4,283 research outputs found
Characterizing the radial oxygen abundance distribution in disk galaxies
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
CALIFA DR3 is considered. 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 SDSS bands, and central surface brightness of the disk.
The gas-phase oxygen abundance gradient is determined by using the R
calibration. 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. 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.Comment: 11 pages, 6 figures; accepted for publication in A&
Study of star-forming galaxies in SDSS up to redshift 0.4: I. Metallicity evolution
The chemical composition of the gas in galaxies versus cosmic time provides a
very important tool for understanding galaxy evolution. Although there are many
studies at high redshift, they are rather scarce at lower redshifts. However,
low redshift studies can provide important clues about the evolution of
galaxies, furnishing the required link between local and high redshift
universe. In this work we focus on the metallicity of the gas of star-forming
galaxies at low redshift, looking for signs of chemical evolution.
To analyze the metallicity contents star-forming galaxies of similar
luminosities and masses at different redshifts. With this purpose, we present a
study of the metallicity of relatively massive (log(M_star/M_sun)>10.5) star
forming galaxies from SDSS--DR5 (Sloan Digital Sky Survey--Data Release 5),
using different redshift intervals from 0.04 to 0.4.
We used data processed with the STARLIGHT spectral synthesis code, correcting
the fluxes for dust extinction, estimating metallicities using the R_23 method,
and segregating the samples with respect to the value of the
[NII]6583/[OII]3727 line ratio in order to break the R_23 degeneracy selecting
the upper branch. We analyze the luminosity and mass-metallicity relations, and
the effect of the Sloan fiber diameter looking for possible biases.
By dividing our redshift samples in intervals of similar magnitude and
comparing them, significant signs of metallicity evolution are found.
Metallicity correlates inversely with redshift: from redshift 0 to 0.4 a
decrement of ~0.1 dex in 12+log(O/H) is found.Comment: 11 pages, 9 figures, Accepted for publication in A&
Searching for Milky Way twins: Radial abundance distribution as a strict criterion
We search for Milky Way-like galaxies among a sample of approximately 500
galaxies. The characteristics we considered of the candidate galaxies are the
following: stellar mass M_star, optical radius R_25, rotation velocity V_rot,
central oxygen abundance (O/H)_0, and abundance at the optical radius
(O/H)_R25. If the values of R_25 and M_star of the galaxy were close to that of
the Milky Way, then the galaxy was referred to as a structural Milky Way
analogue (sMWA). The oxygen abundance at a given radius of a galaxy is defined
by the evolution of that region, and we then assumed that the similarity of
(O/H)_0 and (O/H)_R25 in two galaxies suggests a similarity in their evolution.
If the values of (O/H)_0 and (O/H)_R25 in the galaxy were close to that of the
Milky Way, then the galaxy was referred to as an evolutionary Milky Way
analogue (eMWA). If the galaxy was simultaneously an eMWA and sMWA, then the
galaxy was considered a Milky Way twin. We find that the position of the Milky
Way on the (O/H)_0 - (O/H)_R25 diagram shows a large deviation from the general
trend in the sense that the (O/H)_R25 in the Milky Way is appreciably lower
than in other galaxies of similar (O/H)_0. This feature of the Milky Way
evidences that its (chemical) evolution is not typical. We identify four
galaxies (NGC~3521, NGC~4651, NGC~2903, and MaNGA galaxy M-8341-09101) that are
simultaneously sMWA and eMWA and can therefore be considered as Milky Way
twins. In previous studies, Milky Way-like galaxies were selected using
structural and morphological characteristics, that is, sMWAs were selected. We
find that the abundances at the centre and at the optical radius (evolutionary
characteristics) provide a stricter criterion for selecting real Milky Way
twinsComment: Accepted to Astronomy and Astrophysics, 28 pages, 13 figure
Two types of distribution of the gas velocity dispersion of MaNGA galaxies
The distribution of the gas velocity dispersion sigma across the images of
1146 MaNGA galaxies is analyzed. We find that there are two types of
distribution of the gas velocity dispersion across the images of galaxies: (i)
the distributions of 909 galaxies show a radial symmetry with or without the
sigma enhancement at the center (R distribution) and (ii) distributions with a
band of enhanced sigma along the minor axis in the images of 159 galaxies with
or without the sigma enhancement at the center (B distribution) The sigma
distribution across the images of 78 galaxies cannot be reliable classified. We
select 806 galaxies with the best defined characteristics (this sample includes
687 galaxies with R distribution and 119 galaxies with B distribution) and
compare the properties of galaxies with R and B distributions. We find that the
median value of the gas velocity dispersion sigma_m in galaxies with B
distribution is higher by around 5 km/s, on average, than that of galaxies with
