About Me

Currently working with Rob Ivison at both the University of Edinburgh and ESO , as a postdoc fellow. Working on the project COSMICISM. Got my Ph.D. degree in Purple Mountain Observatory (PMO) , Nanjing, China, supervised by Yu Gao in the SFIG group of PMO, and Christian Henkel in the Max Planck Institute for Radio Astronomy (MPIfR) .

Specialised in observational radio astronomy and physical conditions of interstellar medium. Currently working on the impact of the Cosmic Microwave Background to mm/sub-mm observations of galaxies in the early Universe. Especially interested in the physical connection between dense molecular gas (traced by CS, HCN, HCO+, high-J CO, etc.), star formation and its feedback in galaxies near and far. Working on models to derive the excitation physical conditions from multiple molecular transitions and multiple species. Interaction between supernova remnants and molecular clouds is also what I am interested in.

Experienced in observations using radio/mm/sub-mm telescopes (both single dish and interferometers), including Arecibo, GBT, Effelsberg, IRAM 30m, PMO 14m, MOPRA, ARO 12m, CSO, (HH)SMT, APEX, (J)VLA, ALMA, etc.


Here please find my publications: Publication

Contact Details

ESO E.401
Karl Schwarzschild Straße 2, D-85748 Garching, Munich, Germany
@ z ~ 0
zzhang AT eso DOT org

Tel: +49-89-3200-6910

My Research

A fundamental constraint of imaging cold ISM in the early Universe set by the CMB -- You don’t see it, and now you do: Galaxies coming out from the cold

We have found that the afterglow of the Big Bang, the so called Cosmic Microwave Background (CMB), can seriously frustrate our efforts to image the cold hydrogen gas molecules and cosmic dust found in galaxies in the distant Universe. These large amounts of the so-called Interstellar Medium (ISM) is where stars eventually form (and where our own Sun and Solar System was born nearly 4.5 billion years ago). Mapping these huge clouds of cold hydrogen gas and cosmic dust is to know where the next generation of stars will form in faraway galaxies. Yet, as the CMB background becomes warmer and warmer in the distant Universe, its temperature become almost equal to those emitted by the cold, optically-dark, interstellar medium in galaxies. This effect makes such interstellar medium nearly invisible against the rising glow of a warmer CMB. The effect makes it very hard to detect where new stars will form in distant galaxies. It would be like trying to see a swan in the snow, or the shrinking of an ocean island in a rising tide.

This would have been bad news for the two largest radio telescopes on Earth, the newly commissioned Atacama Large Millimeter Array (ALMA), and the Jansky Very Large Array (JVLA). This is because part of their purpose is to find where such cold, optically-dark, and eventually star-forming gas and dust exist in the distant Universe. Yet, in a hopeful twist, we found that at high enough frequencies these massive cold clouds become again much brighter than the CMB. ALMA can 'tune' to such high frequencies. This will eventually recover the information carried by the exceedingly faint radio waves from the cold interstellar medium, to be detected and deciphered, well above the ever-present noise of the Big Bang.