The Radiowave Hunt for Young Stellar Object Emission and Demographics (RADIOHEAD): A Radio Luminosity${-}$Spectral Type Dependence in Taurus${-}$Auriga YSOs (2501.06188v1)

Abstract: We measure the radio continuum fluxes at the locations of all Gaia${-}$confirmed members of Taurus${-}$Auriga using Karl G. Jansky Very Large Array Sky Survey data (VLASS; 2${-}$4 GHz, $\sigma_{\rm{VLASS}}{\sim}110{-}140 \mu$Jy, $2.5''$ resolution) spanning 3 VLASS epochs (2019, 2021, and 2023). We present 35 detections coincident with young Taurus${-}$Auriga stars (29 in individual VLASS images, 6 via stacking). We find a strong dependence on spectral type, wherein the fractional detection rate of radio emission coincident with early-type young stellar objects (YSOs) is systematically higher than late-type YSOs, ranging from 25% $\pm$ 13% for B${-}$F YSOs, 21% $\pm$ 11% for G YSOs, 18.4% $\pm$ 6.3% for K0${-}$K4 YSOs, 15.5% $\pm$ 5.4% for K5${-}$K9 YSOs, 7.0% $\pm$ 2.7% for M0${-}$M2 YSOs, 2.3% $\pm$ 0.9% for M3${-}$M6 YSOs, and 1.9% $\pm$ 1.9% for YSOs with SpTs later than M7. We present cumulative density distributions of radio luminosity densities that demonstrate a significant luminosity enhancement for early- versus late-type YSOs. We find 25% of the detected sources to be significantly variable. We discuss possible interpretations of this dependence, which may reflect stellar magnetic activity, binary interactions, or stellar flaring. We find that mid-infrared YSO class is a strong indicator of radio detectability consistent with higher frequency Taurus-Auriga VLA surveys, with class III stars detected at a rate of 8.8% $\pm$ 1.6%, class IIs at 2.0% $\pm$ 1.2%, and combined class 0s, Is and Fs at 8.0% $\pm$ 5.4%.

• The paper presents a radiowave survey of Young Stellar Objects (YSOs) in Taurus-Auriga using VLASS data, detecting 35 sources and finding a 6% detection fraction.
• Key findings include a strong correlation between radio emission detectability and YSO spectral type (earlier types more detectable) and evolutionary class (Class III more detectable than Class II).
• The study suggests that magnetic activity and binary interactions may contribute to observed radio emissions and variability, highlighting the need for more detailed future radio observations.

Overview of Radio Emissions from Taurus-Auriga YSOs

The paper "The Radiowave Hunt for Young Stellar Object Emission and Demographics (RADIOHEAD)" investigates radio emissions from Young Stellar Objects (YSOs) in the Taurus-Auriga star-forming region using data from the Karl G. Jansky Very Large Array Sky Survey (VLASS). This research focuses on the radio luminosity dependence on spectral types and the evolutionary stages of YSOs, providing insights into the processes driving radio emission in these young stars.

The authors measured radio continuum fluxes at the locations of all Gaia-confirmed members of Taurus-Auriga, detecting 35 sources in VLASS images via either direct observations or stacking techniques. These detections represent a 6% detection fraction across the surveyed region. The research highlights a significant correlation between radio emission detectability and the spectral types of YSOs. Specifically, earlier spectral types (e.g., B, A, F, and G) display higher detection rates compared to later types (e.g., M-type). This spectral type dependence suggests different underlying physical processes influencing radio emissions that are spectral type-dependent.

Variable radio emission was observed in approximately 25% of the detected sources. This variability, coupled with a noted correspondence with binary star systems, implies that interactions within binary systems may enhance radio emission, contributing to the observed variability.

The paper further distinguishes the radio emission detectability between YSO evolutionary classes. Class III YSOs exhibit higher detection fractions than class II, with class 0/I/F sources showing intermediate detectability. This may indicate that class III YSOs, having dispersed their circumstellar material, exhibit less obscured stellar processes, potentially resulting in stronger radio emissions detectable by VLASS.

In Fig. 5 and Fig. 7, the authors underscore the cumulative density distribution of luminosity densities, revealing enhancements for early-type YSOs and differences between evolutionary classes. These cumulative distributions underpin the observed trends in detection fractions and highlight variations in the radiative properties of YSOs linked to their evolutionary stages.

Potential explanations for the observed radio emissions include mechanisms associated with magnetic activity and binary interactions. While limited by the inability to measure emission mechanisms due to VLASS data constraints, the results suggest that stellar multiplicity or magnetic activity could be fundamental in shaping the radio luminosity profile of YSOs.

The implications of this research extend towards understanding the emission mechanisms at play in YSOs and stress the need for further observational investigation. Future work should include more precise radio observations at additional frequencies and polarization studies to untangle the complex processes contributing to radio emissions. Such endeavors will clarify how these emissions evolve with stellar properties and expand knowledge on how YSOs' surrounding environments influence their radiative characteristics.

In summary, this paper provides a comprehensive examination of the dependence of radio emissions on spectral types and evolutionary stages for YSOs in Taurus-Auriga, presenting findings that call for further in-depth explorations using more sensitive and detailed observational tools.