scholarly journals Relations between abundance characteristics and rotation velocity for star-forming MaNGA galaxies

2019 ◽  
Vol 623 ◽  
pp. A122 ◽  
Author(s):  
L. S. Pilyugin ◽  
E. K. Grebel ◽  
I. A. Zinchenko ◽  
Y. A. Nefedyev ◽  
J. M. Vílchez
Keyword(s):  
Rotation Velocity ◽  
Effective Radius ◽  
Oxygen Abundance ◽  
Abundance Gradient ◽  
Star Forming ◽  
The Galaxy ◽  
Basic Parameters ◽  
Central Oxygen ◽  
The Mean ◽  
Optical Radius

We derive rotation curves, surface brightness profiles, and oxygen abundance distributions for 147 late-type galaxies using the publicly available spectroscopy obtained by the MaNGA survey. Changes of the central oxygen abundance (O/H)0, the abundance at the optical radius (O/H)R25, and the abundance gradient with rotation velocity Vrot were examined for galaxies with rotation velocities from 90 km s−1 to 350 km s−1. We find that each relation shows a break at Vrot∗ ∼ 200 km s−1. The central (O/H)0 abundance increases with rising Vrot and the slope of the (O/H)0–Vrot relation is steeper for galaxies with Vrot ≲ Vrot∗. The mean scatter of the central abundances around this relation is 0.053 dex. The relation between the abundance at the optical radius of a galaxy and its rotation velocity is similar; the mean scatter in abundances around this relation is 0.081 dex. The radial abundance gradient expressed in dex/kpc flattens with the increase of the rotation velocity. The slope of the relation is very low for galaxies with Vrot ≳ Vrot∗. The abundance gradient expressed in dex/R25 is roughly constant for galaxies with Vrot ≲ Vrot∗, flattens towards Vrot∗, and then again is roughly constant for galaxies with Vrot ≳ Vrot∗. The change of the gradient expressed in terms of dex/hd (where hd is the disc scale length), in terms of dex/Re, d (where Re, d is the disc effective radius), and in terms of dex/Re, g (where Re, g is the galaxy effective radius) with rotation velocity is similar to that for gradient in dex/R25. The relations between abundance characteristics and other basic parameters (stellar mass, luminosity, and radius) are also considered.

scholarly journals Characterizing the radial oxygen abundance distribution in disk galaxies

2019 ◽  
Vol 623 ◽  
pp. A7 ◽  
Author(s):  
I. A. Zinchenko ◽  
A. Just ◽  
L. S. Pilyugin ◽  
M. A. Lara-Lopez
Keyword(s):  
Surface Brightness ◽  
Disk Galaxies ◽  
Abundance Distribution ◽  
Oxygen Abundance ◽  
Abundance Gradient ◽  
Central Surface ◽  
The Galaxy ◽  
Axisymmetric Structures ◽  
Local Oxygen ◽  
Optical Radius

Context. The relation between the radial oxygen abundance distribution (gradient) and other parameters of a galaxy such as mass, Hubble type, and a bar strength, remains unclear although a large amount of observational data have been obtained in the past years. Aims. We examine the possible dependence of the radial oxygen abundance distribution on non-axisymmetrical structures (bar/spirals) and other macroscopic parameters such as the mass, the optical radius R25, the color g − r, and the surface brightness of the galaxy. A sample of disk galaxies from the third data release of the Calar Alto Legacy Integral Field Area Survey (CALIFA DR3) is considered. Methods. We adopted the Fourier amplitude A2 of the surface brightness as a quantitative characteristic of the strength of non-axisymmetric structures in a galactic disk, in addition to the commonly used morphologic division for A, AB, and B types based on the Hubble classification. To distinguish changes in local oxygen abundance caused by the non-axisymmetrical structures, the multiparametric mass–metallicity relation was constructed as a function of parameters such as the bar/spiral pattern strength, the disk size, color index g − r in the Sloan Digital Sky Survey (SDSS) bands, and central surface brightness of the disk. The gas-phase oxygen abundance gradient is determined by using the R calibration. Results. We find that there is no significant impact of the non-axisymmetric structures such as a bar and/or spiral patterns on the local oxygen abundance and radial oxygen abundance gradient of disk galaxies. Galaxies with higher mass, however, exhibit flatter oxygen abundance gradients in units of dex/kpc, but this effect is significantly less prominent for the oxygen abundance gradients in units of dex/R25 and almost disappears when the inner parts are avoided (R >  0.25R25). We show that the oxygen abundance in the central part of the galaxy depends neither on the optical radius R25 nor on the color g − r or the surface brightness of the galaxy. Instead, outside the central part of the galaxy, the oxygen abundance increases with g − r value and central surface brightness of the disk.

