. Discovery of Low-ionization Envelopes in the Planetary Nebula NGC 5189 Spatially-resolved Diagnostics from HST Observations Ashkbiz Danehkar, Margarita Karovska, W. Peter Maksym, and Rodolfo Montez Jr. Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138, USA The planetary nebula NGC 5189 shows one of the most spectacular morphology among planetary nebulae. Using high-resolution HST/WFC3 imaging, we discovered the low-ionization structures within 0.3pc × 0.2pc around the central binary system. We used Hα, [O III] , and [S II] emission line images to construct line-ratio diagnostic maps, which allowed us to spatially resolve two distinct low-ionization envelopes within the inner regions. Our diagnostic maps show that highly-ionized gas surrounds these low-ionization envelopes. These envelopes could be a result of a powerful outburst from the central interacting binary, when one of the companions (now a [WO] star) was in its AGB evolutionary stage. Dense material ejected from the progenitor AGB star is likely heated up as propagating along a symmetric axis into the previously expelled material. Our diagnostic mapping using high-resolution imaging can provide a novel approach to detection of low-ionization regions in other planetary nebulae and in other objects including symbiotic systems and expanding envelopes of novae. References Baldwin, Phillips, Terlevich, 1981, PASP, 93, 5 Danehkar et al. 2018, ApJ, [arXiv:1711.11111] Garcia-Rojas et al. 2012, A&A, 538, A54 Kewley et al. 2006, MNRAS, 372, 961 Acknowledgment E-mail: ashkbiz.danehkar@cfa.harvard.edu Spatially-resolved Flux Ratio Maps Resolved Diagnostic Mapping [S II]/Hα flux ratio: high in low-excitation regions [O III]/Hα flux ratio: high in high-excitation regions FIG 1. Image with specific colors of fluorescing sulfur, hydrogen, and oxygen. Credit: NASA/ESA Hubble Space Telescope (Dec 18, 2012). FIG 4. Spatially-resolved diagnostic map of the inner region of NGC 5189. Red and green pixels correspond to low-ionization and photo-ionized regions, respectively. FIG 5. Excitation diagnostic diagram and BPT diagram produced from the 120" × 90" region of NGC 5189 to disentangle fast LISs from photoionized regions. Solid black lines: LINER-like and Seyfert-like boundaries (Kewley+2006), solid red line: nebular photon-shock dividing line (Raga + 2008), star (∗): the mean flux ratios, cross (×): Garcıa-Rojas+2012, and plus (+): Kingsburgh & Barlow (1994). Kingsburgh & Barlow 1994, MNRAS, 271, 257 Maksym et al. 2016, ApJ, 829, 46 Raga et al. 2008, A&A, 489, 1141 Sabin et al. 2012, RMxAA, 48, 165 Main Findings and Future Prospects Two low-ionization envelopes within the inner, ionized gaseous environment, extending over 0.15pc from the central star. Both appear to be expanding along a NE to SW axis. The SW envelope appears smaller than its NE counterpart. These low-ionization envelopes are surrounded by the highly ionized, low-density gas. Our diagnostic methodology is a powerful tool for identifying low-ionization structures in other objects, e.g. complex planetary nebulae, expanding nebulae around symbiotic systems and expanding shells of novae (e.g. V445 Puppis). Diagnostic diagrams based on [O III]/Hα vs. [S II]/Hα ratios Dividing Shock-ionized and Photoionized regions (Raga + 2008) Similar to LINER and Seyfert regions (e.g. Maksym + 2016) in BPT diagrams (Baldwin, Phillips & Terlevich 1981; Kewley + 2006) Shock-ionized Structures within Photoionized Nebula FIG 3. Logarithmic flux [S II]/Hα ratio map of the 120" × 90" region chosen from the HST observations. Two main morphological structures are labelled 120 ” 90” FIG 2. Logarithmic flux [O III]/Hα ratio map of the 120" × 90" region chosen from the HST observations. The contour lines show the boundaries of photo-ionized and low-ionization regions. Two main morphological structures are labelled. We are grateful to Mr. Zoltan Levay and the Hubble Heritage Team who have obtained the NGC5189 HST da