Title The photospheres and proper motions of normal stars Pi Black Time 200 hrs 1. Name: The photospheres and proper motions of normal stars Authors: Black, Aalto et al 2. Science goal: Photospheric studies: Although the investigation of normal stars is usually considered the realm of UV, visible, and infrared astronomy, ALMA will afford sufficient sensitivity to observe photospheres of normal stars in the Galaxy. At first glance, one would think that stars in the Magellanic Clouds would lie beyond the reach even of ALMA. However, we know from IR surveys of red supergiants and AGB stars that the LMC and SMC contain several such stars with 10-$\mu$m magnitudes of the order of 5 or brighter. With a Rayleigh-Jeans extrapolation from 10 $\mu$m to mm/submm wavelengths, [10] = 5 mag corresponds to flux densities of 0.028 mJy at 250 GHz, 0.054 mJy at 345 GHz, and 0.22 mJy at 700 GHz. According to the ALMA sensitivity calculator, these continuum flux levels correspond to 2$\sigma$, 2$\sigma$, and 1 $\sigma$ at 250, 345 and 700 GHz, respectively, in 3600 seconds of integration. We can also estimate the observability of Galactic stars with known 250 GHz fluxes if moved to the 50 kpc distance of LMC. examples: star f250(mJy) D(kpc) f(250@D=50 kpc) S/N(after 1 hr) --------------------------------------------------------------- P Cyg 146 1.8 0.19 13sigma WR 147 379 0.63 0.060 4 VY CMa 338 1.1 0.16 11 VV Cep 45 0.86 0.013 0.9 --------------------------------------------------------------- Proper motions: Quasars behind the MC also provide astrometric reference for measurements of proper motion (see prop. on background QSOs). ALMA will have sufficient sensitivity at mm and submm wavelengths for direct measurements of stars in the MC. It may also be possible to achieve better astrometric precision on both MC stars and background quasars than is possible with optical techniques. Needless to say, measurement of proper motions in the MC will be an important step in a more accurate calibration of the first step in the cosmological distance ladder (Anguita, Loyola, \&\ Pedreros et al. 2000 and references therein). Measurements of such proper motions are also important for studying the internal dynamics of the LMC and SMC and the dynamics of the Magellanic Stream and Local Group. Systemic proper motions for the MC are expected to be of the order of a few milliarcsecond per year. With a beam of 16 mas we expect the positional accuracy to be at least 5 times better than that - enough to detect proper motion in a year or two. 3. Number of sources: 100 4. Coordinates: 4.1. 60 sources in 30 Doradus and N159, LMC (RA=05h40m, DEC=-69d) 40 sources in the SMC (RA=01h, DEC=-73d) 4.2. Moving target: no 4.3. Time critical: no 5. Spatial scales: 5.1. Angular resolution: 0.0018" (in 2003: 0.016" but cannot be reached now) 5.2. Range of spatial scales/FOV: At 250 GHz (Band 6) the field-of-view is about 35" 5.3. Single dish: no 5.4. ACA: no 5.5. Subarrays: no 6. Frequencies: 250 GHz 6.1. Receiver band: Band 6 6.2. Lines: - Frequency: 6.3. Spectral resolution (km/s): - 6.4. Spectral coverage (km/s or GHz): - 7. Continuum flux density: 7.1. Typical value: 0.014-1 mJy 7.2. Continuum peak value: 7.3. Required continuum rms: 0.014 mJy 7.4. Dynamic range in image: 8. Line intensity: 8.1. Typical value:- 8.2. Required rms per channel: - 8.3. Spectral dynamic range: - 9. Polarization: no 10. Integration time per setting: 2 hrs (In 2003: 1 hr) 11. Total integration time for program: 100x2 hr=200 hrs repeat at end of three year period - add on another 200 hrs. ********************************************************** -------------------------------------------------- Review v2.0: 1. Name: The photospheres and proper motions of normal stars Authors: Black, Aalto et al DRSP2.0 Review Leonardo Testi: Why 250GHz? Most probably is the best tradeoff between sensitivity and angular resolution? Time estimate is uncertain, but we can have this program as baseline with 200hrs for the time being.