Combination of ALMAGAL with APEX single-pointing observations to solve the missing flux problem

Han-Tsung Lee^1*, Peter Schilke¹, Gary Fuller^1,2, Alvaro Sanchez-Monge³, Beth Jones¹

¹I. Physikalisches Institut, University of Cologne, Cologne, Germany
²Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Manchester, UK
³Institute of Space Sciences, Barcelona, Spain

* Presenter:Han-Tsung Lee, email:hantsunglee@gmail.com

High-mass stars play key roles in affecting star formation process. ALMAGAL, an ALMA large program observing >1000 high-mass star-forming regions in the Galaxy provides unprecedented opportunities to study broad aspects of the birth and evolution of massive (proto)stars. However, severe missing flux is found toward the ALMAGAL data due to the lack of total power observations. Here, we explore an alternative method to solve the missing flux problem in ALMAGAL line observations that combine ALMAGAL with APEX single-pointing data as short-spacing complements. We show that generally good recoveries of flux can be achieved by comparing our results with the images combined with OTF maps from APEX for several benchmarking sources. We investigate the impact of missing flux on the derivation of physical parameters using dense gas tracer H₂CO, finding that gas temperatures can be underestimated by 25-100 K with the interferometric-only data, and fake infall signatures can be caused by the missing flux, leading to misidentification of infall motions toward massive star-forming regions.

Keywords: Interferometers, Star formation, Massive stars, Interstellar line emission