Here is the list of the previous and ongoing research projects I am involved in:

  1. 2017, Molecular gas in the Herschel-selected strongly lensed submillimeter galaxies at z ∼ 2–4 as probed by multi-J CO lines

    C. Yang, A. Omont, A. Beelen, Y. Gao, P. van der Werf, R. Gavazzi, Z.-Y. Zhang, R. Ivison, M. Lehnert, D. Liu, I. Oteo, E. Gonzàlez-Alfonso, H. Dannerbauer, P. Cox, M. Krips, R. Neri, D. Riechers, A. J. Baker, M.J. Michałowski, A. Cooray and I. Smail

    from Yang et
                 al. 2017
    Fig.1  The distribution of the observed velocity-integrated CO line flux density versus the rotational quantum number Jup for each transition, i.e. CO SLEDs. Black dots with error bars are the velocity integrated flux densities from this work. Red dots are the data from other works.


    from Yang et
                 al. 2017
    Fig.2  Modelling LVG results via a MCMC approach (emcee). Upper left panel: The CO SLED of each source is plotted in black. The solid orange curve shows the best fit from the single component model corresponding to the maximum posterior possibility, while the solid purple line shows the best fit of the two-component model. Dashed red line shows the warmer component and the dashed-dotted line shows the cooler component fit. The upper limits are shown in grey open circles with downward arrows. Upper right panel: The posterior probability distributions of molecular gas density nH2 , gas temperature Tkin and CO column density per velocity NCO/dv of the source, with the maximum posterior possibility point in the parameter space shown in orange lines and points. The contours are in steps of 0.5 σ starting from the centre. Lower panels: The posterior probability distributions for nH2 , Tkin and NCO/dv of the cooler (dark green) and warmer (light green) component of the two-component model.
    from Yang et
                 al. 2017
    Fig.3  The CO SLEDs of local galaxies and high-redshift SMGs normalised by total infrared luminosity. Grey symbols indicate the Gaussian mean of local infrared bright galaxies (without ULIRGs). We also include a typical local ULIRG, Arp 220 (purple dashed line and open triangles), an AGN-dominated source, Mrk 231 (red dashed line and open diamond), and a LIRG, NGC7771 (green dashed line and open square). Red symbols show high-redshift SMGs. It is clear that the CO SLED decreases with increasing Jup for local galaxies while it remains flat for high-redshift SMGs and typical starburst-dominated ULIRGs, such as Arp 220.


    from Yang et
                 al. 2017
    Fig.4  Left: Thermal gas pressure plotted against star formation efficiency. Filled circles are the H-ATLAS SMGs. We also plot the values of the Milky Way, the Tuffy galaxies, the Antennae galaxies, Arp 220 and HFLS3 in filled triangles for comparison. The colour is coded based on their values of molecular gas density. The red line shows the fit to the correlation, which yields a slope of 1.1±0.5 for all the sources. The grey dashed square shows the region where H-ATLAS SMGs reside. Middle: Similar correlation plot as in the left panel but only for the cool component from the two-component LVG modelling. There is no correlation found. Right: Similar correlation plot as in the left panel but only for the warm component in the two-component LVG modelling. The dashed red line is an overlay of exactly the same red line plotted in the left panel. The data points follow the same correlation found in the single component fit. In all the three panels, the legends show the Pearson’s correlation coefficient RP with corresponding p-value. The values of nH2 for each point are indicated by the colour bar.


    Publication: C. Yang, A. Omont, A. Beelen, Y. Gao, P. van der Werf, R. Gavazzi, et al., 2017, A&A, 608, A144;
    >>(arXiv:1709.04740)<<
  2. 2016, Submillimeter H2O and H2O+ emission in lensed ultra- and hyper-luminous infrared galaxies at z~2-4
    from Yang et
                 al. 2016
    Fig.1  Correlation between LIR and Lwater in local ULIRGs and high-redshift Hy/ULIRGs. The black points represent local ULIRGs from Yang et al. 2013. The blue points with solid error bars are the H-ATLAS source in this work together with some previously published sources. Red points with dashed error bars are excluded from the fit as described in the text. Upper limits are shown in arrows. The light blue lines show the results of the fitting. The insets are the probability density distributions of the fitted slopes α.


