Zooming in on protostellar outflows: A Combined JWST and ALMA Study of the very low mass, Class 0 protostar IRAS 16253-2429

Mayank Narang^1*, Nagayoshi Ohashi¹

¹Astronomy, ASIAA, Taipei, Taiwan

* Presenter:Mayank Narang, email:mayankn1154@gmail.com

We present a joint ALMA & JWST study of the IRAS 16253 protostar, combining
data from the eDisk & Investigating Protostellar Accretion Programs. This very low-mass protostar in rho-Oph has a mass of 0.12 Msun & a luminosity of 0.2 Lsun. With ALMA & JWST, we trace the flows of gas during the protostellar phase that drives the formation process of stars & planetary systems. During their primary
accretion phase, protostars are too deeply embedded to be studied in the optical & NIR wavelengths. With JWST, we can detect these deeply embedded Class 0 protostars. Using NIRSpec & MIRI IFUs, we spectral image the 2.9-29 micron
wavelength range with a resolution of 30 au at the distance of rho-Oph. While JWST
can map the ionic & molecular species, including H2, in shock-heated gas, it doesn’t have sufficient velocity resolution to study the gas kinematics. Using ALMA, we can detect the cool in lines of isotopologues of CO that trace the cold gas that dominates the mass of envelopes & outflows with similar spatial resolution. Our analyses reveal
a highly collimated, ~500 au long (dynamical time scale 34 yrs) jet in [Fe II], while no such collimated molecular jet is detected with ALMA. We find that the radius of this jet is about 40-50 au, comparable to the radius of the protostellar disk (50 au). The
CO outflow also has a similar radius. This hints that jet & outflow originate from the
entire disk surface. The absence of the molecular jet raises intriguing questions
about the underlying mechanisms of launching jets & outflows from protostars. In the cavities, we find jets traced in ions but without molecules. Using JWST, we measure the velocity (~150 km/s) & the mass flow through the jet, indicating a low mass flow of ~10^-10 Msun/yr. We map both shocks from H2 & entrained gas from ALMA CO lines. Together, these data show how ALMA & JWST can link the jets & winds driving the outflows to the flows of entrained gas responsible for lowering the star formation efficiency.

Keywords: Protostars, Jets, Star formation