Cosmological simulations predict that early-type galaxies (ETGs) are the results of extended mass accretion histories. The latter are characterized by different numbers of mergers, mergers’ mass ratios and gas fractions, and timing. Depending on the sequence and nature of these mergers that follow the first phase of the in-situ star formation, these accretion histories may lead to ETGs that have low or high mass halos, and that rotate fast or slow. Since the stellar halos maintain the fossil records of the events that led to their formation, a discontinuity may be in place between the inner regions of ETGs and their outer halos, because the time required for the halos’ stars to exchange their energies and momenta is very long compared with the age of these systems. Exquisite deep photometry and extended spectroscopy for significant samples of ETGs are then used to quantify the occurrence and significance of such a transition in the galaxies’ structural and kinematical parameters. Once this transition radius is measured, its dependency with the effective radius of the galaxies’ light distribution and total stellar masses can be investigated. Such correlations can then be compared with the predictions of accreted, i.e. ex-situ vs. in-situ components from cosmological simulations to validate such models.

The carbon-rich AGB star V Hya is believed to be in the very brief transition phase between the AGB and a planetary nebula (PN). Using HST/STIS, we previously found a high-velocity (> 200 kms−1) jet or blob of gas ejected only a few years ago from near (< 0.3 arcsec or 150 AU) the star (Sahai et al. 2003, Sahai et al. 2016). From multi-epoch high-resolution spectroscopy we found time-variable high-velocity absorption features in the CO 4.6 μm vibration-rotation lines of V Hya (Sahai et al. 2009). Modeling shows that these are produced in compact clumps of outflowing gas with significant radial temperature gradients consistent with strong shocks. Here, we present very high resolution (∼100 milliarcsecond) imaging of the central region of V Hya using the coronagraphic mode of the Gemini Planet Imager (GPI) in the 1 μm band and spectral-spatial imaging of 4.6 μm CO 1-0 transitions using the Phoenix spectrometer. We report the detection of a compact central dust disk from GPI, and molecular emission from the Phoenix observations at relatively larger scales. We discuss models for the central structures in V Hya, in particular disks and outflows, using these and complementary images in the optical and radio.

In the final stages of stellar evolution low- to intermediate-mass stars lose their envelope in increasingly massive stellar winds. Such winds affect the interstellar medium and the galactic chemical evolution as well as the circumstellar envelope where planetary nebulae form subsequently. Characteristics of this mass loss depend on both stellar properties and properties of gas and dust in the wind formation region. In this paper we present an approach towards studies of mass loss using both observations and models, focussing on the stage where the stellar envelope is nearly empty of mass. In a recent study we measure the mass-loss evolution, and other properties, of four planetary nebulae in the Galactic disk. Specifically we use the method of integral field spectroscopy on faint halos, which are found outside the much brighter central parts of a planetary nebula. We begin with a brief comparison between our and other observational methods to determine mass-loss rates in order to illustrate how they differ and complement each other. An advantage of our method is that it measures the gas component directly requiring no assumptions of properties of dust in the wind. Thereafter we present our observational approach in more detail in terms of its validity and its assumptions. In the second part of this paper we discuss capabilities and assumptions of current models of stellar winds. We propose and discuss improvements to such models that will allow meaningful comparisons with our observations. Currently the physically most complete models include too little mass in the model domain to permit a formation of winds with as high mass-loss rates as our observations show.

A concise summary of the recent international workshop held in honour of the career of Agnès Acker is presented together with a brief exposition of her productive career in the study of Planetary Nebulae, the expelled, ionised outer shrouds of dying stars.

We have obtained a large sample of PN with accurately determined helium abundances, as well as abundances of several heavy elements. The nebulae are located in the solar neighbourhood, in the galactic bulge, disk and anticentre, and in the Magellanic Clouds. The abundances are analyzed both in terms of the nucleosynthesis of intermediate mass stars and the chemical evolution of the host galaxies. In particular, correlations between the He/H ratio and the abundances of N and O are used as constraints of the nucleosynthetic processes occurring in the progenitor stars.

New helium abundances of planetary nebulae located towards the bulge of the Galaxy were derived, based on observations made at OPD (Brazil). We present accurate helium abundances for 56 PNe located towards the galactic bulge. The data show good agreement with other results in the literature, in the sense that the distribution of the abundances is similar to previous works. Furthermore, the radial helium gradient is extended towards the galactic center. The results show that no trend can be identified when comparing the internal gradient (R ≤ 4 kpc) to the whole galactic disk.

We present total element abundances based upon newly acquired spectrophotometry of a sample of $>$120 Galactic PNe. We continue to explore the use of the near-IR [S III] features to determine S$^{+2}$ abundances and to improve total extrapolated sulfur - a useful metallicity tracer. With this compilation we explore abundance patterns in PNe that reveal signatures of stellar evolution and nucleosynthesis as well as larger-scale galactic chemical evolution.

A better understanding of the nature of the molecular and ionized gas envelopes of planetary nebulae (PNe) is important both to our understanding of their contribution to the ISM and to the evolution of PNe themselves. Using HST's unprecedented resolution and sensitivity for near-IR observations, we are studying the distribution and intensity of molecular gas emission from PNe.

The San Pedro Mártir Kinematic Catalogue of Planetary Nebulae aims at providing detailed kinematic information for galactic planetary nebulae (PNe) and bright PNe in the Local Group. The database provides long-slit, Echelle spectra and images where the location of the slits on the nebula are indicated. As a tool to help interpret the 2D line profiles or position-velocity data, an atlas of synthetic emission line spectra accompanies the Catalogue. The atlas has been produced with the code SHAPE and contains synthetic spectra for all the main morphological groups for a wide range of spatial orientations and slit locations over the nebula.

New Planetary Nebulae (PNe) were discovered through an [O III] 5007 Å emission line survey in the Galactic bulge region with $l >$ 0$^{\circ}$. We detected 240 objects, including 44 new PNe. Deep H$\alpha +$[N II] CCD images as well as low resolution spectra were obtained for the new PNe in order to study them in detail. Preliminary photo–ionization models of the new PNe with Cloudy resulted in first estimates of the physical parameters and abundances. They are compared to the abundances of Galactic PNe.

The alpha elements O, Ne, Mg, Si, S, Cl, and Ar are produced together in massive stars and their abundances are expected to evolve in lockstep. Both H II regions and planetary nebulae serve as interstellar probes of alpha element abundances. We have measured abundances for the alpha elements O, Ne, S, Cl, and Ar in over 130 Galactic Types I and II and halo PNe in a consistent manner from our own optical (3600–9600Å) spectra (Henry, Kwitter, & Balick 2004). Figure 1 is a plot of Ne vs. O for a combined dataset containing H II regions, blue compact galaxies, and our sample of planetary nebulae. All object types appear to be consistent with the expected linear relation between Ne and O. Similar plots of Cl and Ar vs. O show the same behavior. However, S vs. O is an exception.