R distribution. The optical radius R_25 of galaxies with B distribution is
lower by around 0.1 dex, on average, than that of galaxies with similar masses
with R distribution. Thus the properties of a galaxy are related to the type of
distribution of the gas velocity dispersion across its image. This suggests
that the presence of the band of the enhanced gas velocity dispersion can be an
indicator of a specific evolution (or a specific stage in the evolution) of a
galaxy.Comment: 5 pages, 4 figures, accepted to Astron.Astrophys. arXiv admin note:
text overlap with arXiv:2005.1274
The metallicity - redshift relations for emission-line SDSS galaxies: examination of the dependence on the star formation rate
We analyse the oxygen abundance and specific star formation rates (sSFR)
variations with redshift in star-forming SDSS galaxies of different masses. We
find that the maximum value of the sSFR, sSFRmax, decreases when the stellar
mass, Ms, of a galaxy increases, and decreases with decreasing of redshift. The
sSFRmax can exceed the time-averaged sSFR by about an order of magnitude for
massive galaxies. The metallicity - redshift relations for subsamples of
galaxies with sSFR = sSFRmax and with sSFR = 0.1sSFRmax coincide for massive
(log(Ms/Mo) > 10.5, with stellar mass Ms in solar units) galaxies and differ
for low-mass galaxies. This suggests that there is no correlation between
oxygen abundance and sSFR in massive galaxies and that the oxygen abundance
correlates with the sSFR in low-mass galaxies. We find evidence in favour of
that the irregular galaxies show, on average, higher sSFR and lower oxygen
abundances than the spiral galaxies of similar masses and that the mass -
metallicity relation for spiral galaxies differs slightly from that for
irregular galaxies. The fact that our sample of low-mass galaxies is the
mixture of spiral and irregular galaxies can be responsible for the dependence
of the metallicity - redshift relation on the sSFR observed for the low-mass
SDSS galaxies. The mass - metallicity and luminosity - metallicity relations
obtained for irregular SDSS galaxies agree with corresponding relations for
nearby irregular galaxies with direct abundance determinations. We find that
the aperture effect does not make a significant contribution to the redshift
variation of oxygen abundances in SDSS galaxies.Comment: 14 pages, 7 figures, accepted for publication in the MNRA
Galaxy And Mass Assembly (GAMA): a deeper view of the mass, metallicity and SFR relationships
A full appreciation of the role played by gas metallicity (Z), star formation rate (SFR) and stellar mass (M*) is fundamental to understanding how galaxies form and evolve. The connections between these three parameters at different redshifts significantly affect galaxy evolution, and thus provide important constraints for galaxy evolution models. Using data from the Sloan Digital Sky Survey–Data Release 7 (SDSS–DR7) and the Galaxy and Mass Assembly (GAMA) surveys, we study the relationships and dependences between SFR, Z and M*, as well as the Fundamental Plane for star-forming galaxies. We combine both surveys using volume-limited samples up to a redshift of z ≈ 0.36. The GAMA and SDSS surveys complement each other when analysing the relationships between SFR, M* and Z. We present evidence for SFR and metallicity evolution to z ∼ 0.2. We study the dependences between SFR, M*, Z and specific SFR (SSFR) on the M*–Z, M*–SFR, M*–SSFR, Z–SFR and Z–SSFR relations, finding strong correlations between all. Based on those dependences, we propose a simple model that allows us to explain the different behaviour observed between low- and high-mass galaxies. Finally, our analysis allows us to confirm the existence of a Fundamental Plane, for which M* = f(Z, SFR) in star-forming galaxies
Circumnuclear regions of different BPT types in star-forming MaNGA galaxies: AGN detectability
We consider the circumnuclear regions of MaNGA galaxies. The spectra are
classified as AGN-like, HII-region-like (or SF-like), and intermediate (INT)
spectra according to their positions on the BPT diagram. There are the
following four configurations of the radiation distributions in the
circumnuclear regions: 1) AGN+INT, the innermost region of the AGN-like
radiation is surrounded by a ring of radiation of the intermediate type; 2)
INT, the central area of radiation of the intermediate type; 3) SF+INT, the
inner region of the HII-region-like radiation is surrounded by a ring of
radiation of the intermediate type; and 4) SF, the HII-region-like radiation
only. The LINERS of configurations 1 and 2 are examined. The spaxel spectra of
the LINERs form a sequences on the BPT diagram. The line ratios change smoothly
with radius, from AGN-like at the center to HII-region-like at larger
distances. This is in agreement with the paradigm that the LINERs are excited
by AGN activity. The AGN and INT radiation in the circumnuclear region is
accompanied by an enhanced gas velocity dispersion, s_g. The radius of the area
of the AGN and INT radiation is similar to the radius of the area with enhanced
s_g, and the central s_g,c correlates with the luminosity of the AGN+INT area.
