Near- and mid-IR morphology of the water maser emitting planetary nebula K 3-35

Abstract

The shaping process of planetary nebulae (PNe) takes place during the short transition from the asymptotic giant branch (AGB) phase to the white dwarf stage. The young PN K 3-35 represents a unique case where a small-sized water maser ring has been linked to the launch of collimated outflows that shape the nebula. The contrasting optical and radio continuum morphologies of K 3-35 indicate that they disclose different structural components that are apparently unconnected. To bridge the gap between optical and radio continuum observations, we present here new broadband and narrowband near-and mid-IR images of K 3-35. These images, and their comparison with optical and radio continuum images, are revealing. The radio continuum and mid-IR images are dominated by a compact source at the core of K 3-35 whose emission gives evidence of very dense ionized material embedded within a dust cocoon. The emission from the core, obscured at optical wavelengths, is faintly detected in the K s band. We suggest that the dust may shield the water molecules at the inner ring from the central star ionizing radiation. The precessing collimated outflows, very prominent in radio continuum, are also detected in mid-IR, very particularly in the [S iv] image. The mid-IR emission from these outflows consist mostly of ionized material, although the broadband filter at 11.85 μm seems to imply that a small amount of dust may be carried out by the outflow. The interactions of these outflows with the nebular shell result in shocks that excite the emission of H 2 as well as low-excitation lines from ionized species, such as [N ii] at the tips of the outflows.

Polarization properties of OH emission in planetary nebulae

“…OHPNe do not seem to form an homogeneous group (Uscanga et al 2012). While objects such as IRAS 17347−3139 or K3-35 are optically obscured and/or compact in size (≃ 10000 AU, de Gregorio-Monsalvo et al 2004;Blanco et al 2014), others like NGC 6302 are optically bright and very extended (≃ 1 pc, Szyszka, Zijlstra, & Walsh 2011), and thus, they are probably more evolved PNe. Therefore not all OHPNe seem to strictly conform to their expected nature as extremely young PNe, and some other process may sustain OH emission for a longer time than previously assumed.…”

The reactivation of water maser emission in the planetary nebula IRAS 18061--2505 through a born-again episode

“…• 6) and high extinction at visible wavelengths of these objects, although the amount of extinction is quite different among H2O-PNe. For instance, IRAS18061 is completely visible (now, but not in ∼1951.6, Figure 4), K 3-35 is highly extincted towards its equatorial region but its bipolar lobes are clearly visible (e.g., Blanco et al 2014), and IRAS 15103−5754 is not optically visible. A possible shortcoming for an intermediate-mass MS progenitor in IRAS18061 is the small ionised nebular mass.…”

“…H2O-PNe are revealing important aspects of PN formation. Interaction between jets and the AGB envelope may excite water masers in young PNe, as suggested by Miranda et al (2001a) to explain the water masers at the tips of the precessing jets in K 3-35 (see also Miranda et al 2007;Tafoya et al 2011;Blanco et al 2014). Magnetic fields have been detected in some H2O-PNe via OH maser polarisation (Miranda et al 2001a;Gómez et al 2009Gómez et al , 2016Qiao et al 2016;Hou & Gao 2020).…”

“…Figure4), K 3-35 is highly extincted towards its equatorial region but its bipolar lobes are clearly visible (e.g.,Blanco et al 2014), and IRAS 15103−5754 is not optically visible. A possible shortcoming for an intermediate-mass MS progenitor in IRAS18061 is the small ionised nebular mass.…”