less than or similar to A) over the nearly prolate ones. We also find that the intrinsic morphologies of UDGs are related to their stellar masses/luminosities, environments, and redshifts. First, the more luminous UDGs have puffier morphologies compared with the less luminous counterparts; the UDG morphologic dependence on luminosity is distinct from that of the typical quiescent dwarf ellipticals (dEs) and dwarf spheroidals (dSphs); in this sense, UDGs may not be simply treated as an extension of the dE/dSph class with similar evolutionary histories; they may differ not only in size. Second, the UDGs with smaller clustercentric distances are more puffed up, compared with the counterparts with larger clustercentric distances; in combination with the UDG thickness dependence on luminosity, the puffier morphologies of UDGs with high luminosities or located in the denser environments are very likely to be attributed to tidal interactions with massive galaxies. Third, we find that the intermediate-redshift UDGs are more flattened, compared with the low-redshift counterparts, which plausibly suggests a "disky" origin for the high-redshift, newly born UDGs.
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    Lessons on Star-forming Ultra-diffuse Galaxies from the Stacked Spectra of the Sloan Digital Sky Survey
    (2020) Rong, Yu; Zhu, Kai; Johnston, Evelyn J.; Zhang, Hong-Xin; Cao, Tianwen; Puzia, Thomas H.; Galaz, Gaspar
    We investigate the on-average properties for 28 star-forming ultra-diffuse galaxies (UDGs) located in low-density environments, by stacking their spectra from the Sloan Digital Sky Survey. These relatively isolated UDGs, with stellar masses of log(10) (M-*/M-circle dot) similar to 8.57 +/- 0.29, have the on-average total stellar metallicity [M/H] similar to -0.82 +/- 0.14, iron metallicity [Fe/H] similar to -1.00 +/- 0.16, stellar age t(*) similar to 5.2 +/- 0.5 Gyr, alpha-enhancement [alpha/Fe] similar to 0.24 +/- 0.10, and oxygen abundance 12+log(O/H) similar to 8.16 +/- 0.06, as well as central stellar velocity dispersion 54 +/- 12 km s(-1). On the star formation rate versus stellar mass diagram, these UDGs are located lower than the extrapolated star-forming main sequence from the massive spirals, but roughly follow the main sequence of low-surface-brightness dwarf galaxies. We find that these star-forming UDGs are not particularly metal-poor or metal-rich for their stellar masses, as compared with the metallicity-mass relations of the nearby typical dwarfs. With the UDG data of this work and previous studies, we also find a coarse correlation between [Fe/H] and magnesium-element enhancement [Mg/Fe] for UDGs: [Mg/Fe] similar or equal to -0.43(+/- 0.26) [Fe/H] -0.14(+/- 0.40).