Exploring the differences of integrated and spatially resolved analysis using integral field unit data: the case of Abell 14

Abstract

We present a new approach to study planetary nebulae using integral field spectroscopy. VLT@VIMOS datacube of the planetary nebula Abell 14 is analysed in three different ways by extracting: (i) the integrated spectrum, (ii) 1-dimensional simulated long slit spectra for different position angles and (iii) spaxel-by-spaxel spectra. These data are used to built emission-line diagnostic diagrams and explore the ionization structure and excitation mechanisms combining data from 1-and 3-dimensional photoionization models. The integrated and 1D simulated spectra are suitable for developing diagnostic diagrams, while the spaxel spectra can lead to misinterpretation of the observations. We find that the emission-line ratios of Abell 14 are consistent with UV photo-ionized emission; however, there are some pieces of evidence of an additional thermal mechanism. The chemical abundances confirm its previous classification as a Type I planetary nebula, without spatial variation. We find, though, variation in the ionization correction factors (ICFs) as a function of the slit position angle. The star at the geometric centre of Abell 14 has an A5 spectral type with an effective temperature of T eff = 7909±135 K and surface gravity log(g) = 1.4±0.1 cm s −2 . Hence, this star cannot be responsible for the ionization state of the nebula. Gaia parallaxes of this star yield distances between 3.6 and 4.5 kpc in good agreement with the distance derived from a 3-dimensional photoionization modelling of Abell 14, indicating the presence of a binary system at the centre of the planetary nebula.

SATELLITE: Application to Planetary Nebulae IFU Data

“…SATELLITE was used in the analysis of four Galactic PNe so far: Abell 14 (VIMOS, [7]), Hen 2-108 (VIMOS, Miranda-Marques et al 2021 submitted), NGC 7009, and NGC 6778 (MUSE, Akras et al 2021 submitted). Below, we briefly present some of the results obtained for each one.…”

“…Integral field spectroscopy has changed the way we study extended ionized nebulae, such as PNe galaxies or H II regions. However, the comparison between the spaxel-by-spaxel analysis of IFU and the traditional long-slit spectroscopy or 1D modelling is not straightforward [7,28]. A new Python code, namely SATELLITE, was recently developed (Akras et al 2021, submitted) to carry out 1D (pseudo-slits) and 2D (spaxel-by-spaxel) spectroscopic analyses of the line maps provide by IFUs.…”

“…Therefore, Abell 14 was an ideal nebula to apply and test the SATELLITE code and in the end explore the line ratios in both spatial directions through the 2D analysis module, as well as for the specific slit orientations through the specific slits analysis module in the code (see, [7]). [N I] λ5200/Hβ ratio was found to be in agreement with the result reported by [14].…”

“…The development of state-of-the-art spectrographs equipped with integral field units (IFU) overcome this limitation. Integral field spectroscopy (IFS) has changed the way we approach and study extended ionized nebulae, such as PNe, e.g., [7,8], H II regions [9], galaxies [10], and supernova remnants [11], simultaneously providing spectroscopic characterization in both spatial directions. However, the results from IFUs are not directly comparable with the results from the traditional long-slit spectroscopy or the predictions from 1D photoionization and shock modelling.…”

Morphologies of Wolf–Rayet Planetary Nebulae Based on IFU Observations

“…A number of integral field unit (IFU) spectrographs on modest telescopes, such as the Wide Field Spectrograph (WiFeS [24,25]) on the Australian National University (ANU) 2.3-m telescope have made it possible to constrain the kinematic and ionization properties of several PNe [26][27][28][29][30][31][32]. Moreover, the Multi Unit Spectroscopic Explorer (MUSE) and the VIsible Multi-Object Spectrograph (VIMOS) on the European Southern Observatory's (ESO) Very Large Telescope (VLT) have recently enabled the constraint of the ionization structures of some PNe [33][34][35][36]. IFU spectroscopy allows us to spatially resolve the physical and kinematic properties of PNe, which is an important step toward understanding their morphological features in different ionization stratification layers.…”