    from Yang et
                 al. 2016
    Fig.2  Parameter space distribution of the H2O far-infrared pumping excitation modelling with observed para-H2O 202–111 or 211–202 and ortho- H2O(321–312) in each panel. ±1σ contours are shown for each plot. Different colours with different line styles represent different temperature components of the warm dust as shown in the legend. The explored warm dust temperature range is from 35 K to 115 K. The temperature contours that are unable to fit the data are not shown in this figure. From the figure, we are able to constrain the τ100, Twarm and NH2O/∆V for the five sources. However, there are strong degeneracies. Thus, we need additional information, such as the velocity-integrated flux densities of J ≥ 4 H2O lines, to better constrain the physical parameters.


    from Yang et
                 al. 2016
    Fig.3 Correlation between the luminosity of J = 2 ortho-H2O+ and para-H2O(211–202). The fitted function is LH2O+LH2Oα. We found a very good correlation between LH2O+ and LH2O with a slope close to one. Black points are from the local ULIRGs as listed in the table in the appendix of the paper. Dark blue ones are high-redshift starbursts from this work. Black solid lines indicate the χ2 fitting results while the grey dashed lines and the grey annotations represent the average ratio between the LH2O+ and LH2O.


    Publication:
    C. Yang, A. Omont, A. Beelen, E. González-Alfonso, R. Neri, Y. Gao, P. van der Werf, A. Weiß, R. Gavazzi, N. Falstad, et al., 2016, A&A 595, A80;
    >>(arXiv:1607.06220)<<
  3. 2013, Water vapor in nearby infrared galaxies as probed by Herschel
    IAUS315 Poster (Poster PDF).
    Supervision: Yu Gao (PMO, CN)

    from Atkins physical
                  chemistry, Chapter 13
    Fig.1 The figure left shows H2O molecule and its rotation axes (Credit: Atkins' Physical Chemistry, 9th Edition). The H2O emission lines we observed are within the submillimeter (submm) frequency window, and you can see the J, Ka and Kc (e.g., 111-000, 202-111, 211-202, 220-211, 312-303, 321-312, 422-413 and 523-514) in the right figure (blue arrows). Red arrows indicate the possible infrared pumping paths, with the wavelength of three main pumping paths. These submm H2O lines are the second strongest after CO emission lines (within similar frequency range), even comparable in some cases.


    from ApJ,
                  771, L24
    Fig.2 A tight correlation between submm H2O line and total IR luminosities.

    from ApJ, 771,
                  L24
    Fig.3 Normalized SLED of submm H2O lines shows two peaks at low- and high-lying transitions respectively.

    Publication:
    Chentao Yang, Yu Gao, A. Omont, Daizhong Liu et al., Water vapor in nearby infrared galaxies as probed by Herschel, 2013, ApJ, 771, L24;
    >>(arXiv:1305.6351)<<
    Informations of the samples in the paper: TABLE
    The submm water line luminosities and the beam-matched IR luminosities: TABLE
  4. 2013, H2 O emission in high-z ultra-luminous infrared galaxies
    PI: Alain Omont (IAP, FR)

    from Omont et
                   al., 2013
    Fig.1 Similar line profiles of H2O and CO hinting similar physical conditions.

    from Omont et
                  al., 2013
    Fig.2 Images of the submillimeter continuum (left panel) and H2O line emission (right panel, see Fig. 1 for the transitions).


    Publication:
    A. Omont, C. Yang, P. Cox, R. Neri, et al., 2013, H2O emission in high-z ultra-luminous infrared galaxies, 2013, A&A, 551, A115;
    >>(arXiv:1301.6618)<<
  5. On-going, Resolving CO and H2O emission in a strongly lensed starburst galaxy at z = 3.6 with kiloparsec-scale ALMA imaging;


    Publication: in prep.
  6. On-going, Exploring dense molecular gas properties in two lensed Herschel galaxies at z~3.6


    Publication: in prep.