scholarly journals Properties of galaxies with an offset between the position angles of the major kinematic and photometric axes

2020 ◽  
Vol 634 ◽  
pp. A26 ◽  
Author(s):  
L. S. Pilyugin ◽  
E. K. Grebel ◽  
I. A. Zinchenko ◽  
J. M. Vílchez ◽  
F. Sakhibov ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Velocity Fields ◽  
Oxygen Abundance ◽  
Star Forming ◽  
Measured Position ◽  
Central Oxygen ◽  
Straight Lines

We derive the photometric, kinematic, and abundance characteristics of 18 star-forming MaNGA galaxies with fairly regular velocity fields and surface brightness distributions and with a large offset between the measured position angles of the major kinematic and photometric axes, ΔPA ≳ 20°. The aim is to examine if there is any other distinctive characteristic common to these galaxies. We found morphological signs of interaction in some (in 11 out of 18) but not in all galaxies. The observed velocity fields show a large variety; the maps of the isovelocities vary from an hourglass-like appearance to a set of straight lines. The position angles of the major kinematic axes of the stellar and gas rotations are close to each other. The values of the central oxygen abundance, radial abundance gradient, and star formation rate are distributed within the intervals defined by galaxies with small (no) ΔPA of similar mass. Thus, we do not find any specific characteristic common to all galaxies with large ΔPA. Instead, the properties of these galaxies are similar to those of galaxies with small (no) ΔPA. This suggests that either the reason responsible for the large ΔPA does not influence other characteristics or the galaxies with large ΔPA do not share a common origin, they can, instead, originate through different channels.

scholarly journals Evidence for azimuthal variations of the oxygen-abundance gradient tracing the spiral structure of the galaxy HCG 91c

2017 ◽  
Vol 601 ◽  
pp. A61 ◽  
Author(s):  
F. P. A. Vogt ◽  
E. Pérez ◽  
M. A. Dopita ◽  
L. Verdes-Montenegro ◽  
S. Borthakur
Keyword(s):  
Spiral Structure ◽  
Oxygen Abundance ◽  
Abundance Gradient ◽  
The Galaxy

scholarly journals A star-forming dwarf galaxy candidate in the halo of NGC 4634

2018 ◽  
Vol 620 ◽  
pp. A29 ◽  
Author(s):  
Y. Stein ◽  
D. J. Bomans ◽  
P. Kamphuis ◽  
E. Jütte ◽  
M. Langener ◽  
...  
Keyword(s):  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Disk Galaxies ◽  
Oxygen Abundance ◽  
Star Forming ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Projected Distance

