scholarly journals Carbon, nitrogen and oxygen abundance gradients in M101 and M31

2019 ◽  
Author(s):  
C Esteban ◽  
F Bresolin ◽  
J García-Rojas ◽  
L Toribio San Cipriano
Keyword(s):  
Milky Way ◽  
Spiral Galaxies ◽  
Effective Radius ◽  
H Ii Regions ◽  
Apparent Contradiction ◽  
Radial Gradient ◽  
A Value ◽  
C And N ◽  
M 31 ◽  
Significant Chemical

Abstract We present deep spectrophotometry of 18 H ii regions in the nearby massive spiral galaxies M 101 and M 31. We have obtained direct determinations of electron temperature in all the nebulae. We detect the C ii 4267 Å line in several H ii regions, permitting to derive the radial gradient of C/H in both galaxies. We also determine the radial gradients of O/H, N/O, Ne/O, S/O, Cl/O and Ar/O ratios. As in other spiral galaxies, the C/H gradients are steeper than those of O/H producing negative slopes of the C/O gradient. The scatter of the abundances of O with respect to the gradient fittings do not support the presence of significant chemical inhomogeneities across the discs of the galaxies, especially in the case of M101. We find trends in the S/O, Cl/O and Ar/O ratios as a function of O/H in M101 that can be reduced using Te indicators different from the standard ones for calculating some ionic abundances. The distribution of the N/O ratio with respect to O/H is rather flat in M31, similarly to previous findings for the Milky Way. Using the disc effective radius – Re – as a normalization parameter for comparing gradients, we find that the latest estimates of Re for the Milky Way provide an excess of metallicity in apparent contradiction with the mass-metallicity relation; a value about two times larger might solve the problem. Finally, using different abundance ratios diagrams we find that the enrichment timescales of C and N result to be fairly similar despite their different nucleosynthetic origin.

scholarly journals THE ADF AND THE t2 FORMALISM IN H II REGIONS BASED ON THE UPPER MASS LIMIT OF THE IMF FOR THE MW

2020 ◽  
Vol 56 (2) ◽  
pp. 235-244
Author(s):  
L. Carigi ◽  
A. Peimbert ◽  
M. Peimbert ◽  
G. Delgado-Inglada
Keyword(s):  
Milky Way ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Direct Method ◽  
Formation Rate ◽  
Mass Function ◽  
Initial Mass Function ◽  
H Ii Regions ◽  
Mass Limit ◽  
Better Than

We study in depth the abundance discrepancy problem in H II regions, this time from a different perspective than the usual one: by studying the effect of the upper mass limit (Mup) of the initial mass function (IMF) on the O, C, and He predicted by chemical evolution models for the Milky Way. We use abundances determined with the direct method (DM) and with the temperature independent method (TIM). We compare the predicted abundances at the present time with observations of Orion, M17, and M8 to determine the Mup value of the galactic IMF. From the DM abundances, the models predict an Mup = 25 − 45 M⨀, while from the TIM, CEMs derive an Mup = 70 − 110 M⨀. Spiral galaxies with the stellar mass and star formation rate of the MW are predicted to have an Mup ≈ 100 M⨀. These results support that abundances derived from the TIM are better than those derived from the DM.

scholarly journals Helium abundances and its radial gradient from the spectra of H ii regions and ring nebulae of the Milky Way

2020 ◽  
Vol 496 (3) ◽  
pp. 2726-2742 ◽  
Author(s):  
J E Méndez-Delgado ◽  
C Esteban ◽  
J García-Rojas ◽  
K Z Arellano-Córdova ◽  
M Valerdi
Keyword(s):  
Milky Way ◽  
H Ii Regions ◽  
Abundance Gradient ◽  
Radial Gradient ◽  
Physical Conditions ◽  
The Galaxy ◽  
Ring Nebulae ◽  
Gaia Dr2 ◽  
Disc Galaxies ◽  
Weakly Dependent

ABSTRACT We determine the radial abundance gradient of helium in the disc of the Galaxy from published spectra of 19 H ii regions and ring nebulae surrounding massive O-type stars. We revise the Galactocentric distances of the objects considering Gaia DR2 parallaxes (Gaia Collaboration 2018) and determine the physical conditions and the ionic abundance of He+ in a homogeneous way, using between 3 and 10 He i recombination lines in each object. We estimate the total He abundance of the nebulae and its radial abundance gradient using four different ionization correction factor (ICF; He) schemes. The slope of the gradient is always negative and weakly dependent on the ICF(He) scheme, especially when only the objects with log(η) < 0.9 are considered. The slope values go from −0.0078 to −0.0044 dex kpc−1, consistent with the predictions of chemical evolution models of the Milky Way and chemodynamical simulations of disc galaxies. Finally, we estimate the abundance deviations of He, O, and N in a sample of ring nebulae around Galactic Wolf–Rayet stars, finding a quite similar He overabundance of about +0.24 ± 0.11 dex in three stellar ejecta ring nebulae.

