2,252 research outputs found
Spectroscopic Observations of Planetary Nebulae in the Northern Spur of M31
We present spectroscopy of three planetary nebulae (PNe) in the Northern Spur
of the Andromeda Galaxy (M31) obtained with the Double Spectrograph on the 5.1
m Hale Telescope at the Palomar Observatory. The samples are selected from the
observations of Merrett et al. Our purpose is to investigate formation of the
substructures of M31 using PNe as a tracer of chemical abundances. The [O III]
4363 auroral line is detected in the spectra of two objects, enabling
temperature determinations. Ionic abundances are derived from the observed
collisionally excited lines, and elemental abundances of nitrogen, oxygen, and
neon as well as sulphur and argon are estimated. Correlations between oxygen
and the alpha-element abundance ratios are studied, using our sample and the
M31 disk and bulge PNe from the literature. In one of the three PNe, we
observed relatively higher oxygen abundance compared to the disk sample in M31
at similar galactocentric distances. The results of at least one of the three
Northern Spur PNe might be in line with the proposed possible origin of the
Northern Spur substructure of M31, i.e. the Northern Spur is connected to the
Southern Stream and both substructures comprise the tidal debris of the
satellite galaxies of M31.Comment: 5 tables, 17 figures; accepted for publication in Ap
Photoionization models of the CALIFA HII regions. I. Hybrid models
Photoionization models of HII regions require as input a description of the
ionizing SED and of the gas distribution, in terms of ionization parameter U
and chemical abundances (e.g. O/H and N/O). A strong degeneracy exists between
the hardness of the SED and U, which in turn leads to high uncertainties in the
determination of the other parameters, including abundances. One way to resolve
the degeneracy is to fix one of the parameters using additional information.
For each of the ~ 20000 sources of the CALIFA HII regions catalog, a grid of
photoionization models is computed assuming the ionizing SED being described by
the underlying stellar population obtained from spectral synthesis modeling.
The ionizing SED is then defined as the sum of various stellar bursts of
different ages and metallicities. This solves the degeneracy between the shape
of the ionizing SED and U. The nebular metallicity (associated to O/H) is
defined using the classical strong line method O3N2 (which gives to our models
the status of "hybrids"). The remaining free parameters are the abundance ratio
N/O and the ionization parameter U, which are determined by looking for the
model fitting [NII]/Ha and [OIII]/Hb. The models are also selected to fit
[OII]/Hb. This process leads to a set of ~ 3200 models that reproduce
simultaneously the three observations.
We find that the regions associated to young stellar bursts suffer leaking of
the ionizing photons, the proportion of escaping photons having a median of
80\%. The set of photoionization models satisfactorily reproduces the electron
temperature derived from the [OIII]4363/5007 line ratio. We determine new
relations between the ionization parameter U and the [OII]/[OIII] or
[SII]/[SIII] line ratios. New relations between N/O and O/H and between U and
O/H are also determined.
All the models are publicly available on the 3MdB database.Comment: Accepted for publication in A&
Telehealth: The future is now in allergy practice
info:eu-repo/semantics/publishedVersio
What do asthmatic patients think about telemedicine visits?
Introduction. Due to the Coronavirus disease 2019 (COVID-19) outbreak and the national emergency state, virtual visits were implemented as an alternative to in-person visits. With this study we aimed to establish asthma patients' general satisfaction with the quality of health care provided by virtual visits (phone or video calls). Materials and methods. A questionnaire (9 questions) was published on the Facebook page of the Portuguese Association of Asthmatics. It was available online for general self-reported asthmatic patients to answer during one month, starting on 11st May 2020. The survey only allowed one answer per registered user. Results. Fifty-five responses were obtained. Patients were satisfied with communication with providers (> 88%); nevertheless, one-half evaluated the virtual visit as inferior when compared to in-person visits. About one third attributed a classification of 6 or less (0-10 scale, 0 being the worst and 10 the best consultation possible), but still most of the patients would either recommend it or use this kind of medical visits in the future, even outside the actual pandemic context. Patients also referred some important limitations, as lack of physical examination and the fact that the medical visit was more impersonal. Only 27% had technical issues accessing virtual visits. Positive aspects were also named, such as virtual visits being practical and avoiding the need to move to the hospital. Discussion and conclusions. Our survey revealed that small changes could further increase patients' satisfaction, adherence and confidence in telemedicine. Although presenting some limitations, virtual visits seem to be generally well accepted by asthmatic patients and it might be a good alternative for in-person visits, at leastin such difficult times when social distancing is recommended.info:eu-repo/semantics/publishedVersio
Developing Faculty to Provide University Students With Improved Learning Experiences
The article addresses the importance of incorporating faculty development as a key priority of higher education institutions. A literature review and some face-to-face and online interviews were conducted at various U.S. institutions, to identify common and best practices regarding this important matter. The article offers some ideas about what is done, and how it is done, to help faculty be ready for the challenging role they need to play: to be effective developers of a diverse student body that meets the evolving needs of industry and that utilizes technological tools that never existed before
Resolving galaxies in time and space: II: Uncertainties in the spectral synthesis of datacubes
In a companion paper we have presented many products derived from the
application of the spectral synthesis code STARLIGHT to datacubes from the
CALIFA survey, including 2D maps of stellar population properties and 1D
averages in the temporal and spatial dimensions. Here we evaluate the
uncertainties in these products. Uncertainties due to noise and spectral shape
calibration errors and to the synthesis method are investigated by means of a
suite of simulations based on 1638 CALIFA spectra for NGC 2916, with
perturbations amplitudes gauged in terms of the expected errors. A separate
study was conducted to assess uncertainties related to the choice of
evolutionary synthesis models. We compare results obtained with the Bruzual &
Charlot models, a preliminary update of them, and a combination of spectra
derived from the Granada and MILES models. About 100k CALIFA spectra are used
in this comparison.
