Role of environment and gas temperature in the formation of multiple protostellar systems: molecular tracers

Abstract

Context. Simulations suggest that gas heating due to radiative feedback is a key factor in whether or not multiple protostellar systems will form. Chemistry is a good tracer of the physical structure of a protostellar system, since it depends on the temperature structure. Aims. To study the relationship between envelope gas temperature and protostellar multiplicity. Methods. Single dish observations of various molecules that trace the cold, warm and UV-irradiated gas are used to probe the temperature structure of multiple and single protostellar systems on 7000 AU scales. Results. Single, close binary and wide multiples present similar current envelope gas temperatures, as estimated from H 2 CO and DCO + line ratios. The temperature of the outflow cavity, traced by c−C 3 H 2 , on the other hand, shows a relation with bolometric luminosity and an anti-correlation with envelope mass. Although the envelope gas temperatures are similar for all objects surveyed, wide multiples tend to exhibit a more massive reservoir of cold gas compared to close binary and single protostars. Conclusions. Although the sample of protostellar systems is small, the results suggest that gas temperature may not have a strong impact on fragmentation. We propose that mass, and density, may instead be key factors in fragmentation.

The Formation and Evolution of Wide-orbit Stellar Multiples In Magnetized Clouds

“…Figure 12 divides the binaries, triples, and quadruples into whether they are composed of all Stage 0, all Stage 1, or a mixture at the end of each multiple. Observations support a picture that turbulent fragmentation typically does not create co-eval protostars (Murillo et al 2018). Co-evality (or lack thereof) between protostars in bound pairs may be a clue to their formation origins, which we discuss in Section 4.…”

“…Protostellar outflows drive turbulence on small scales and reduce the accretion rates onto stars and the overall star formation effeciency (Offner & Arce 2014;Offner & Chaban 2017;Cunningham et al 2018). A diffuse radiative component can discourage fragmentation on the disk-size scale, but numerical and observational evidence suggest this component does not suppress fragmentation on the scales considered here (Offner et al 2010;Murillo et al 2018). The coupling between the gas and the magnetic field through the ideal MHD approximation allows angular momentum transport to occur more efficiently than a simulation that employed non-ideal effects.…”

A cold accretion flow onto one component of a multiple protostellar system

“…With the same luminosity assumption, source B (L bol = 3 L ) would have an accretion rate of a few 10 −7 M yr −1 . Preferential accretion of material could be key in multiple protostellar system formation and evolution (Murillo et al 2018a). In particular, uneven delivery of material in wide multiple protostars (separations larger than disk radius) could provide insight into systems with components at different evolutionary stages (Murillo et al 2016).…”

“…However, processes within cloud cores, such as episodic accretion (e.g., Hsieh et al 2018), warm inner envelopes (Jørgensen et al 2005;Tobin et al 2010;Belloche et al 2020), or gas temperatures below N 2 freeze-out (e.g., VLA1623: Bergman et al 2011;Murillo et al 2018b) can change the distribution of molecular gas along structures in the cloud core. Cloud cores of both single and multiple protostellar systems present HCN emission in single dish observations (e.g., Murillo et al 2018a), suggesting it can also be a good tracer of cloud core structure (Tafalla et al 2002(Tafalla et al , 2004. Being able to trace how material is transported from molecular cloud to protostellar cloud core scales can shed light onto the mass accretion process in star formation.…”

Formación de estrellas múltiples de masa baja

“…La formación y destrucción de ciertas moléculas depende de la densidad y temperatura del gas en donde se ubican, por ende, su distribución da indicios de las condiciones físicas y químicas (Hsieh et al 2018;Murillo et al 2018b). Cuantitativamente, la temperatura y densidad se pueden derivar a través de las fracciones de la intensidad de I Congreso Internacional de Ciencias Exactas y Naturales Universidad Nacional Costa Rica, 2019 3 emisión molecular (Murillo et al 2018c). Para ello se requieren dos o más transiciones rotacionales de una especie molecular.…”