TWHydraBand7 For CASA 3.3

Science Target Overview

SMA CO(3-2) emission from TW Hya (Hughes et al. 2011).

TW Hya is a pre-main sequence classical T Tauri star at a distance of about 52+/-1 pc (Mamajek 2005,2010). TW Hya is the most studied member of the TW Hydra association (TWA) of low mass stars. From a wide variety of previous observations from the infrared to submillimeter, TW Hya is known to have a small optically thin hot inner disk to radii < 4 AU, and a larger cold dust disk out to about 200 AU (see for example introduction by Vacca & Sandell 2011, and references therein). Recent optical interferometry finds that TW Hya also contains a hot optically thick disk on even smaller sizescales of ~0.5 AU, and suggests that the optically thin disk could be due to gas clearing by a planet (Akeson et al. 2011). TW Hya is still accreting from its disk at a rate of about (4-20) x 10^-10 Msun/year and most recently its spectral type, mass, and age have been estimated at M2.5V, 0.4 Msun, and 3 Myr (Vacca & Sandell 2011).

Millimeter and submillimeter observations of the continuum and spectral lines are particularly useful for tracing in the outer cold disk. Previous observations by the VLA at 7 mm (Wilner et al. 2000), ATCA at 3 mm (Wilner et al. 2003), and the SMA at 1.3, 0.87, and 0.45 mm (Qi et al. 2004, 2006, 2008 and Hughes et al. 2011) reveal Keplerian rotation in the disk and an inclination of about 7 degrees (i.e. almost face-on). Detailed studies of the dust continuum properties from this work suggests that there are centimeter sized particles within the cold protoplanetary disk.

Data Overview

ALMA Science Verification data at Band 7 (~345 GHz) was taken for TW Hya on April 22, 2011. All four available basebands were used, resulting in four spectral windows (spws) containing data. Two basebands were placed in the Lower Sideband (LSB) and two basebands in the Upper Sideband (USB). In the LSB the CO(3-2) line at a rest frequency of 345.79599 GHz is located in spw=2. In the USB the HCO+(4-3) line at a rest frequency of 356.7342 GHz is located in spw=0. The other two spectral windows do not contain detectable spectral lines and are used for continuum. Each spectral window is 0.5 GHz wide and the channel width is 122 kHz.

For Science Verification purposes the CO(3-2) data is similar to the Submillimeter Array data presented in Hughes et al. 2011 (ApJ, 727, 85), though the SMA data has ~3 times smaller channel with at 50 kHz.

HCO+(4-3) SMA data has not previously been published, but HCO+(3-2) data (at 267.55762 GHz) is presented in Qi et al. 2008 (ApJ, 681, 1396). These SMA data have comparable angular resolution but 203 kHz channel width.

How to Use This casaguide

The data reduction has been split into calibration and imaging pages: (1) TWHydraBand7_Calibration (2) TWHydraBand7_Imaging

You can either start from the beginning using the RawDataAndTablesForReduction directory or begin with imaging from CalibratedData directory.

For tips on different ways CASA can be run, see EVLA_Spectral_Line_Calibration_IRC+10216#How_to_Use_This_casaguide page.

Initial Inspection and Flagging

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