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Zooming on the emerging ionized regions of pPNe with ALMA

C. Sánchez Contreras, D. Tafoya, J. P. Fonfría, J. Alcolea, A. Castro-Carrizo, V. Bujarrabal

TL;DR

This work leverages ALMA's high angular resolution to study the central ionized regions of post-AGB planetary nebulae using mm-wavelength radio recombination lines ($m$RRLs). By mapping M2-9 and CRL 618 in Band 3 and Band 6, and applying 3D non-LTE radiative transfer modeling, the study resolves inner jet-launch zones and constraining physical conditions with unprecedented detail (down to ~20–30 mas, ~15–30 AU). The key findings include a bent ionized jet with a circumbinary disk in M2-9, rapid year-scale variability, HV spots, and a hollow cylindrical ionized core in CRL 618 with speeds up to ~100 km s$^{-1}$, plus a mass-loss rate around $10^{-7}$ M$_$ yr$^{-1}$. These results illuminate jet launching and shaping mechanisms in late stellar evolution and underscore the value of expanding the sample to build statistical understanding of binary-driven outflows in pPNe/yPNe.

Abstract

We report on recent results from our successful and pioneering observational program with ALMA to study emerging ultracom pact HII regions of pre-Planetary Nebulae (pPNe) using mm-wavelength recombination lines (mRRLs) as new optimal tracers. We focus on our study of two poster-child pPNe, namely, M2-9 and CRL618. We reveal the structure and kinematics of the en igmatic inner nebular regions of these objects with an unprecedented angular resolution down to 20-30mas (~15-30AU). For both targets, the ionized central regions are elongated along the main symmetry axis of the large-scale nebulae, consiste nt with bipolar winds, and show notable axial velocity gradients with expansion velocities of up to ~100km/s. The H30a pr ofiles exhibit time variability, reflecting changes in the physical properties and kinematics on scales of a few years. O ur ongoing analysis employs 3D, non-LTE radiative transfer modeling, providing a detailed description of the innermost la yers of these well known pPNe with exceptional clarity.

Zooming on the emerging ionized regions of pPNe with ALMA

TL;DR

This work leverages ALMA's high angular resolution to study the central ionized regions of post-AGB planetary nebulae using mm-wavelength radio recombination lines (RRLs). By mapping M2-9 and CRL 618 in Band 3 and Band 6, and applying 3D non-LTE radiative transfer modeling, the study resolves inner jet-launch zones and constraining physical conditions with unprecedented detail (down to ~20–30 mas, ~15–30 AU). The key findings include a bent ionized jet with a circumbinary disk in M2-9, rapid year-scale variability, HV spots, and a hollow cylindrical ionized core in CRL 618 with speeds up to ~100 km s, plus a mass-loss rate around M yr. These results illuminate jet launching and shaping mechanisms in late stellar evolution and underscore the value of expanding the sample to build statistical understanding of binary-driven outflows in pPNe/yPNe.

Abstract

We report on recent results from our successful and pioneering observational program with ALMA to study emerging ultracom pact HII regions of pre-Planetary Nebulae (pPNe) using mm-wavelength recombination lines (mRRLs) as new optimal tracers. We focus on our study of two poster-child pPNe, namely, M2-9 and CRL618. We reveal the structure and kinematics of the en igmatic inner nebular regions of these objects with an unprecedented angular resolution down to 20-30mas (~15-30AU). For both targets, the ionized central regions are elongated along the main symmetry axis of the large-scale nebulae, consiste nt with bipolar winds, and show notable axial velocity gradients with expansion velocities of up to ~100km/s. The H30a pr ofiles exhibit time variability, reflecting changes in the physical properties and kinematics on scales of a few years. O ur ongoing analysis employs 3D, non-LTE radiative transfer modeling, providing a detailed description of the innermost la yers of these well known pPNe with exceptional clarity.
Paper Structure (8 sections, 3 figures)

This paper contains 8 sections, 3 figures.

Table of Contents

  1. Introduction
  2. Observations
  3. M 2-9 or "The Butterfly Nebula"
  4. An ionized bent jet surrounded by a circumbinary disk
  5. Kinematics of the ionized jet
  6. Non-LTE radiative transfer modeling
  7. CRL 618 or "The Westbrook Nebula"
  8. Concluding remarks

Figures (3)

  • Figure 1: ALMA continuum emission maps of M 2-9 at 232.9 GHz (left) and 95.4 GHz (right) using a circular restoring beam with half power beam width of HPBW=0$.\!\!^{\prime\prime}$04. The level contours are (3$\sigma$)$\times$1.5$^{(i-1)}$ Jy beam$^{-1}$, $i$=1,2,3... The central cross marks the 3 mm continuum surface brightness peak at coordinates J2000 R.A.=17$^{\rm h}$05$^{\rm m}$37$.\!\!^{\rm s}$96679 and Dec.=$-$10$^{\circ }$08$^{\prime}$32$.\!\!^{\prime\prime}$65 (J2000). The yellow arcs, centered at the small yellow cross, represent the broad-waist structure, plausibly a dust disc.
  • Figure 2: Summary of ALMA data of the H30$\alpha$ (top) and H39$\alpha$ (bottom) recombination lines. Left: Integrated line spectrum obtained with ALMA (black lines) and with the IRAM-30 m antenna (grey histogram, CSC+17). Middle: First moment map. Contours going from $V_{\rm LSR}$=45 to 115 km s$^{-1}$ by 5 km s$^{-1}$. The wedge indicates the $V_{\rm LSR}$-color relationship. Right: Position velocity cuts through the center along the wind axis (PA=0$^{\circ }$). Levels are 2.5$\times$(1.3)$^{(i-1)}$ for H30$\alpha$ and 1.5$\times$(1.3)$^{(i-1)}$ for H39$\alpha$ with $i$=1,2,3...
  • Figure 3: Summary of ALMA data for CRL 618. Top-left: Continuum emission map at 232.9 GHz. Top-right: Spectrum of H30$\alpha$ integrated within the emitting area (other lines are also labeled). Bottom: Zeroth and first moment maps (left and right, respectively) of H30$\alpha$. The ellipse at the bottom-left corner of the maps represents the HPBW. The central cross marks the coordinates of the tracking center at R.A.= 04$^{\rm h}$42$^{\rm m}$53$.\!\!^{\rm s}$583 and Dec.= 36$^{\circ }$06$^{\prime}$53$.\!\!^{\prime\prime}$34 (J2000).