scholarly journals The Origins of Planetary Nebulae in the Inner and Outer Disks of M 31

2016 ◽  
Vol 12 (S323) ◽  
pp. 264-268
Author(s):  
Bruce Balick ◽  
Karen Kwitter ◽  
Romano Corradi ◽  
Rebeca Galera Rosillo ◽  
Richard Henry
Keyword(s):  
Chemical Evolution ◽  
Stellar Population ◽  
Milky Way ◽  
Planetary Nebulae ◽  
Radial Gradient ◽  
M 31 ◽  
Stark Contrast ◽  
Entire Ensemble

AbstractThe planetary nebulae (PNe) of M 31 are receiving considerable attention as probes of its structure and chemical evolution in a galactic environment that is putatively similar to the Milky Way. We have obtained deep spectra for about 30 luminous PNe in M 31’s inner disk and beyond (Rgal < 105 kpc). The entire ensemble of PNe exhibit O/H ~ 2/3 solar with no discernible radial gradient, in stark contrast to the H ii regions of M 31. This suggests that the outer PNe in M 31 formed from a common O-rich ISM at least 5 GY ago. We infer that the outer PNe and the underlying stellar population have little common history in M 31, and that the formation of the O-rich PNe preceded any putative encounter with M 33 ~2–3 Gy ago.

Metallicity gradients in M31, M33, NGC 300, and Milky Way using Argon abundances

2018 ◽  
Vol 14 (A30) ◽  
pp. 268-268
Author(s):  
Sheila N. Flores-Durán ◽  
Miriam Peña
Keyword(s):  
Milky Way ◽  
Planetary Nebulae ◽  
H Ii Regions ◽  
Chemical Abundances ◽  
Local Universe ◽  
Homogeneous Sample ◽  
M 31

AbstractWe studied Planetary Nebulae (PNe) metallicity gradients using Ar abundances. We compared them with H ii regions in the galaxies of the local universe M 31, M 33, NGC 300 and in the Milky Way. Galactocentric radio (RG) and chemical abundances were collected from the literature, carefully selecting an homogeneous sample for each galaxy. In these galaxies, metallicity gradients computed with PNe abundances are flatter than those of H ii regions.

scholarly journals METALLICITY GRADIENTS IN M31, M 33, NGC 300 AND THE MILKY WAY USING ABUNDANCES OF DIFFERENT ELEMENTS

2019 ◽  
Vol 55 (2) ◽  
pp. 255-271 ◽  
Author(s):  
Miriam Peña ◽  
Sheila N. Flores-Durán
Keyword(s):  
Milky Way ◽  
Planetary Nebulae ◽  
Extreme Case ◽  
H Ii Regions ◽  
Type I ◽  
Chemical Abundances ◽  
Homogeneous Sample ◽  
Radial Migration ◽  
Chemical Gradients ◽  
M 31

Metallicity gradients derived from planetary nebulae (PNe) using O, Ne, and Ar abundances are studied and compared to those from H ii regions in the galaxies M 31, M 33, NGC 300 and the Milky Way. Galactocentric radii and chemical abundances were collected from the literature, carefully selecting a homogeneous sample for each galaxy. Metallicity gradients shown by PNe are flatter than those of H ii regions in all cases. The extreme case is M 31 where PN abundances are not related to galactocentric distances and the gradients are consistent with zero. To analyze the evolution of gradients with time we build gradients for Peimbert Type I and non-Type I PNe finding that Type I PNe show steeper gradients than non-Type I PNe and more similar to the ones of H ii regions indicating that the chemical gradients might steepen with time. Alternatively, the flat gradients for old PNe show that radial migration could have an important role in the evolution of galaxies.

scholarly journals The Galactic radial abundance gradients of C, N, O, Ne, S, Cl, and Ar from deep spectra of H ii regions

2020 ◽  
Vol 496 (2) ◽  
pp. 1051-1076 ◽  
Author(s):  
K Z Arellano-Córdova ◽  
C Esteban ◽  
J García-Rojas ◽  
J E Méndez-Delgado
Keyword(s):  
Gas Phase ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Direct Determination ◽  
Atomic Data ◽  
H Ii Regions ◽  
Galactic Disc ◽  
Ionized Gas ◽  
Physical Conditions

