0910.1609 (J. Di Francesco et al.)

The Science Case for Building a Band 1 Receiver Suite for ALMA    [PDF]

J. Di Francesco, D. Johnstone, B. Matthews, N. Bartel, L. Bronfman, S. Casassus, S. Chitsazzadeh, M. Cunningham, G. Duchene, A. Hales, M. Houde, D. Iono, P. M. Koch, R. Kothes, S. -P. Lai, S. -Y. Liu, B. Mason, T. Maccarone, G. Schieven, A. M. M. Scaife, D. Scott, H. Shang, S. Takakuwa, J. Wagg, A. Wootten, F. Yusef-Zadeh

We present a set of compelling science cases for the ALMA Band 1 receiver suite. For these cases, we assume in tandem the updated nominal Band 1 frequency range of 35-50 GHz with a likely extension up to 52 GHz; together these frequencies optimize the Band 1 science return. The scope of the science cases ranges from nearby stars to the re-ionization edge of the Universe. Two cases provide additional leverage on the present ALMA Level One Science Goals and are seen as particularly powerful motivations for building the Band 1 Receiver suite: (1) detailing the evolution of grains in protoplanetary disks, as a complement to the gas kinematics, requires continuum observations out to ~35 GHz (~9mm); and (2) detecting CO 3-2 line emission from galaxies like the Milky Way during the epoch of re-ionization, i.e., 6 < z < 10, also requires Band 1 receiver coverage. The range of Band 1 science is wide, however, and includes studies of very small dust grains in the ISM, pulsar wind nebulae, radio supernovae, X-ray binaries, the Galactic Center (i.e., Sgr A*), dense cloud cores, complex carbon-chain molecules, masers, magnetic fields in the dense ISM, jets and outflows from young stars, distant galaxies, and galaxy clusters (i.e., the Sunyaev-Zel'dovich Effect). A comparison of ALMA and the Jansky VLA (JVLA) at the same frequencies of Band 1 finds similar sensitivity performance at 40-50 GHz, with a slight edge for ALMA at higher frequencies (e.g., within a factor of 2 for continuum observations). With its larger number of instantaneous baselines, however, ALMA Band 1data will have greater fidelity than those from the JVLA at similar frequencies.

View original: http://arxiv.org/abs/0910.1609