IFU Spectroscopic Study of the Planetary Nebula Abell 30: Mapping the Ionisation and Kinematic Structure of the Inner Complex

TL;DR

This study uses INTEGRAL/IFU spectroscopy to map the ionisation and kinematic structure of Abell 30's inner hydrogen-poor knot system (J1–J4). Integrated flux maps show ORLs concentrated in the polar knots (J1, J3) and CELs dominating the equatorial knots (J2, J4), while a [O III] temperature diagnostic reveals cool cores (~15,000 K) surrounded by hotter envelopes (>20,000 K), consistent with shock heating or shielding. Velocity-channel and line-fitting analyses uncover non-uniform, ion-dependent kinematics with mean radial velocities varying across knots and ions, and velocity dispersions up to ~140 km s−1, signaling strong turbulence and multiple ejection events. The results, alongside comparisons to Wolf–Rayet binaries and colliding-wind systems, support a binary-driven, shock-laden evolutionary history for A30's inner knots and demonstrate the power of IFU data to disentangle complex ionisation and dynamical structures in planetary nebulae.

Abstract

This work presents integrated flux and velocity channel maps of the planetary nebula Abell 30 (A30) inner knot system. The observations were taken with the INTEGRAL spectrograph at the William Herschel Telescope (WHT). Our IFU data cube partially covers knots J1, J2, and completely covers knots J3, J4 in the system. Optical Recombination Lines of C II, He I, He II, N III, O II and Collisionally Excited Lines of [Ar IV], [Ar V], [N II], [Ne III], [Ne IV], and [O III] were detected. Our integrated flux maps visualise the ionisation structure and the chemical inhomogeneity in the system previously reported by other groups. We find that ORLs are concentrated in the polar region (J1, J3), whereas the equatorial knots (J2, J4) are dominated by CELs. The flux ratio map of the diagnostic [O III] lambda 5007/4363 Angstrom lines reveals the electron temperature distribution, which shows cold cores of 15,000 K in knots J3 and J4 surrounded by a hot outer layer of above 20,000 K. Our channel maps show positive and negative velocity excursions from the systemic value among the ions. Several ions show variation in their velocity structures from their lower-energy-level counterparts, including [Ar IV] and [Ar V], [Ne III] and [Ne IV], and He I and He II. New recurrent velocity structures are identified in the low-density regions where the ions move much faster compared to their surrounding environments. The velocity dispersion measurements highlight extreme turbulence in some of the ions (sigma_vrad approx 140 km/s), consistent with supersonic/hypersonic motion driven by shocks. The forbidden line species [N II] exhibits lower turbulence (sigma_vrad approx 50-60 km/s), tracing denser, less-turbulent gases. Based on our data, we conclude both the ionisation and kinematic studies hint at shock heating and multiple ejection history in the evolutionary pathway of A30.

Figures (20)

• Figure S1: Left panel: Gas clump identification of knots J1--J4 from the outlined regions in white overlaid on the [O III] optical image of the central inner region of A30, adopted from the Hubble Space Telescope WFPC2 Borkowski1995. North is up and East is to the left. Right panel: An integrated flux map of [O III] 5007 Å as an example of the IFU sampled area with a FoV of 12.3$^{\prime\prime}$$\times$ 16$^{\prime\prime}$. Note that the central star (CS) and its surrounding region were masked.
• Figure S2: Integrated flux maps of spectral lines of He I (left) and He II (right). Note the masked central star and background star.
• Figure S3: The same as Figure \ref{['fig:fluxHeI+II']}, but for C II 4267 Å.
• Figure S4: The same as Figure \ref{['fig:fluxHeI+II']} but for [N II] 6548 Å + 6583 Å (left) and N III 4379 Å (right).
• Figure S5: The same as Figure \ref{['fig:fluxHeI+II']} but for (from left to right) O II 4649 Å, [O III] 4363 Å, [O III] 4959 Å + [O III] 5007 Å. Note that the 4363 Å line and the sum of 4959 Å and 5007 Å are shown separately as they carry the electron temperature information (see below).