29 research outputs found
Planetary nebulae and the chemical evolution of the galactic bulge: new abundances of older objects
In view of their nature, planetary nebulae have very short lifetimes, and the
chemical abundances derived so far have a natural bias favoring younger
objects. In this work, we report physical parameters and abundances for a
sample of old PNe located in the galactic bulge, based on low dispersion
spectroscopy secured at the SOAR telescope using the Goodman Spectrograph. The
new data allow us to extend our database including older, weaker objects that
are at the faint end of the planetary nebula luminosity function (PNLF). The
results show that the abundances of our sample are lower than those from our
previous work. Additionally, the average abundances of the galactic bulge do
not follow the observed trend of the radial abundance gradient in the disk.
These results are in agreement with a chemical evolution model for the Galaxy
recently developed by our group.Comment: 2 pages, 2 figures, to appear in proceedings of the IAU Symposium
283: "Planetary Nebulae: An Eye to the Future", Eds.: A. Manchado, L.
Stanghellini and D. Schoenberne
The Milky Way disk radial gradient from planetary nebulae reveled by Gaia
Radial abundance gradients in the Galactic disc are one of the most important observational constraints to study
the chemical evolution of the Milky Way galaxy and also other galaxies in the universe. The radial gradient is the
result of many physical processes that occur since the formation of the Galaxy, as e.g. the infalling gas to form the
disc, the star formation history, radial gas flows and the radial migration of stars. Planetary nebulae (PNe) are the
offspring of low and intermediate-mass stars consisting of an expanding, glowing shell of ionised gas ejected from
red giant stars late in their lives. They have very intense optical emission lines and some elements observed in PNe
are not modified during the progenitor star evolution, making then important tools to probe the Galactic chemical
evolution. However, PNe distances are subject of great uncertainties, since, unlike main sequence stars, these
objects do not have a physical parameter that is direct dependent of the distance. In this work, we have used Gaia
DR3 database in order to derive reliable distances for a sample of 294 Galactic PNe. The radial gradient from the O,
S, Ar and Ne are computed using the new distances in the radial range from 3 to 15 kpc. The results are consistent
with a flatter gradient than previously found and with a change of the slope around 8 kpc, which coincides with the
Milky Way corotation radius
Galactic chemical evolution: Stellar yields and the initial mass function
We present a set of 144 Galactic chemical evolution models applied to a Milky Way analogue, computed using four sets of low+intermediate star nucleosynthetic yields, six massive star yield compilations, and six functional forms for the initial mass function. A comparison is made between a grid of multiphase chemical evolution models computed with these yield combinations and empirical data drawn from the Milky Way's disc, including the solar neighbourhood. By means of a χ2 methodology, applied to the results of these multiphase models, the best combination of stellar yields and initial mass function capable of reproducing these observations is identified
Planetary nebulae in the inner Milky Way
New abundances of planetary nebulae located towards the bulge of the Galaxy
are derived based on observations made at LNA (Brazil). We present accurate
abundances of the elements He, N, S, O, Ar, and Ne for 56 PNe located towards
the galactic bulge. The data shows a good agreement with other results in the
literature, in the sense that the distribution of the abundances is similar to
those works. From the statistical analysis performed, we can suggest a
bulge-disk interface at 2.2 kpc for the intermediate mass population, marking
therefore the outer border of the bulge and inner border of the disk.Comment: 2 pages, 1 figure, uses iaus.cls, in press, IAU Symp. 265, Chemical
abundances in the Universe: Connecting the first Stars to Planets, Ed. K.
Cunha, M. Spite, B. Barbu
The role of gas infall in the evolution of disc galaxies
Spiral galaxies are thought to acquire their gas through a protracted infall
phase resulting in the inside-out growth of their associated discs. For field
spirals, this infall occurs in the lower density environments of the cosmic
web. The overall infall rate, as well as the galactocentric radius at which
this infall is incorporated into the star-forming disc, plays a pivotal role in
shaping the characteristics observed today. Indeed, characterising the
functional form of this spatio-temporal infall in-situ is exceedingly
difficult, and one is forced to constrain these forms using the present day
state of galaxies with model or simulation predictions. We present the infall
rates used as input to a grid of chemical evolution models spanning the mass
spectrum of discs observed today. We provide a systematic comparison with
alternate analytical infall schemes in the literature, including a first
comparison with cosmological simulations. Identifying the degeneracies
associated with the adopted infall rate prescriptions in galaxy models is an
important step in the development of a consistent picture of disc galaxy
formation and evolution.Comment: 12 pages, 12 figures, MNRAS, accepte
The role of gas infall in the evolution of disc galaxies
Spiral galaxies are thought to acquire their gas through a protracted infall phase resulting in the inside-out growth of their associated discs. For field spirals, this infall occurs in the lower density environments of the cosmic web. The overall infall rate, as well as the galactocentric radius at which this infall is incorporated into the star-forming disc, plays a pivotal role in shaping the characteristics observed today. Indeed, characterising the functional form of this spatio-temporal infall in-situ is exceedingly difficult, and one is forced to constrain these forms using the present day state of galaxies with model or simulation predictions. We present the infall rates used as input to a grid of chemical evolution models spanning the mass spectrum of discs observed today. We provide a systematic comparison with alternate analytical infall schemes in the literature, including a first comparison with cosmological simulations. Identifying the degeneracies associated with the adopted infall rate prescriptions in galaxy models is an important step in the development of a consistent picture of disc galaxy formation and evolution