High-mass Star Formation and Observational Tips Patricio Sanhueza High-Mass stars vs Low-Mass stars High-Mass Low-Mass Mass larger than 8 M⨀ Mass less than 8 M⨀ Large amount of ionizing radiation Low amount of ionizing radiation Evolve quickly, die soon Evolve slowly, last much much longer End their life as Supernova End their life as a Planetary Nebula Form elements heavier than Iron Form light elements Why are high-mass stars important? – Massive stars (> 8 M⨀) play a key role in the evolution of the energetics and chemistry of molecular clouds and galaxies • Stellar winds • UV radiation • Supernovae • Most stars form in clusters with high-mass stars Hubble Heritage Project M 83 And yet their formation remains an open problem 3 What are the challenges, why high-mass star formation has been hard to study • High-mass stars are rare and evolve quickly • They are born in highly clustered regions • High-mass star-forming regions are mostly located at large distances • High-mass star-forming regions are deeply embedded in Image from ESO. molecular clouds M 17 4 4 Infrared Dark Clouds (IRDCs) Spitzer: 8 µm •Infrared Dark Clouds (IRDCs) are molecular clouds observed as dark silhouettes against the mid-IR background and are known to form high- mass stars 5 Where do they form? M 17 Orion Optical, IR, Radio Observations Optical, IR, Radio Observations Optical, IR, Radio Observations G28.23: Infrared dark clouds IR G28.23: Infrared dark clouds IR G28.23: Infrared dark clouds Radio (ALMA) IR Infrared Dark Cloud Prestellar Protostellar Hot Core H II Region Phase Phase Phase Phase Core Clump - Initial collapse - Young accretion - Accretion disk - High-Mass star - Cold gas disk - Powerful outflows - UV radiation - Freezing of - Young outflow - Strong winds - Strong winds molecules - Warm gas - Complex molecules - No embedded - CO is release to IR sources the gas phase TimeTemperature 9 Main observing tool: Radio interferometers ALMA Infrared Dark Cloud Prestellar Protostellar Hot Core H II Region Phase Phase Phase Phase Core Clump - Initial collapse - Young accretion - Accretion disk - High-Mass star - Cold gas disk - Powerful outflows - UV radiation - Freezing of - Young outflow - Strong winds - Strong winds molecules - Warm gas - Complex molecules - No embedded - CO is release to IR sources the gas phase TimeTemperature 12 Infrared Dark Cloud Prestellar Protostellar Hot Core H II Region Phase Phase Phase Phase Core Clump - Initial collapse - Young accretion - Accretion disk - High-Mass star - Cold gas disk - Powerful outflows - UV radiation - Freezing of - Young outflow - Strong winds - Strong winds molecules - Warm gas - Complex molecules - No embedded - CO is release to IR sources the gas phase TimeTemperature 13 Tip 1: mapping large objects, using mosaics 54±2904000 ° G327.116-00.294 3.6, 4.5, 8.0 µm IRDC G327.116-00.294 24 µm 70 µm 3000000 2000 4000 Dec (J2000) 3100000 0.3 pc 1.5’ = 1.3 pc 2000 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s Tip 1: mapping large objects, 54±3000000 using° mosaicsG327.116-00.294 54±2904000 1200 ° G327.116-00.294 3.6, 4.5, 8.0 µm IRDC G327.116-00.294 24 µm 70 µm 3000000 2400 2000 4000 36 Dec (J2000) 00 Dec (J2000) 3100000 4800 0.3 pc 1.5’ = 1.3 pc 2000 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s 3100000 0.3 pc 51m00s 58s 15h50m56s RA (J2000) Tip 1: mapping large objects, using mosaics 54±2904000 ° G327.116-00.294 3.6, 4.5, 8.0 µm IRDC G327.116-00.294 24 µm 54±3000000 70 µm ° G327.116-00.294 3000000 1200 2400 2000 36 Dec (J2000) 00 4000 Dec (J2000) 4800 3100000 3100000 0.3 pc 51m00s 58s 15h50m56s 0.3 pc 1.5’ = 1.3 pc RA (J2000) 2000 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s Tip 1: mapping large objects, using mosaics 54±2904000 ° G327.116-00.294 3.6, 4.5, 8.0 µm IRDC G327.116-00.294 24 µm 54±3000000 70 µm ° G327.116-00.294 3000000 1200 2400 2000 36 Dec (J2000) 00 4000 Dec (J2000) 4800 3100000 3100000 0.3 pc 51m00s 58s 15h50m56s 0.3 pc 1.5’ = 1.3 pc RA (J2000) 2000 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s Tip 1: mapping large objects, using