Context. The halos of disk galaxies form a crucial connection between the galaxy disk and the intergalactic medium. Massive stars, H II regions, or dwarf galaxies located in the halos of galaxies are potential tracers of recent accretion and/or outflows of gas, and are additional contributors to the photon field and the gas phase metallicity. Aims. We investigate the nature and origin of a star-forming dwarf galaxy candidate located in the halo of the edge-on Virgo galaxy NGC 4634 with a projected distance of 1.4 kpc and a Hα star formation rate of ∼4.7 × 10−3 M⊙ yr−1 in order to increase our understanding of these disk-halo processes. Methods. With optical long-slit spectra we measured fluxes of optical nebula emission lines to derive the oxygen abundance 12 + log(O/H) of an H II region in the disk of NGC 4634 and in the star-forming dwarf galaxy candidate. Abundances derived from optical long-slit data and from Hubble Space Telescope (HST) r-band data, Hα data, Giant Metrewave Radio Telescope (GMRT) H I data, and photometry of SDSS and GALEX data were used for further analysis. With additional probes of the luminosity–metallicity relation in the B-band from the Hα-luminosity, the H I map, and the relative velocities, we are able to constrain a possible origin of the dwarf galaxy candidate. Results. The high oxygen abundance (12 + log(O/H) ≈ 8.72) of the dwarf galaxy candidate leads to the conclusion that it was formed from pre-enriched material. Analysis of auxiliary data shows that the dwarf galaxy candidate is composed of material originating from NGC 4634. We cannot determine whether this material has been ejected tidally or through other processes, which makes the system highly interesting for follow up observations.

scholarly journals Population and Evolution of Pulsating A-F Stars

1995 ◽  
Vol 164 ◽  
pp. 364-364
Author(s):  
Jiang Shiyang ◽  
Liu Yanying
Keyword(s):  
White Dwarfs ◽  
Main Sequence ◽  
Rotation Velocity ◽  
Light Variation ◽  
Galactic Rotation ◽  
Strongly Correlated ◽  
The Galaxy ◽  
The Mean ◽  
F Stars ◽  
Rotation Constant

Pulsating A-F variables include all the stellar types listed in teh Table, as well as the pulsating white dwarfs. Stars near the zero-age-main-sequence have faster rotation velocity, which slows as expected with age (Villata 1992) and a smaller amplitude of light variation, so we suggest that rotation velocity be considered in Population classifications. Also, in the Galaxy, the galactic rotation constant A is related to stellar age T by: A(kms−1kpc−1) = (−2.4±0.8)T(109yr) + (32±2) (Kharchenko 1992). The linear rotation velocity is also a function of the Z coordinate of the object inside the Galaxy: the mean Z-gradient is −10kms−1kpc−1 (Malakhova & Petrovskaya, 1992). Thus the population is strongly correlated with the rotation velocity and the evolutionary age.

scholarly journals Azimuthal variations of oxygen abundance profiles in star-forming regions of disc galaxies in EAGLE simulations

2019 ◽  
Vol 491 (4) ◽  
pp. 4894-4901
Author(s):  
Martín Solar ◽  
Patricia B Tissera ◽  
Jose A Hernandez-Jimenez
Keyword(s):  
Stellar Populations ◽  
Chemical Abundances ◽  
Oxygen Abundance ◽  
Star Forming ◽  
Chemical Enrichment ◽  
Numerical Resolution ◽  
Star Forming Regions ◽  
Star Formation Activity ◽  
Large Dispersion ◽  
The Mean

ABSTRACT The exploration of the spatial distribution of chemical abundances in star-forming regions of galactic discs can help us to understand the complex interplay of physical processes that regulate the star formation activity and the chemical enrichment across a galaxy. We study the azimuthal variations of the normalized oxygen abundance profiles in the highest numerical resolution run of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) Project at $z$ = 0. We use young stellar populations to trace the abundances of star-forming regions. Oxygen profiles are estimated along different line of sights from a centrally located observer. The mean azimuthal variation in the EAGLE discs are ∼0.12 ± 0.03 dex $R_{\rm eff}^{-1}$ for slopes and ∼0.12 ± 0.03 dex for the zero-points, in agreement with previous works. Metallicity gradients measured along random directions correlate with those determined by averaging over the whole discs, although with a large dispersion. We find a slight trend for higher azimuthal variations in the disc components of low star-forming and bulge-dominated galaxies. We also investigate the metallicity profiles of stellar populations with higher and lower levels of enrichment than the average metallicity profiles, and we find that high star-forming regions with high metallicity tend to have slightly shallower metallicity slopes compared with the overall metallicity gradient. The simulated azimuthal variations in the EAGLE discs are in agreement with observations, although the large variety of metallicity gradients would encourage further exploration of the metal mixing in numerical simulations.

