Outflows and Bubbles in Taurus: Star-formation Feedback Sufficient to Maintain Turbulence

We have identified outflows and bubbles in the Taurus molecular cloud based on the ~100 deg^2 Five College Radio Astronomy Observatory ^(12)CO(1-0) and ^(13)CO(1-0) maps and the Spitzer young stellar object catalogs. In the main 44 deg^2 area of Taurus, we found 55 outflows, of which 31 were previously unknown. We also found 37 bubbles in the entire 100 deg^2 area of Taurus, none of which had been found previously. The total kinetic energy of the identified outflows is estimated to be ~3.9 x 10^(45) erg, which is 1% of the cloud turbulent energy. The total kinetic energy of the detected bubbles is estimated to be ~9.2 x 10^(46) erg, which is 29% of the turbulent energy of Taurus. The energy injection rate from the outflows is ~1.3 x 10^(33) erg s^(-1), which is 0.4–2 times the dissipation rate of the cloud turbulence. The energy injection rate from bubbles is ~6.4 x 10^(33) erg s^(−1), which is 2–10 times the turbulent dissipation rate of the cloud. The gravitational binding energy of the cloud is ~1.5 x 10^(48) erg, that is, 385 and 16 times the energy of outflows and bubbles, respectively. We conclude that neither outflows nor bubbles can provide sufficient energy to balance the overall gravitational binding energy and the turbulent energy of Taurus. However, in the current epoch, stellar feedback is sufficient to maintain the observed turbulence in Taurus

GMRT detection of HI 21 cm associated absorption towards the z=1.2 red quasar 3C 190

We report the GMRT detection of associated HI 21 cm-line absorption in the z=1.1946 red quasar 3C 190. Most of the absorption is blue-shifted with respect to the systemic redshift. The absorption, at $\sim$ 647.7 MHz, is broad and complex, spanning a velocity width of $\sim$ 600 \kms. Since the core is self-absorbed at this frequency, the absorption is most likely towards the hotspots. Comparison of the radio and deep optical images reveal linear filaments in the optical which overlap with the brighter radio jet towards the south-west. We therefore suggest that most of the HI 21 cm-line absorption could be occurring in the atomic gas shocked by the south-west jet.Comment: 8 pages, 1 fugure. To appear in Journal of Astrophysics and Astronom

SKA Survey Optimization

images with superb image quality, which imposes stringent requirements on the calibration and sidelobe levels at every stage of beam formation. The cost of data processing is very dependent on the antenna system, calibration, and data processing paradigm. The optimal design of the SKA must consider the overall system from the science goals to the data products. In this memo we explore performance and cost criteria which recognize the interaction of different subsystems for survey science. We use as a reference design an array of small diameter antennas with focal plane phased array feeds from 300 MHz to 3 GHz and wide band single pixel feeds at higher frequencies. The survey speed ∼ Nbeams × λ 2 × (ND/T) 2 × BW, where N is the number of antennas, D is the antenna diameter and T the system temperature. The cost of the SKA is dominated by four major components: antennas, receivers, signal processing, and computing. Each has strong interdependencies, and must be optimized in the context of the overall science and engineering goals. For the highest dynamic range the calibration implicit in beamforming with FPA or station beams must be redone in the data analysis, leading to a large increase in computing costs. 1