mosaics 54±2904000 ° G327.116-00.294 3.6, 4.5, 8.0 µm IRDC G327.116-00.294 24 µm 54±3000000 70 µm ° G327.116-00.294 3000000 1200 2400 2000 36 Dec (J2000) 3600 Dec (J2000) 00 4000 Dec (J2000) 4800 3100000 3100000 0.3 pc 51m00s 58s 15h50m56s 0.3 pc 1.5’ = 1.3 pc RA (J2000) 2000 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s Tip 2: mapping large objects, adding 7 m array Field of view is proportional to 54±2904000 ° G327.116-00.294 3.6, 4.5, 8.0 µm IRDC G327.116-00.294 24 µm FOV ~ �/D 70 µm 30 00 0 00 For 12 m array at 224 GHz (1.34 mm), the FOV is ~23” 2000 For the 7 m array at the same 4000 frequency is 40” Dec (J2000) 3100000 0.3 pc 1.5’ = 1.3 pc 2000 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s 03s 51m00s 57s 15h50m54s Tip 2: mapping large objects, adding 7 m array 12 m 12 m + 7 m 19±2700000 ° G010.991-00.082 3.6, 4.5, 8.0 µm 24 µm 70 µm 2000 4000 2800000 Dec (J2000) 2000 0.3 pc 4000 10s 08s 06s 18h10m04s 10s 08s 06s 18h10m04s 10s 08s 06s 18h10m04s In my survey, after adding the 7 m array 20% more cores are detected and the flux per core increase on average a factor 1.6 (~50%) Tip 2: mapping large objects, adding 7 m array G010.991-00.082 12 m 12 m + 7 m 19±2702400 ° 19±2700000 ° G010.991-00.082 3.6, 4.5, 8.0 µm 24 µm 70 µm 3600 2000 4000 4800 2800000 Dec (J2000) Dec (J2000) 2800000 2000 0.3 pc 1200 4000 10s 08s 06s 18h10m04s 10s 08s 06s 18h10m04s 10s 08s 06s 18h10m04s 0.3 pc 2400 09s 08s 07s 06s 18h10m05s RA (J2000) In my survey, after adding the 7 m array 20% more cores are detected and the flux per core increase on average a factor 1.6 (~50%) Tip 2: mapping large objects, adding 7 m array G010.991-00.082 12 m G010.991-00.082 12 m + 7 m 19±2702400 19±2702400 ° ° 19±2700000 ° G010.991-00.082 3.6, 4.5, 8.0 µm 24 µm 70 µm 3600 3600 2000 4000 4800 4800 2800000 Dec (J2000) Dec (J2000) Dec (J2000) 2800000 2800000 2000 0.3 pc 1200 1200 4000 10s 08s 06s 18h10m04s 10s 08s 06s 18h10m04s 10s 08s 06s 18h10m04s 0.3 pc 0.3 pc 2400 2400 09s 08s 07s 06s 18h10m05s 09s 08s 07s 06s 18h10m05s RA (J2000) RA (J2000) In my survey, after adding the 7 m array 20% more cores are detected and the flux per core increase on average a factor 1.6 (~50%) Tip 3: mapping large objects, adding TP C18O J=2-1 Tip 3: mapping large objects, adding TP C18O J=2-1 12 m array Tip 3: mapping large objects, adding TP C18O J=2-1 12 m array 12 m + 7 m array Tip 3: mapping large objects, adding TP C18O J=2-1 12 m array 12 m + 7 m array 12 m + 7 m + TP array Infrared Dark Cloud Prestellar Protostellar Hot Core H II Region Phase Phase Phase Phase Core Clump - Initial collapse - Young accretion - Accretion disk - High-Mass star - Cold gas disk - Powerful outflows - UV radiation - Freezing of - Young outflow - Strong winds - Strong winds molecules - Warm gas - Complex molecules - No embedded - CO is release to IR sources the gas phase TimeTemperature 20 Infrared Dark Cloud Prestellar Protostellar Hot Core H II Region Phase Phase Phase Phase Core Clump - Initial collapse - Young accretion - Accretion disk - High-Mass star - Cold gas disk - Powerful outflows - UV radiation - Freezing of - Young outflow - Strong winds - Strong winds molecules - Warm gas - Complex molecules - No embedded - CO is release to IR sources the gas phase TimeTemperature 20 Tip 4: observing bright compact objects, self-calibration Dynamic range limited image, S/N ratio = 450 S = peak source emission, N = noise 0.1 pc https://casaguides.nrao.edu/index.php/First_Look_at_Self_Calibration https://casaguides.nrao.edu/index.php?title=VLA_Self-calibration_Tutorial-CASA5.7.0 Tip 4: observing bright compact objects, self-calibration Dynamic range limited image, S/N ratio = 450 S/N ratio = 920 S = peak source emission, N = noise 0.1 pc https://casaguides.nrao.edu/index.php/First_Look_at_Self_Calibration https://casaguides.nrao.edu/index.php?title=VLA_Self-calibration_Tutorial-CASA5.7.0 Tip 5: observing bright compact objects, line contamination Hot core 22 Tip 5: observing bright compact objects, line contamination FDM mode SPW 1 Hot core SPW 2 SPW 3 SPW 4 22 Thanks.