Abstract
Abstract We analyze data cubes of over 60 emission lines in the HH 32 stellar jet acquired with the Keck Cosmic Web Imager (KCWI). The data cover the less explored blue portion of the spectrum between 3586 and 6351 Å and have both high spectral (R ∼ 10,000) and spatial (≲1″) resolution. The study includes all three major ionization states of oxygen, three Balmer lines, multiple lines of Fe ii and Fe iii, and the first data cubes ever acquired for important unblended diagnostic lines such as He ii λ4686, Ca i λ3933, and Mg i] λ4571. The data cubes generally sort according to excitation and have a relatively continuous progression from the highest-excitation ions (He ii, O iii) through the intermediate-excitation ions (O i and H i) to the lowest-excitation ions (Ca ii and Mg i). Merging the KCWI cubes with Hubble Space Telescope images leads to several new insights about the flow, including evidence for bow shocks, partial bow shocks, spur shocks, Mach disks, jet deflection shocks, a wiggling jet, and potential shock precursors. The most surprising result is that one of the velocity components of Fe ii in the Mach disk suddenly increases in flux relative to other lines by a factor of two, implying that the Mach disk vaporizes dust in the jet. Hence, jets must accelerate or entrain dust to speeds of over 300 km s−1 without destroying the grains.
Highlights
Since their discovery in the 1950s as nebulous emission-line objects in the vicinity of dark clouds, HH objects have become a primary tool for investigating outflows associated with star formation
The project focused on blue lines, which enables the first detailed study of several new ionization states of common elements in stellar jets, including data cubes of Ca II, Mg I, O I, O II, O III, He I, He II, Fe III, Fe II, S II, N II, and three Balmer lines
We found that the overall morphologies of the line emission within these cubes sort remarkably well when grouped according to excitation, defined as a combination of the ionization potential of the element and the energy level of the upper state above ground
Summary
Since their discovery in the 1950s as nebulous emission-line objects in the vicinity of dark clouds, HH objects have become a primary tool for investigating outflows associated with star formation. The observed radial velocities and similarity to supernova remnant spectra led Schwartz (1975) to identify HH objects as radiatively cooled zones in shock fronts, and deep emission-line images revealed that these shocks generally occur within highly collimated jets driven from young stars (e.g., Mundt & Fried 1983) Denser than their surroundings, stellar jets can alter the morphologies of their surroundings radically as they penetrate large distances into their ambient clouds (e.g., McGroarty et al 2004).
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