[Paper Review] GMOS-IFU Spectroscopy of 167-317 (LV2) Proplyd in Orion

M. J. Vasconcelos, A. H. Cerqueira+3 more|arXiv (Cornell University)|Jun 14, 2005

Astrophysics and Star Formation Studies10 citations

TL;DR

This study presents high-resolution GMOS-IFU spectroscopy of the Orion proplyd 167-317 (LV2), revealing three velocity components: a systemic photoevaporated flow at 28–33 km s⁻¹, a redshifted jet at 80–120 km s⁻¹, and a faint counter-jet at −75 ± 15 km s⁻¹. The authors derive mass loss rates of (6.2 ± 0.6) × 10⁻⁷ M☉ yr⁻¹ for the proplyd and (2.0 ± 0.7) × 10⁻⁸ M☉ yr⁻¹ for the jet, consistent with T Tauri-like outflows.

ABSTRACT

We present high spatial resolution spectroscopic observations of the proplyd 167-317 (LV2) near the Trapezium cluster in the Orion nebula, obtained during the System Verification run of the Gemini Multi Object Spectrograph (GMOS) Integral Field Unit (IFU) at the Gemini South Observatory. We have detected 38 forbidden and permitted emission lines associated with the proplyd and its redshifted jet. We have been able to detect three velocity components in the profiles of some of these lines: a peak with a 28-33 km/s systemic velocity that is associated with the photoevaporated proplyd flow, a highly redshifted component associated with a previously reported jet (which has receding velocities of about 80-120 km/s with respect to the systemic velocity and is spatially distributed to the southeast of the proplyd) and a less obvious, approaching structure, which may possibly be associated with a faint counter-jet with systemic velocity of (-75 +/- 15) km/s. We find evidences that the redshifted jet has a variable velocity, with slow fluctuations as a function of the distance from the proplyd. We present several background subtracted, spatially distributed emission line maps and we use this information to obtain the dynamical characteristics over the observed field. Using a simple model and with the extinction corrected Halpha fluxes, we estimate the mass loss rate for both the proplyd photoevaporated flow and the redshifted microjet, obtaining (6.2 +/- 0.6) x 10^{-7} M_sun/year and (2.0 +/- 0.7) x 10^{-8} M_sun/year, respectively.

Motivation & Objective

• To investigate the kinematic structure of the proplyd 167-317 (LV2) in the Orion Nebula using high-resolution integral field spectroscopy.
• To identify and characterize multiple velocity components in the emission line profiles, including a redshifted jet and a potential counter-jet.
• To estimate the mass loss rates of the photoevaporated proplyd flow and the associated jet using extinction-corrected Hα fluxes and a simple dynamical model.
• To map spatially resolved emission line ratios, such as ([NII]λ6548 + [NII]λ6583)/[NII]λ5754, to infer electron density variations across the source.

Proposed method

• Obtained high spatial and spectral resolution integral field unit (IFU) spectroscopy using the Gemini Multi Object Spectrograph (GMOS) at Gemini South Observatory.
• Constructed background-subtracted, spatially resolved emission line maps for 38 forbidden and permitted lines, including Hα, [O III]λ5007, and [N II] lines.
• Applied extinction correction using the Hβ extinction coefficient (c_Hβ = 0.83) and the relation c_Hβ = Kτ_Hα with K = 0.56 to correct Hα luminosities.
• Used a hemispherical wind model to derive the particle density n₀ and mass loss rate Ẇ from the Hα luminosity, extinction-corrected flux, and ionization front radius r₀ = 7.9 × 10¹⁴ cm.
• Modelled the jet as a spherical blob with radius r_B = 6.7 × 10¹⁴ cm, using its luminosity, velocity (v_j = 180 km s⁻¹), and length (L_j = 4.5 × 10¹⁵ cm) to estimate Ẇ_jet.
• Generated a ([N II]λ6548 + [N II]λ6583)/[N II]λ5754 line ratio map to infer electron density, with values exceeding 10⁵ cm⁻³ in the proplyd region.

Experimental results

Research questions

• RQ1 What are the kinematic components present in the emission line profiles of the proplyd 167-317 (LV2) in Orion?
• RQ2 Is there evidence for a counter-jet associated with the observed redshifted jet in the LV2 system?
• RQ3 What are the mass loss rates for the photoevaporated flow and the jet, and how do they compare to typical T Tauri outflows?
• RQ4 How does the electron density vary spatially across the proplyd and jet structures, as inferred from emission line ratios?
• RQ5 Does the redshifted jet exhibit velocity variability as a function of distance from the ionization front?

Key findings

• Three distinct velocity components were detected in the emission line profiles: a systemic component at 28–33 km s⁻¹, a redshifted jet at 80–120 km s⁻¹, and a faint approaching component at −75 ± 15 km s⁻¹, suggesting a counter-jet.
• The redshifted jet shows variable velocity with slow fluctuations as a function of distance from the proplyd, indicating non-uniform ejection dynamics.
• The mass loss rate for the photoevaporated proplyd flow is estimated at (6.2 ± 0.6) × 10⁻⁷ M☉ yr⁻¹, consistent with previous models of photoevaporation in ionized environments.
• The mass loss rate for the redshifted jet is (2.0 ± 0.7) × 10⁻⁸ M☉ yr⁻¹, comparable to typical T Tauri star jets.
• The ([N II]λ6548 + [N II]λ6583)/[N II]λ5754 line ratio map indicates electron densities above 10⁵ cm⁻³ in the proplyd region, with a subtle enhancement in the jet region.
• The counter-jet is at least four times less intense than the redshifted jet in Hα, supporting its faint and elusive nature despite kinematic evidence.