We assume that the gas velocity dispersion can serve as an indicator of the AGN
activity. The values of s_g,c for the SF-type centers partly overlap with those
of the AGN-type centers. We find that there is a demarcation line between the
positions of the AGN-type and SF-type objects on the s_g,c - central Halpha
surface brightness diagram.Comment: 17 pages, 14 figures, accepted for publication in the A&
Calibration-based abundances in the interstellar gas of galaxies from slit and IFU spectra
In this work we make use of available Integral Field Unit (IFU) spectroscopy
and slit spectra of several nearby galaxies. The pre-existing empirical R and S
calibrations for abundance determinations are constructed using a sample of HII
regions with high quality slit spectra. In this paper, we test the
applicability of those calibrations to the IFU spectra. We estimate the
calibration-based abundances obtained using both the IFU and the slit
spectroscopy for eight nearby galaxies. The median values of the slit and IFU
spectra-based abundances in bins of 0.1 in fractional radius Rg (normalized to
the optical radius) of a galaxy are determined and compared. We find that the
IFU and the slit spectra-based abundances obtained through the R calibration
are close to each other, the mean value of the differences of abundances is
0.005 dex and the scatter in the differences is 0.037 dex for 38 datapoints.
The S calibration can produce systematically underestimated values of the IFU
spectra-based abundances at high metallicities, the mean value of the
differences is -0.059 dex for 21 datapoints, while at lower metallicities the
mean value of the differences is -0.018 dex and the scatter is 0.045 dex for 36
data points. This evidences that the R calibration produces more consistent
abundance estimations between the slit and the IFU spectra than the S
calibration. We find that the same calibration can produce close estimations of
the abundances using IFU spectra obtained with different spatial resolution and
different spatial samplings. This is in line with the recent finding that the
contribution of the diffuse ionized gas to the large aperture spectra of HII
regions has a secondary effect.Comment: 15 pages, 14 figures, accepted to the Astronomy and Astrophysic
Galaxy And Mass Assembly (GAMA): growing up in a bad neighbourhood - how do low-mass galaxies become passive?
Both theoretical predictions and observations of the very nearby Universe
suggest that low-mass galaxies (log[M/M]<9.5) are likely
to remain star-forming unless they are affected by their local environment. To
test this premise, we compare and contrast the local environment of both
passive and star-forming galaxies as a function of stellar mass, using the
Galaxy and Mass Assembly survey. We find that passive fractions are higher in
both interacting pair and group galaxies than the field at all stellar masses,
and that this effect is most apparent in the lowest mass galaxies. We also find
that essentially all passive log[M/M]<8.5 galaxies are
found in pair/group environments, suggesting that local interactions with a
more massive neighbour cause them to cease forming new stars. We find that the
effects of immediate environment (local galaxy-galaxy interactions) in forming
passive systems increases with decreasing stellar mass, and highlight that this
is potentially due to increasing interaction timescales giving sufficient time
for the galaxy to become passive via starvation. We then present a simplistic
model to test this premise, and show that given our speculative assumptions, it
is consistent with our observed results.Comment: 20 pages, 12 figures, Accepted to MNRA
Physician–Patient Communication About Sexual Functioning in Patients with Multiple Sclerosis
Sexual dysfunction is quite common among individuals with multiple sclerosis (MS); however, severity of dysfunction alone does not account for the tremendous variation in sexual satisfaction across individuals living with MS. Individual characteristics, relationships with intimate partners, and environmental factors all likely contribute to the multidimensional experience of sexual satisfaction. Health care provider variables, including how one communicates with providers about sexual concerns, may also be influential. The purpose of this study was to examine factors that are associated with patients’ sex-related communications with their MS physicians and to overall patient sexual satisfaction. Individuals in an MS clinic (n = 73) completed a survey packet which included measures of physical and mental health, sexual dysfunction, sexual satisfaction, sex communication, health care provider relationships, and health care satisfaction. Findings suggest that while more than half of patients with MS reported experiencing sexual dysfunction, only a third of patients indicated addressing their sexual concerns with their physician during the past year. Interestingly, the frequency of communication about sexual concerns was associated with satisfaction with physician variables, whereas selfefficacy for these interactions was associated with emotional health variables. These results indicate that when considering interventions to increase confidence for communication and frequency of communication that differing factors may be taken into account
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