Title Proving the existence of Keplerian rotation about a 20 solar masses young star Pi M. Beltran Time 55 hrs DRSP 2.0 - section 2.2 proposal 1. Name: Proving the existence of Keplerian rotation about a 20 solar masses young star Authors: M.Beltran 2. Science goal: G24.78+0.08 A1 is a unique example of a bipolar outflow/rotating toroid system undergoing infall towards a central O star with a mass of ~20 solar masses, based on the free-free continuum flux at cm wavelengths. Unlike disks in lower mass stars, the rotation curve of this toroid, which has a mass of ~130 solar masses and a diameter of ~0.04 pc, is not Keplerian. "True" circumstellar disks, which have been found in B type stars (e.g. Cesaroni et al. 2006), might be so elusive in O stars due to an observational bias, since O stars are on average more distant than B stars. However, disks might be "hidden" inside the massive toroids. Therefore, despite the large mass of the toroid, close enough to the star rotation might become Keplerian: this will occur inside the radius enclosing a gas mass comparable to that of the star, which for G24.78+0.08 A1 is ~0.5". The goal of this proposal is (i) to prove the existence of a Keplerian accretion disk around a young O star; and (ii) to obtain a precise estimate of the stellar mass to be compared with that derived from the free-free continuum of the associated hypercompact HII region. This goal can be achieved by imaging 13-CH3CN transitions in the densest parts of the rotating toroid. The advantage of observing the optically thin isotopomer 13-CH3CN instead of CH3C-13N, which are expected to have the same intensity (Olmi et al. 1996), is that CH3C-13N lines are affected by blending with the K >= 5 components of CH3CN. On the other hand, CH3CN lines could be too optically thick to trace the region of 1" in diameter. By observing different transitions of 13-CH3CN, it will be possible to measure the rotational temperature (which one expects to be ~equal to the kinetic temperature) and column density of the gas in the embedded disk by means of the rotation diagram method. For this purpouse it may be useful to observe different transitions of CH3C-13N (and/or CH3CN v8=1, vibrationally excited) as well. 3. Number of sources: 1 4. Coordinates: 4.1. Rough RA and DEC RA = 18:36:12.57, DEC= -07:12:10.9 4.2. Moving target: no 4.3. Time critical: no 4.4. Scheduling constraints: (optional) 5. Spatial scales: 5.1. Angular resolution: ~< 0.5 arcsec 5.2. Range of spatial scales: up to 3 arcsec 5.3. Required pointing accuracy: 1'' ##### Maite: is this pointing accuracy reasonable? Also, I added section below saying you don't need ACA. 6. Observational setup 6.1. Single dish total power data: no Observing modes for single dish total power: (e.g., nutator switch; frequency switch; position switch; on-the-fly mapping; and combinations of the above) 6.2. Stand-alone ACA: no 6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: no 6.4. Subarrays of 12m baseline-ALMA antennas: no 7. Frequencies: 7.1. Receiver Bands: 4 & 6 & 8 ------------------------------------------------------------------ 7.2 Lines and Frequencies (GHz): Band 4 Lines & Frequencies: (13)CH3CN 7(0)-6(0) 125.061 GHz \ CH3(13)CN 7(0)-6(0) 128.716 GHz | 4.1 GHz sep CH3CN 7(0)-6(0) v8=1 l=+1 129.162 GHz / (13)CH3CN 8(0)-7(0) 142.926 GHz \ CH3(13)CN 8(0)-7(0) 147.102 GHz | 4.7 GHz sep CH3CN 8(0)-7(0) v8=1 l=+1 147.611 GHz / ##### Band 4: Max separation allowed within one sideband = 4 GHz. USB and LSB are separated by 8 GHz so you can observe lines that are separated by 8-16 GHz or within 4 GHz. You have to observe the 125 GHz line separate from 128/129 GHz and observe the 142 GHz line separate from the 147 GHz lines. 22.6 GHz separation between 125 and 147 GHz lines. ==> need to observe each group separately (can't get them in USB and LSB). Band 6 Lines & Frequencies: (13)CH3CN 12(0)-11(0) 214.374 GHz \ CH3(13)CN 12(0)-11(0) 220.638 GHz | 7 GHz sep CH3CN 12(0)-11(0) v8=1 l=+1 221.394 GHz / ##### Band 6: Max separation allowed within one sideband = 4 GHz. USB and LSB are separated by 12 GHz although you can get a separation of only 8 GHz with some decrease in performance. You can observe the 220 and 221 GHz lines together but will have to get the 214 GHz line separately. Band 8 Lines & Frequencies: (13)CH3CN 26(0)-25(0) 464.277 GHz \ CH3(13)CN 26(0)-25(0) 477.838 GHz | 15 GHz sep CH3CN 26(0)-25(0) v8=1 l=+1 479.369 GHz / ##### Band 8: Max separation allowed within one sideband = 4 GHz. USB and LSB are separated by 8 GHz so you can observe lines that are separated