ALMA Observations of the Extraordinary Carina Pillars: HH 901/902

Abstract: We present Atacama Large Millimeter/Submillimeter Array (ALMA) 1.3 mm continuum and C$^{18}$O(2$-$1), N$2$D$^{+}$(3$-$2), $^{13}$CS(5$-$4), and $^{12}$CO(2$-$1) line sensitive and high angular resolution ($\sim$0.3$''$) observations of the famous carina pillars and protostellar objects HH 901/902. Our observations reveal for the first time, the bipolar CO outflows and the dusty disks (plus envelopes) that are energizing the extended and irradiated HH objects far from the pillars. We find that the masses of the disks$+$envelopes are about 0.1 M$\odot$ and of the bipolar outflows are between 10$^{-3}$ - 10$^{-4}$ M$\odot$, which suggests that they could be low- or maybe intermediate- mass protostars. Moreover, we suggest that these young low-mass stars are likely embedded Class 0/I protostars with high-accretion rates. We also show the kinematics of the gas in the pillars together with their respective gas masses (0.1 -- 0.2 M$\odot$). We estimate that the pillars will be photo-evaporated in 10$^4$ to 10$^5$ years by the massive and luminous stars located in the Trumpler 14 cluster. Finally, given the short photo-evaporated timescales and that the protostars in these pillars are still very embedded, we suggest that the disks inside of the pillars will be quickly affected by the radiation of the massive stars, forming proplyds, like those observed in Orion.

• The paper presents ALMA observations revealing bipolar molecular outflows, disk and envelope masses (~0.1 M{0}{0}{9}), and gas kinematics in the Carina Pillars objects HH 901 and HH 902.
• Observations indicate the protostars driving the outflows are likely low- to intermediate-mass (Class 0/I) with disks and envelopes, undergoing photo-evaporation within 10{0}{0}{b} to 10{0}{0}{b} years.
• These findings imply rapid disk dissipation potentially forming proplyds, provide constraints on progenitor star masses, and enhance understanding of early stellar evolution in high UV environments.

An Overview of ALMA Observations of the Carina Pillars: HH 901/902

The paper explores the observations made using the Atacama Large Millimeter/Submillimeter Array (ALMA) of the Carina star-forming region, focusing on Herbig-Haro (HH) objects 901 and 902. These observations are of notable importance as they provide insights into the dynamics and evolution of star formation in massive star-forming regions exposed to ultraviolet (UV) radiation from nearby massive stars.

Key Observations and Findings

The study employs ALMA's high-angular resolution to capture 1.3 mm continuum data along with molecular line emissions from C$^{18}$O(2-1), N$_2$D$^{+}$(3-2), $^{13}$CS(5-4), and $^{12}$CO(2-1), revealing several features:

1. Bipolar Molecular Outflows: The data reveal, for the first time, bipolar CO outflows associated with HH 901 and HH 902. These outflows are integral in understanding the energetics driving protostellar jet events.
2. Disk and Envelope Masses: The observations detect dusty disks and envelopes energizing the HH objects, estimating masses around 0.1 M$_\odot$. The bipolar outflows have masses ranging between 10$^{-3}$ - 10$^{-4}$ M$_\odot$, suggesting these may be driven by low- to intermediate-mass protostars.
3. Gas Kinematics and Mass: The kinematics of the gas within the pillars are observed, unveiling their respective gas masses (0.1 – 0.2 M$_\odot$). The pillar masses and kinematics help understand the potential fate of these structures under photo-evaporative processes.
4. Photo-Evaporation Timescales: The study predicts that the pillars will undergo photo-evaporation over timescales of 10$^4$ to 10$^5$ years due to UV radiation from the Trumpler 14 cluster. This finding aligns with one of the key interests in observational astronomy – understanding the lifecycle of materials in star-forming regions.

Implications and Future Directions

The results have several implications for the understanding of star formation and the interaction of stellar feedback processes:

• Proplyd Formation: The short photo-evaporation timescales imply that circumstellar disks around the protostars could be rapidly dissipated or shaped into proplyds under the influence of UV radiation, much like those found in the Orion Nebula.
• Constraining Progenitor Masses: The identification of HH objects' progenitor masses has broader implications for theoretical models of stellar evolution and initial mass function dynamics in massive star-forming regions.
• Expansion on Low-Mass Protostar Studies: The observations suggest these protostars are likely in the Class 0/I phase with significant accretion rates, contributing to the growing body of work on early stellar evolution in UV-intense environments.

The paper sets the stage for further research into the role of massive clusters in influencing the immediate environments of nascent stars. Future ALMA observations with higher sensitivity could provide more detailed insights into disk structures and help refine models of disk photo-evaporation in star-forming regions exposed to high levels of UV radiation. The integration of such data with simulations would be instrumental in advancing our understanding of star formation in complex environments.