Limits on galaxy evolution

Galaxy Evolution

Telescope limits on cool H I in galaxy groups

We present Giant Metrewave Radio Telescope 21-cm HI observations towards a sample of compact radio sources behind galaxy groups, to search for cool HI. The results – from high dynamic range spectra for 8 lines-of-sight through 7 galaxy groups – do not show any evidence for absorption by cool HI. At a resolution of 20 km s −1 , the optical depth upper limits obtained were between 0.0075 and 0.03...

Stellar-Evolution Limits on Axion Properties

If axions exist, they are copiously produced in hot and dense plasmas, carrying away energy directly from the interior of stars. Various astronomical observables constrain the operation of such anomalous stellar energy-loss channels and thus provide restrictive limits on the axion interactions with photons, nucleons, and electrons. In typical axion models a limit ma < ∼ 10 eV is implied. The ma...

Galaxy Formation and Evolution

Galaxy Evolution with Alma

The submillimeter and millimeter domains are privileged for the exploration of galaxies at high redshift, because of the negative K-correction: the peak of the dust emission at 60-100 microns is red-shifted in these domains. Already blind surveys in blank fields with today instrumentation have discovered in the continuum of the order of one object per square arcmin, with large limitations due t...