by 8-16 GHz or within 4 GHz. So you can get these in one observation, 477/479 lines in the USB and 464 line in the LSB. ------------------------------------------------------------------- 7.3. Spectral resolution (km/s): ~<0.3 km/s 7.4. Bandwidth or Spectral coverage (km/s or GHz): <20 km/s ##### Maite: I would recommend making the BW larger here so you can subtract continuum easily if you need it. Say, 50-100 km/s? This is easy for ALMA. 8. Continuum flux density: 8.1. Typical value: total flux ~0.2-1 Jy spread over ~1.5" at (2mm and 1mm). Continuum peak value expected to be a few mJy/beam for a <0.5" resolution 8.2. Required continuum rms: 0.1 mJy/b 8.3. Dynamic range in image: low 8.4. Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) 5% repeatability ( 1-3% / 5% / 10% / n/a ) 5% relative ( 1-3% / 5% / 10% / n/a ) 5% ##### Maite: Is this reasonable calibration accuracy for your project? 1-3% is hard to do so only ask for it if you need it. But if you need it to get the rotation diagram accurate, then specify 1-3%. 9. Line intensity: 9.1. Typical value: expected ~0.5-1 K for band 4 transitions and 3-4 K for band 6, for a resolution of 0.5" unknown for band 8 transitions 9.2. Required rms per channel: 0.1-0.2 K, depending on the band 9.3. Spectral dynamic range: low 9.4. Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) 5% repeatability ( 1-3% / 5% / 10% / n/a ) 5% relative ( 1-3% / 5% / 10% / n/a ) 5% ##### Maite: again, check to make sure this is reasonable. 10. Polarization: no 10.1. Required Stokes parameters: 10.2. Total polarized flux density (Jy): 10.3. Required polarization rms and/or dynamic range: 10.4. Polarization fidelity: 10.5. Required calibration accuracy: 11. Integration time for each observing mode/receiver setting (hr): Band 3: rms ~0.1 K (line brightness) per 10 hours integration time, for a spectral resoluion of 1 km/s and resolution of 0.5" per tuning. ##### Maite: multiply this by 4 based on arguments above. Band 6: rms 0.2 K (line brightness) per 20 hours integration time, for a spectral resolution of 0.3 km/s and resolution of 0.3" Probably, the band 6 is the most suitable to carry on the kinematical study of the velocity field, that's why better spectral and angular resolutions are required. ##### Maite: multiply this by 2. Band 7: rms 0.2 K (line brightness) per 15 hours integration time, for a spectral resolution of 0.3 km/s and resolution of 0.3". The transitions in this band would probably allow us to trace material closer to the central star, however, the expected line intensities for the transitions in this band are unknown. 12. Total integration time for program: 55 hr on source with ALMA + overheads (pointing etc). ##### Maite: So total observing time would be 4x10 + 2x20 + 15 = 95 hours plus overhead. 13. Comments on observing strategy : (optional) (e.g. line surveys, Target of Opportunity, Sun, ...): DRSP 2.0 - section 2.2 proposal 1. Name: Proving the existence of Keplerian rotation about a 20 solar masses young star Authors: M.Beltran 2. Science goal: G24.78+0.08 A1 is a unique example of a bipolar outflow/rotating toroid system undergoing infall towards a central O star with a mass of ~20 solar masses, based on the free-free continuum flux at cm wavelengths. Unlike disks in lower mass stars, the rotation curve of this toroid, which has a mass of ~130 solar masses and a diameter of ~0.04 pc, is not Keplerian. "True" circumstellar disks, which have been found in B type stars (e.g. Cesaroni et al. 2006), might be so elusive in O stars due to an observational bias, since O stars are on average more distant than B stars. However, disks might be "hidden" inside the massive toroids. Therefore, despite the large mass of the toroid, close enough to the star rotation might become Keplerian: this will occur inside the radius enclosing a gas mass comparable to that of the star, which for G24.78+0.08 A1 is ~0.5". The goal of this proposal is (i) to prove the existence of a Keplerian accretion disk around a young O star; and (ii) to obtain a precise estimate of the stellar mass to be compared with that derived from the free-free continuum of the associated hypercompact HII region. This goal can be achieved by imaging 13-CH3CN transitions in the densest parts of the rotating toroid. The advantage of observing the optically thin isotopomer 13-CH3CN instead of CH3C-13N, which are expected to have the same intensity (Olmi et al. 1996), is that CH3C-13N lines are affected by blending with the K >= 5 components of CH3CN. On the other hand, CH3CN lines could be too optically thick to trace the region of 1" in diameter. By observing different transitions of 13-CH3CN, it will be possible to measure the rotational temperature (which one expects to be ~equal to the kinetic temperature) and column density of the gas in the embedded disk by means of the rotation diagram method. For this purpose it may be useful to observe different transitions of CH3C-13N (and/or CH3CN v8=1, vibrationally excited) as well, if it's possible to observe them simultaneously with the 13-CH3CN lines. 