ABSTRACT We present a reassessment of the radial abundance gradients of C, N, O, Ne, S, Cl, and Ar in the Milky Way using deep spectra of 33 H ii regions gathered from the literature, covering Galactocentric distances from 6 to 17 kpc. The distances of the objects have been revised using Gaia parallaxes. We recalculate the physical conditions and ionic abundances in an homogeneous way using updated atomic data. All the objects have direct determination of the electron temperature, permitting to derive their precise ionic abundances. We analyse and compare different ICF schemes for each element in order to obtain the most confident total abundances. Due to the revised distances, our results do not support previous claims about a possible flattening of the O/H gradient in the inner Galactic disc. We find that the Galactic N/O gradient is rather flat, in contrast to what has been found in other spiral galaxies. The slope of the gradients of some elements is sensitive to the ICF scheme used, especially in the case of Ne. The dispersion around the fit for the gradients of C, N, O, S, Cl, and Ar is of the order of the typical uncertainties in the determination of the abundances, implying the absence of significant inhomogeneities in the chemical composition of the ionized gas phase of the ISM. We find flat gradients of log(S/O) and log(Cl/O) and very shallow or flat ones for log(Ne/O) and log(Ar/O), consistent with a lockstep evolution of Ne, S, Cl, and Ar with respect to O.

scholarly journals Are ultra-diffuse galaxies Milky Way-sized?

2020 ◽  
Vol 633 ◽  
pp. L3 ◽  
Author(s):  
Nushkia Chamba ◽  
Ignacio Trujillo ◽  
Johan H. Knapen
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Size Range ◽  
Mass Density ◽  
Effective Radius ◽  
Density Profiles ◽  
Gas Density ◽  
Undesirable Consequence ◽  
Definition Of ◽  
Density Threshold

Now almost 70 years since its introduction, the effective or half-light radius has become a very popular choice for characterising galaxy size. However, the effective radius measures the concentration of light within galaxies and thus does not capture our intuitive definition of size which is related to the edge or boundary of objects. For this reason, we aim to demonstrate the undesirable consequence of using the effective radius to draw conclusions about the nature of faint ultra-diffuse galaxies (UDGs) when compared to dwarfs and Milky Way-like galaxies. Instead of the effective radius, we use a measure of galaxy size based on the location of the gas density threshold required for star formation. Compared to the effective radius, this physically motivated definition places the sizes much closer to the boundary of a galaxy. Therefore, considering the sizes and stellar mass density profiles of UDGs and regular dwarfs, we find that the UDGs have sizes that are within the size range of dwarfs. We also show that currently known UDGs do not have sizes comparable to Milky Way-like objects. We find that, on average, UDGs are ten times smaller in extension than Milky Way-like galaxies. These results show that the use of size estimators sensitive to the concentration of light can lead to misleading results.

scholarly journals Globular Cluster and Galaxy Formation: M31, the Milky Way, and Implications for Globular Cluster Systems of Spiral Galaxies

2004 ◽  
Vol 614 (1) ◽  
pp. 158-166 ◽  
Author(s):  
David Burstein ◽  
Yong Li ◽  
Kenneth C. Freeman ◽  
John E. Norris ◽  
Michael S. Bessell ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Globular Cluster ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Cluster Systems

Chemo-dynamical signatures in simulated Milky Way-like galaxies

2017 ◽  
Vol 12 (S330) ◽  
pp. 263-264
Author(s):  
Alessandro Spagna ◽  
Anna Curir ◽  
Marco Giammaria ◽  
Mario G. Lattanzi ◽  
Giuseppe Murante ◽  
...  
Keyword(s):  
Milky Way ◽  
Galactic Plane ◽  
Dynamical Evolution ◽  
Thin Disk ◽  
Disk Galaxy ◽  
Radial Gradient ◽  
Heating Mechanism ◽  
Disk Evolution ◽  
Inside Out

AbstractWe have investigated the chemo-dynamical evolution of a Milky Way-like disk galaxy, AqC4, produced by a cosmological simulation integrating a sub-resolution ISM model. We evidence a global inside-out and upside-down disk evolution, that is consistent with a scenario where the “thin disk” stars are formed from the accreted gas close to the galactic plane, while the older “thick disk” stars are originated in situ at higher heights. Also, the bar appears the most effective heating mechanism in the inner disk. Finally, no significant metallicity-rotation correlation has been observed, in spite of the presence of a negative [Fe/H] radial gradient.

scholarly journals Several evolutionary channels for bright planetary nebulae

2015 ◽  
Vol 11 (S317) ◽  
pp. 344-345 ◽  
Author(s):  
Michael G. Richer ◽  
Marshall L. McCall
Keyword(s):  
Spectral Properties ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Planetary Nebulae

AbstractThe populations of bright planetary nebulae in the discs of spirals appear to differ in their spectral properties from those in ellipticals and the bulges of spirals. The bright planetary nebulae from the bulge of the Milky Way are entirely compatible with those observed in the discs of spiral galaxies. The similarity might be explained if the bulge of the Milky Way evolved secularly from the disc, in which case the bulge should be regarded as a pseudo-bulge.

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