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Sub-millimeter wavelength protostellar accretion rate monitoring with AtLAST

Thomas Stanke, Verena Wolf, Bringfried Stecklum, Doug Johnstone, Jochen Eislöffel, Gregory J. Herczeg, S. Tom Megeath, Karri I. I. Koljonen

TL;DR

The paper addresses how to characterize protostellar accretion variability during the earliest, heavily obscured stages. It argues for decade-scale, wide-field sub-millimeter monitoring with a large ground-based single-dish telescope to overcome envelope opacity and to statistically constrain bursts across mass ranges. It proposes the AtLAST concept—a 50 m dish with up to 2° instantaneous FoV, operating to 950 GHz with ~1.5'' resolution, achieving a mapping speed up to $10^5$ times faster than ALMA and high continuum sensitivity. This approach would link observed sub-millimeter variability to instantaneous accretion rates, addressing the protostellar luminosity problem and enabling sub-millimeter transient science as a major tool for understanding early star formation.

Abstract

How a star forms is a fundamental question in astrophysics. In the earliest stages of protostellar evolution high extinction prevents a direct study of the accretion processes and their temporal evolution. Monitoring the variations of the accretion luminosity in a large protostar sample over decades is needed to reveal how protostars accrete -- in major bursts or in a quasi-steady fashion. We here argue that a large ground based sub-millimeter single-dish facility with a wide FoV is required to fulfill this task.

Sub-millimeter wavelength protostellar accretion rate monitoring with AtLAST

TL;DR

The paper addresses how to characterize protostellar accretion variability during the earliest, heavily obscured stages. It argues for decade-scale, wide-field sub-millimeter monitoring with a large ground-based single-dish telescope to overcome envelope opacity and to statistically constrain bursts across mass ranges. It proposes the AtLAST concept—a 50 m dish with up to 2° instantaneous FoV, operating to 950 GHz with ~1.5'' resolution, achieving a mapping speed up to times faster than ALMA and high continuum sensitivity. This approach would link observed sub-millimeter variability to instantaneous accretion rates, addressing the protostellar luminosity problem and enabling sub-millimeter transient science as a major tool for understanding early star formation.

Abstract

How a star forms is a fundamental question in astrophysics. In the earliest stages of protostellar evolution high extinction prevents a direct study of the accretion processes and their temporal evolution. Monitoring the variations of the accretion luminosity in a large protostar sample over decades is needed to reveal how protostars accrete -- in major bursts or in a quasi-steady fashion. We here argue that a large ground based sub-millimeter single-dish facility with a wide FoV is required to fulfill this task.

Paper Structure

This paper contains 3 sections, 2 figures.

Table of Contents

  1. Scientific context and motivation
  2. Science case
  3. Technical requirements

Figures (2)

  • Figure 1: The first detected accretion burst in a Class 0 protostar (HOPS 383) as seen at sub-millimeter wavelengths (taken from Safron et al. 2015 Safron2015). The outburst started some time between October 2004 and October 2006. Left: JCMT/SCUBA 450 $\mu$m image taken in 1998, middle: APEX/SABOCA 350 $\mu$m image taken in 2011, right: ratio of post- to pre-burst image. Only a substantial rise in sub-millimeter flux due to the accretion outburst (detected at mid-IR wavelengths) can explain the ratio of the post-burst 350 $\mu$m to pre-burst 450 $\mu$m flux seen for HOPS 383. Later monitoring (2016-2020, Lee2021) showed the sub-millimeter flux decreasing by a few percent per year.
  • Figure 1: Fischer ea. 2024 Fischer2024 Fig. 3: ratio of observed flux variation to actual burst amplitude at various wavelengths. The horizontal lines in the violin plots mark the first quartile (bottom), median (central), and third quartile (top) of each distribution. Space-based (PRIMA) far-IR observations trace the bursts most directly with small scatter, followed by sub-millimeter observations. The mid-IR range is sensitive to bursts, but shows a large scatter of observed vs. actual burst amplitude due to a strong dependency on source and viewing geometry.