Delectability of Massive Tori in Proto-QSOs with ALMA

Abstract

We examine the detectability of ∼100 pc scale massive tori with 108−9M with the Atacama Large Millimeter Array (ALMA). Such massive tori are predicted to lie in the centre of elliptical galaxy progenitors by a model of a supermassive black hole growth coeval to the spheroidal population of the host galaxy [1]. We propose that submillimeter galaxies (SMGs) are the best targets to test our predictions. In order to assess the observational feasibility, we estimate the expected number counts of SMGs with massive tori and check the detectability with the ALMA instrument, the unique facility which can resolve the central region of high redshift objects. Our work shows that ALMA will be able to resolve and detect high-J (J > 4) CO emissions from massive tori up to z ≈ 2 at 5σ in twelve hours on-source integration time and a velocity resolution of 25 km/s (please see our poster). In addition, we predict the number count of SMGs with a massive torus (more than 10M ) ≈ 100 deg−2 at the redshift 1 < z < 3. We stress the relevance of studying with ALMA samples of gravitationally lensed SMGs. It can allow a much higher spatial resolution, which can be a crucial piece of information in inferring the gas distribution in the very central regions around the growing SMBHs. Moreover, it is worth to discuss the possible detection of molecular clouds along the line of sight – associated with .. – not belonging to the massive central torus. CO lines in massive tori have likely very large velocity width (a few hundreds of km/s) because of their rotation around the central BH. Normal molecular clouds in star-forming region can move randomly with much less than 100 km/s.Velocity mapping is therefore the crucial observational tool to distinguish among the two cases (Kawakatu et al. 2006 in preparation).