scholarly journals New Constraints on the 12CO(2 − 1)/(1 − 0) Line Ratio Across Nearby Disc Galaxies

2021 ◽  
Author(s):  
J S den Brok ◽  
D Chatzigiannakis ◽  
F Bigiel ◽  
J Puschnig ◽  
A T Barnes ◽  
...  
Keyword(s):  
Surface Density ◽  
Massive Star ◽  
Formation Rate ◽  
Molecular Gas ◽  
Star Forming ◽  
Large Program ◽  
The Galaxy ◽  
The Mean ◽  
Point To Point ◽  
Disc Galaxies

Abstract Both the CO(2-1) and CO(1-0) lines are used to trace the mass of molecular gas in galaxies. Translating the molecular gas mass estimates between studies using different lines requires a good understanding of the behaviour of the CO(2-1)-to-CO(1-0) ratio, R21. We compare new, high quality CO(1-0) data from the IRAM 30-m EMPIRE survey to the latest available CO(2-1) maps from HERACLES, PHANGS-ALMA, and a new IRAM 30-m M51 Large Program. This allows us to measure R21 across the full star-forming disc of nine nearby, massive, star-forming spiral galaxies at 27″(∼1 − 2 kpc) resolution. We find an average R21 = 0.64 ± 0.09 when we take the luminosity-weighted mean of all individual galaxies. This result is consistent with the mean ratio for disc galaxies that we derive from single-pointing measurements in the literature, $R_{\rm 21, lit}~=~0.59^{+0.18}_{-0.09}$. The ratio shows weak radial variations compared to the point-to-point scatter in the data. In six out of nine targets the central enhancement in R21 with respect to the galaxy-wide mean is of order $\sim 10{-}20\%$. We estimate an azimuthal scatter of ∼20% in R21 at fixed galactocentric radius but this measurement is limited by our comparatively coarse resolution of 1.5 kpc. We find mild correlations between R21 and CO brightness temperature, IR intensity, 70-to-160 μm ratio, and IR-to-CO ratio. All correlations indicate that R21 increases with gas surface density, star formation rate surface density, and the interstellar radiation field.

scholarly journals Recovering the Intrinsic Metallicity Distribution of Elliptical Galaxies

1996 ◽  
Vol 171 ◽  
pp. 353-353
Author(s):  
L. Ciotti ◽  
M. Stiavelli ◽  
A. Braccesi
Keyword(s):  
Elliptical Galaxies ◽  
Effective Radius ◽  
Integrals Of Motion ◽  
Wide Range ◽  
The Galaxy ◽  
Inversion Procedure ◽  
Orbital Mixing ◽  
The Mean ◽  
Simple Inversion ◽  
Metallicity Distribution

We present a simple recipe to derive the metallicity distribution of galaxies as a function of their integrals of the motion. Elliptical galaxies are known to possess metallicity gradients that frequently show variations of a factor of 2 from the center to the effective radius (Peletier, 1989). The observed gradients are the result of projection and orbital mixing. Orbital mixing arises because stars at a given radius may have their apocenters spanning a wide range of radii. Thus, the mean metallicity at any given point inside the galaxy is the result of the metallicity distribution in phase space weighted by the galaxian distribution function. We have proposed (Ciotti, Stiavelli & Braccesi, 1995) a simple inversion procedure allowing one to derive the dependence of metallicity on the integrals of motion for a spherical galaxy. The ideas of this paper can be generalized to oblate two-integrals models following the Hunter & Qian (1993) technique.

scholarly journals Azimuthal variations of gas-phase oxygen abundance in NGC 2997

2018 ◽  
Vol 618 ◽  
pp. A64 ◽  
Author(s):  
I-Ting Ho ◽  
Sharon E. Meidt ◽  
Rolf-Peter Kudritzki ◽  
Brent A. Groves ◽  
Mark Seibert ◽  
...  
Keyword(s):  
Gas Phase ◽  
Spectroscopic Data ◽  
Spiral Galaxies ◽  
Radial Distance ◽  
Optical Data ◽  
Observational Constraints ◽  
Strong Emission ◽  
Oxygen Abundance ◽  
Star Forming ◽  
The Galaxy