3. Number of sources: 1 4. Coordinates: 4.1. Rough RA and DEC RA = 18:36:12.57, DEC= -07:12:10.9 4.2. Moving target: no 4.3. Time critical: no 4.4. Scheduling constraints: (optional) 5. Spatial scales: 5.1. Angular resolution: ~< 0.5 arcsec 5.2. Range of spatial scales: up to 3 arcsec 5.3. Required pointing accuracy: 1'' 6. Observational setup 6.1. Single dish total power data: no Observing modes for single dish total power: (e.g., nutator switch; frequency switch; position switch; on-the-fly mapping; and combinations of the above) 6.2. Stand-alone ACA: no 6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: no 6.4. Subarrays of 12m baseline-ALMA antennas: no 7. Frequencies: 7.1. Receiver Bands: 4 & 6 & 8 ------------------------------------------------------------------ 7.2 Lines and Frequencies (GHz): #### In the list below, it appears only the frequency for the K=0 component, but the goal of the proposal is to observe as many K components as possible. Band 4 Lines & Frequencies: (13)CH3CN 7(0)-6(0) 125.061 GHz CH3(13)CN 7(0)-6(0) 128.716 GHz (13)CH3CN 8(0)-7(0) 142.926 GHz ##### Band 4: (13)CH3CN 7-6 can be observed simultaneously with CH3(13)CN 7-6 as they fall within one sideband of 4 GHz. (13)CH3CN 8-7 will be observed separately with a different tuning. Band 6 Lines & Frequencies: (13)CH3CN 12(0)-11(0) 214.374 GHz Band 8 Lines & Frequencies: (13)CH3CN 26(0)-25(0) 464.277 GHz CH3(13)CN 26(0)-25(0) 477.838 GHz CH3CN 26(0)-25(0) v8=1 l=+1 479.369 GHz ##### Band 8: these lines can be observed simultaneously by placing (13)CH3CN 26-25 in the LSB and CH3(13)CN 26-25 and CH3CN 26-25 v8=1 l=+1 in the USB. ------------------------------------------------------------------- 7.3. Spectral resolution (km/s): ~<0.3 km/s 7.4. Bandwidth or Spectral coverage (km/s or GHz): 50-100 km/s 8. Continuum flux density: 8.1. Typical value: total flux ~0.2-1 Jy spread over ~1.5" at (2mm and 1mm). Continuum peak value expected to be a few mJy/beam for a <0.5" resolution 8.2. Required continuum rms: 0.1 mJy/b 8.3. Dynamic range in image: low 8.4. Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) 5% repeatability ( 1-3% / 5% / 10% / n/a ) 5% relative ( 1-3% / 5% / 10% / n/a ) 5% 9. Line intensity: 9.1. Typical value: expected ~0.5-1 K for band 4 transitions and 3-4 K for band 6, for a resolution of 0.5" unknown for band 8 transitions 9.2. Required rms per channel: 0.1-0.2 K, depending on the band 9.3. Spectral dynamic range: low 9.4. Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) 5% repeatability ( 1-3% / 5% / 10% / n/a ) 5% relative ( 1-3% / 5% / 10% / n/a ) 5% 10. Polarization: no 10.1. Required Stokes parameters: 10.2. Total polarized flux density (Jy): 10.3. Required polarization rms and/or dynamic range: 10.4. Polarization fidelity: 10.5. Required calibration accuracy: 11. Integration time for each observing mode/receiver setting (hr): Band 4: rms ~0.1 K (line brightness) per 10 hours integration time, for a spectral resolution of 1 km/s and resolution of 0.5" per tuning. Therefore, a total of 20 hours integration time for the 2 tunings. Band 6: rms 0.2 K (line brightness) per 20 hours integration time, for a spectral resolution of 0.3 km/s and resolution of 0.3" Probably, bands 6 and 8 are the most suitable to carry on the kinematical study of the velocity field, that's why better spectral and angular resolutions are required. Band 7: rms 0.2 K (line brightness) per 15 hours integration time, for a spectral resolution of 0.3 km/s and resolution of 0.3". The transitions in this band would probably allow us to trace material closer to the central star, however, the expected line intensities for the transitions in this band are unknown. 12. Total integration time for program: 2x10 + 20 + 15 = 55 hr on source with ALMA plus overhead 13. Comments on observing strategy : (optional) (e.g. line surveys, Target of Opportunity, Sun, ...): -------------------------------------------------- Review v2.0: 2.2.12 - 2.2.15 I found no problems with these proposals other than the standard question of calculating ACA time.