Noise and shape-related errors at the level expected for CALIFA propagate to
0.10-0.15 dex uncertainties in stellar masses, mean ages and metallicities.
Uncertainties in A_V increase from 0.06 mag in the case of random noise to 0.16
mag for shape errors. Higher order products such as SFHs are more uncertain,
but still relatively stable. Due to the large number statistics of datacubes,
spatial averaging reduces uncertainties while preserving information on the
history and structure of stellar populations. Radial profiles of global
properties, as well as SFHs averaged over different regions are much more
stable than for individual spaxels. Uncertainties related to the choice of base
models are larger than those associated with data and method. Differences in
mean age, mass and metallicity are ~ 0.15 to 0.25 dex, and 0.1 mag in A_V.
Spectral residuals are ~ 1% on average, but with systematic features of up to
4%. The origin of these features is discussed. (Abridged)Comment: A&A, accepte
The Calar Alto Legacy Integral Field Area Survey: extended and remastered data release
This paper describes the extended data release of the Calar Alto Legacy
Integral Field Area (CALIFA) survey (eDR). It comprises science-grade quality
data for 895 galaxies obtained with the PMAS/PPak instrument at the 3.5 m
telescope at the Calar Alto Observatory along the last 12 years, using the V500
setup (3700-7500{\AA}, 6{\AA}/FWHM) and the CALIFA observing strategy. It
includes galaxies of any morphological type, star-formation stage, a wide range
of stellar masses (10 10 Msun ), at an average redshift of
0.015 (90\% within 0.005z0.05). Primarily selected based on the
projected size and apparent magnitude, we demonstrate that it can be volume
corrected resulting in a statistically limited but representative sample of the
population of galaxies in the nearby Universe. All the data were homogeneous
re-reduced, introducing a set of modifications to the previous reduction. The
most relevant is the development and implementation of a new
cube-reconstruction algorithm that provides with an (almost) seeing-limited
spatial resolution (FWHM PSF 1.0").To illustrate the usability and
quality of the data, we extracted two aperture spectra for each galaxy (central
1.5" and fully integrated), and analyze them using pyFIT3D. We obtain a set of
observational and physical properties of both the stellar populations and the
ionized gas, that have been compared for the two apertures, exploring their
distributions as a function of the stellar masses and morphologies of the
galaxies, comparing with recent results in the literature. DATA RELEASE:
http://ifs.astroscu. unam.mx/CALIFA_WEB/public_html/Comment: 30 pages, 26 figures, accepted for publishing in the MNRA
Resolving the age bimodality of galaxy stellar populations on kpc scales
Galaxies in the local Universe are known to follow bimodal distributions in
the global stellar populations properties. We analyze the distribution of the
local average stellar-population ages of 654,053 sub-galactic regions resolved
on ~1-kpc scales in a volume-corrected sample of 394 galaxies, drawn from the
CALIFA-DR3 integral-field-spectroscopy survey and complemented by SDSS imaging.
We find a bimodal local-age distribution, with an old and a young peak
primarily due to regions in early-type galaxies and star-forming regions of
spirals, respectively. Within spiral galaxies, the older ages of bulges and
inter-arm regions relative to spiral arms support an internal age bimodality.
Although regions of higher stellar-mass surface-density, mu*, are typically
older, mu* alone does not determine the stellar population age and a bimodal
distribution is found at any fixed mu*. We identify an "old ridge" of regions
of age ~9 Gyr, independent of mu*, and a "young sequence" of regions with age
increasing with mu* from 1-1.5 Gyr to 4-5 Gyr. We interpret the former as
regions containing only old stars, and the latter as regions where the relative
contamination of old stellar populations by young stars decreases as mu*
increases. The reason why this bimodal age distribution is not inconsistent
with the unimodal shape of the cosmic-averaged star-formation history is that
i) the dominating contribution by young stars biases the age low with respect
to the average epoch of star formation, and ii) the use of a single average age
per region is unable to represent the full time-extent of the star-formation
history of "young-sequence" regions.Comment: 17 pages, 11 figures, MNRAS accepte
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