The azimuthal variation of the H II region oxygen abundance in spiral galaxies is a key observable for understanding how quickly oxygen produced by massive stars can be dispersed within the surrounding interstellar medium. Observational constraints on the prevalence and magnitude of such azimuthal variations remain rare in the literature. Here, we report the discovery of pronounced azimuthal variations of H II region oxygen abundance in NGC 2997, a spiral galaxy at approximately 11.3 Mpc. Using 3D spectroscopic data from the TYPHOON Program, we have studied the H II region oxygen abundance at a physical resolution of 125 pc. Individual H II regions or complexes are identified in the 3D optical data and their strong emission line fluxes measured to constrain their oxygen abundances. We find 0.06 dex azimuthal variations in the oxygen abundance on top of a radial abundance gradient that is comparable to those seen in other star-forming disks. At a given radial distance, the oxygen abundances are highest in the spiral arms and lower in the inter-arm regions, similar to what has been reported in NGC 1365 using similar observations. We discuss whether the azimuthal variations could be recovered when the galaxy is observed at worse physical resolutions and lower signal-to-noise ratios.

scholarly journals Inner and outer star forming regions over the disks of spiral galaxies

2019 ◽  
Vol 631 ◽  
pp. A23 ◽  
Author(s):  
M. Rodríguez-Baras ◽  
A. I. Díaz ◽  
F. F. Rosales-Ortega
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
Stochastic Effects ◽  
Oxygen Abundance ◽  
Star Forming ◽  
Star Forming Regions ◽  
Two Samples ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Population Effects

Context. The H II regions are all studied employing the same general prescriptions and models, independently of the regions location in the galaxy disk. However, observed discrepancies between physical properties of inner and outer regions may indicate systematic differences in their star formation processes due to the influence of their environments. Aims. Through the analysis of inner and outer H II region observed spectra, we aim to explore possible systematic differences between the physical properties (metallicity, mass, and age) of their ionising clusters in order to study how star formation proceeds in different environments. Methods. We analysed two samples of 725 inner and 671 outer regions, characterised in the first paper of this series. Their functional parameters (oxygen abundances, ionisation parameters, and effective temperatures) were estimated and this parameter grid is employed as input for the computation of 540 Cloudy photoionisation models. Observed regions are compared with model predictions using diagnostic and evolutionary diagrams. Results. Higher metallicities are confirmed for the inner regions, although there are important discrepancies between the diagnostic diagrams. Calibrations based on the N2 index may underestimate inner regions oxygen abundances due to the [N II] saturation at solar metallicities. The degeneracy between the age and ionisation parameter affects oxygen abundance calibrations based on the O3N2 index. Innermost regions seem to have enhanced N/O ratios with respect to the expected values considering secondary production of nitrogen, which indicate an increase in the slope of the relation between N/O and O/H. Ionisation parameter calibrations based on the [S II]/Hα ratio are not valid for inner regions due to the observed bivalued behaviour of this ratio with O/H. Innermost regions have lower [O II]/[O III] ratio values than expected, indicating a possible non-linear relation between u and Z. Composite stellar populations (ionising and non-ionising) are present in both inner and outer regions, with an ionising contribution of around 1%. In considering the effects of evolution and underlying populations, inner regions show larger ionising cluster masses that possibly compose star-forming complexes. The most conservative lower limit for ionising cluster masses of outer regions indicate that they might be affected by stochastic effects. Equivalent widths indicate younger ages for outer regions, but degeneracy between evolution and underlying population effects prevent a quantitative determination. Nebular properties of the H II regions are also derived: inner regions have larger angular sizes, lower filling factors, and larger ionised hydrogen masses. Conclusions. Systematic physical differences are confirmed between ionising clusters of inner and outer H II regions. These differences condition the validity and range of reliability of oxygen abundance and ionisation parameter calibrations commonly applied to the study of H II regions.

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