Far-Infrared Imaging of Post-Asymptotic Giant Branch Stars and (Proto)-Planetary Nebulae With the Akari Far-Infrared Surveyor

Abstract

By tracing the distribution of cool dust in the extended envelopes of post-AGB stars and (proto)planetary nebulae ((P)PNe) we aim to recover, or constrain, the mass loss history experienced by these stars in their recent past. The Far-Infrared Surveyor (FIS) instrument on board the AKARI satellite was used to obtain far-infrared maps for a selected sample of post-AGB stars and (P)PNe. We derived flux densities (aperture photometry) for 13 post-AGB stars and (P)PNe at four far-infrared wavelengths (60, 90, 140, and 160 µm). Radial (azimuthally averaged) profiles are used to investigate the presence of extended emission from cool dust.No (detached) extended emission is detected for any target in our sample at levels significant with respect to background and cirrus emission. Only IRAS 21046+4739 reveals tentative excess emission between 30 and 130 ′′ . Estimates of the total dust and gas mass from the obtained maps indicate that the envelope masses of these stars should be large in order to be detected with the AKARI FIS. Imaging with higher sensitivity and higher spatial resolution is needed to detect and resolve, if present, any cool compact or extended emission associated with these evolved stars.

Physical Properties of the Very Young PN Hen3-1357 (Stingray Nebula) Based on Multiwavelength Observations

“…They interpreted that the far-IR variability in its infrared flux might occur due to recent mass-loss event(s) or evolution of the CSPN. Following the report of Cox et al (2011) and the dust mass ∼4.0(-5) M ⊙ co-existing with the ionized gas by the IRAS data in 1980s, we estimate the dust mass to be 2(-5) M ⊙ in 2006-2007, which is comparable to our derived dust mass of 3.79(-5) M ⊙ within the ionized gas.…”

“…These estimated values are consistent with our derived m g and m d when we stopped the model at r ib . On the dust, Cox et al (2011) found that the AKARI far-IR flux densities are by a factor two lower than predicted from the IRAS data. They interpreted that the far-IR variability in its infrared flux might occur due to recent mass-loss event(s) or evolution of the CSPN.…”

“…AKARI far-IR data would be thermal emission from warm-cold dust. Cox et al (2011) derived an upper limit of the sum of m d and m g = 0.16 M ⊙ within a 3 pc radius using the AKARI/90 µm and a constant dust-to-gas mass ratio (DGR) = 6.25(-3) for O-rich dust, although the measured dust temperature (T d ) is unknown. Using their results, we calculated an upper limit m g = 0.159 M ⊙ and m d = 9.94(-4) M ⊙ , respectively.…”

Circumstellar envelope manifestations in the optical spectra of evolved stars

“…This is primarily true for the physical processes that shape the complex structure of PPN envelopes. Images taken with the Hubble Space Telescope [4,5] and during space IR missions [6] are rarely spherical. Central stars are usually surrounded by envelopes in the form of extended haloes, arcs, lobes, and tori.…”

VISIR-VLT high-resolution study of the extended emission of four obscured post-AGB candidates

“…Infrared surveys (e.g., 2MASS, IRAS, and AKARI) have contributed to the study of objects in the late AGB and early post-AGB stages, providing the first insights into this short transition phase (e.g., García-Lario et al 1997;Jiménez-Esteban et al 2006;Cox et al 2011). Recently, Ramos-Larios et al (2009);Ramos-Larios et al (2012, hereafter RL09 and RL12, respectively) have investigated a sample of heavily obscured post-AGB and PNe candidates selected according to their IRAS colors and the lack of an optical counterpart (Suárez et al 2006) using near-IR JHK and Spitzer IRAC GLIMPSE images, and MSX, AKARI, and IRAS photometric data.…”