Ana M. Teodorescu

Using nmagic to probe the dark matter halo and orbital structure of the X-ray bright, massive elliptical galaxy, NGC 4649

We create dynamical models of the massive elliptical galaxy, NGC 4649, using the N-body made-to-measure code, NMAGIC, and kinematic constraints from long-slit and planetary nebula (PN) data. We explore a range of potentials based on previous determinations from X-ray observations and a dynamical model fitting globular cluster (GC) velocities and a stellar density profile. The X-ray mass distributions are similar in the central region but have varying outer slopes, while the GC mass profile is higher in the central region and on the upper end of the range further out. Our models cannot differentiate between the potentials in the central region, and therefore if non-thermal pressures or multi-phase components are present in the hot gas, they must be smaller than previously inferred. In the halo, we find that the PN velocities are sensitive tracers of the mass, preferring a less massive halo than that derived from the GC mass profile, but similar to one of the mass distributions derived from X-rays. Our results show that the GCs may form a dynamically distinct system, and that the properties of the hot gas derived from X-rays in the outer halo have considerable uncertainties that need to be better understood. Estimating the mass in stars using photometric information and a stellar population mass-to-light ratio, we infer a dark matter mass fraction in NGC 4649 of \tilde0.39 at 1R_e (10.5 kpc) and \tilde0.78 at 4R_e. We find that the stellar orbits are isotropic to mildly radial in the central \tilde6 kpc depending on the potential assumed. Further out, the orbital structure becomes slightly more radial along R and more isotropic along z, regardless of the potential assumed. In the equatorial plane, azimuthal velocity dispersions dominate over meridional velocity dispersions, implying that meridional velocity anisotropy is the mechanism for flattening the stellar system.

Deep spectroscopy of the emission‐line populations in NGC 185★

Because dwarf galaxies are the most abundant type of galaxy, they are crucial for our understanding of the formation and evolution of galaxies. Abundance ratios and their variations as a result of star formation are key constraints in chemical evolution models. Thus, the determination of these abundances in the dwarf galaxies of the Local Universe is extremely important. However, these objects are intrinsically faint, and observational constraints to their evolution can be obtained only for very nearby galaxies. NGC 185 is one of the four brightest dwarf companions of M31. However, unlike the other three – NGC 147, 205 and 221 (M32) – it has an important content of gas and dust. We have obtained deep spectroscopic observations of the Hα emitting population of NGC 185 using the Gemini multi-object spectrograph at the Gemini North telescope. As a result, in addition to the bright planetary nebulae (PNe) previously found in the galaxy and reported in the literature, we have found other, much fainter, PNe. We have then recalculated the electron temperatures and chemical abundances of the brightest PNe and, for the first time, we have derived their electron densities. Our characterization of the population properties of the PNe is interpreted in terms of the chemical evolution of NGC 185, which suggests that it has suffered a significant chemical enrichment within the last ∼8 Gyr. We have also discovered the first symbiotic star in the galaxy and we have determined the properties of a known supernova remnant located close to the centre of NGC 185.

Planetary nebulae: the universal mass–metallicity relation for Local Group dwarf galaxies and the chemistry of NGC 205

Here we study 16 planetary nebulae (PNe) in the dwarf irregular galaxy NGC 205 by using GMOS@Gemini spectra to derive their physical and chemical parameters. The chemical patterns and evolutionary tracks for 14 of our PNe suggest that there are no type I PNe among them. These PNe have an average oxygen abundance of 12+log(O/H)=8.08

A kinematic study of planetary nebulae in the dwarf irregular galaxy IC10

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DISCOVERY, PHOTOMETRY, AND KINEMATICS OF PLANETARY NEBULAE IN M 82*, **

0.28, progenitor masses of 2-2.5M

Planetary nebula spectra in M 60 and M 82

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Planetary nebulae as tracers of the kinematic structure of the starburst galaxy IC 10

and thus were born ~1.0-1.7Gyr ago. Our results are in good agreement with previous PN studies in NGC 205. The present 12+log(O/H) is combined with our previous works and with the literature to study the PN metallicity trends of the Local Group (LG) dwarf galaxies, in an effort to establish the PN luminosity- and mass-metallicity relations (LZR and MZR) for the LG dwarf irregulars (dIrrs) and dwarf spheroidals (dSphs). Previous attempts to obtain such relations failed to provide correct conclusions because were based on limited samples (Richer & McCall 1995; Gon\c{c}calves et al. 2007). As far as we are able to compare stellar with nebular metallicities, our MZR is in very good agreement with the slope of the MZR recently obtained for LG dwarf galaxies using spectroscopic stellar metallicities (Kirby et al. 2013). Actually, we found that both dIrr and dSph galaxies follow the same MZR, at variance with the differences claimed in the past. Moreover our MZR is also consistent with the global MZR of star-forming galaxies, which span a wider stellar mass range (

Planetary nebulae in the elliptical galaxy NGC 4649 (M 60): kinematics and distance redetermination

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The ionization mechanism of NGC 185: how to fake a Seyfert galaxy?

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Deep spectroscopy of the dwarf spheroidal NGC 185

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