L1448 IRS2E: A candidate first hydrostatic core

TL;DR

This paper presents high-resolution observations of L1448 IRS2E, a candidate first hydrostatic core, showing it drives a molecular outflow at an extremely low luminosity, consistent with theoretical models of early star formation.

Contribution

It provides the first observational evidence of a candidate first hydrostatic core driving an outflow at very low luminosity, supporting theoretical predictions.

Findings

L1448 IRS2E has an extremely low luminosity (< 0.1 L_sun).

It drives a molecular outflow despite being infrared dark.

The source is at an evolutionary stage between prestellar cores and Class 0 protostars.

Abstract

Intermediate between the prestellar and Class 0 protostellar phases, the first core is a quasi-equilibrium hydrostatic object with a short lifetime and an extremely low luminosity. Recent MHD simulations suggest that the first core can even drive a molecular outflow before the formation of the second core (i.e., protostar). Using the Submillimeter Array and the Spitzer Space Telescope, we present high angular resolution observations towards the embedded dense core IRS2E in L1448. We find that source L1448 IRS2E is not visible in the sensitive Spitzer infrared images (at wavelengths from 3.6 to 70 um), and has weak (sub-)millimeter dust continuum emission. Consequently, this source has an extremely low bolometric luminosity (< 0.1 L_sun). Infrared and (sub-)millimeter observations clearly show an outflow emanating from this source; L1448 IRS2E represents thus far the lowest luminosity source known to be driving a molecular outflow. Comparisons with prestellar cores and Class 0 protostars suggest that L1448 IRS2E is more evolved than prestellar cores but less evolved than Class 0 protostars, i.e., at a stage intermediate between prestellar cores and Class 0 protostars. All these results are consistent with the theoretical predictions of the radiative/magneto hydrodynamical simulations, making L1448 IRS2E the most promising candidate of the first hydrostatic core revealed so far.