16 research outputs found
Bimodal chemical evolution of the Galactic disk and the Barium abundance of Cepheids
In order to understand the Barium abundance distribution in the Galactic disk
based on Cepheids, one must first be aware of important effects of the
corotation resonance, situated a little beyond the solar orbit. The thin disk
of the Galaxy is divided in two regions that are separated by a barrier
situated at that radius. Since the gas cannot get across that barrier, the
chemical evolution is independent on the two sides of it. The barrier is caused
by the opposite directions of flows of gas, on the two sides, in addition to a
Cassini-like ring void of HI (caused itself by the flows). A step in the
metallicity gradient developed at corotation, due to the difference in the
average star formation rate on the two sides, and to this lack of communication
between them. In connection with this, a proof that the spiral arms of our
Galaxy are long-lived (a few billion years) is the existence of this step. When
one studies the abundance gradients by means of stars which span a range of
ages, like the Cepheids, one has to take into account that stars, contrary to
the gas, have the possibility of crossing the corotation barrier. A few stars
born on the high metallicity side are seen on the low metallicity one, and
vice-versa. In the present work we re-discuss the data on Barium abundance in
Cepheids as a function of Galactic radius, taking into account the scenario
described above. The [Ba/H] ratio, plotted as a function of Galactic radius,
apparently presents a distribution with two branches in the external region
(beyond corotation). One can re-interpret the data and attribute the upper
branch to the stars that were born on the high metallicity side. The lower
branch, analyzed separately, indicates that the stars born beyond corotation
have a rising Barium metallicity as a function of Galactic radius.Comment: 6 pages, 7 figures, Proceedings of IAU Symposium 29
The Brazilian Tunable Filter Imager for the SOAR telescope
This paper presents a new Tunable Filter Instrument for the SOAR telescope.
The Brazilian Tunable Filter Imager (BTFI) is a versatile, new technology,
tunable optical imager to be used in seeing-limited mode and at higher spatial
fidelity using the SAM Ground-Layer Adaptive Optics facility at the SOAR
telescope. The instrument opens important new science capabilities for the SOAR
community, from studies of the centers of nearby galaxies and the insterstellar
medium to statistical cosmological investigations. The BTFI takes advantage of
three new technologies. The imaging Bragg Tunable Filter concept utilizes
Volume Phase Holographic Gratings in a double-pass configuration, as a tunable
filter, while a new Fabry-Perot (FP) concept involves technologies which allow
a single FP etalon to act over a large range of interference orders and
spectral resolutions. Both technologies will be in the same instrument.
Spectral resolutions spanning the range between 25 and 30,000 can be achieved
through the use of iBTF at low resolution and scanning FPs beyond R ~2,000. The
third new technologies in BTFI is the use of EMCCDs for rapid and cyclically
wavelength scanning thus mitigating the damaging effect of atmospheric
variability through data acquisition. An additional important feature of the
instrument is that it has two optical channels which allow for the simultaneous
recording of the narrow-band, filtered image with the remaining (complementary)
broad-band light. This avoids the uncertainties inherent in tunable filter
imaging using a single detector. The system was designed to supply tunable
filter imaging with a field-of-view of 3 arcmin on a side, sampled at 0.12" for
direct Nasmyth seeing-limited area spectroscopy and for SAM's visitor
instrument port for GLAO-fed area spectroscopy. The instrument has seen first
light, as a SOAR visitor instrument. It is now in comissioning phase.Comment: accepted in PAS
Gaia GraL: Gaia DR2 Gravitational Lens Systems. VII. XMM-Newton Observations of Lensed Quasars
© 2022. The Author(s). Published by the American Astronomical Society. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.3847/1538-4357/ac4476We present XMM-Newton X-ray observations of nine confirmed lensed quasars at 1 ≲ z ≲ 3 identified by the Gaia Gravitational Lens program. Eight systems are strongly detected, with 0.3-8.0 keV fluxes F 0.3-8.0 ≳ 5 ×10-14 erg cm-2 s-1. Modeling the X-ray spectra with an absorbed power law, we derive power-law photon indices and 2-10 keV luminosities for the eight detected quasars. In addition to presenting sample properties for larger quasar population studies and for use in planning for future caustic-crossing events, we also identify three quasars of interest: a quasar that shows evidence of flux variability from previous ROSAT observations, the most closely separated individual lensed sources resolved by XMM-Newton, and one of the X-ray brightest quasars known at z > 3. These sources represent the tip of the discoveries that will be enabled by SRG/eROSITA.Peer reviewe
Gaia GraL: Gaia DR2 gravitational lens systems – VIII. A radio census of lensed systems
© 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/We present radio observations of 24 confirmed and candidate strongly lensed quasars identified by the Gaia Gravitational Lenses working group. We detect radio emission from eight systems in 5.5 and 9 GHz observations with the Australia Telescope Compact Array (ATCA), and 12 systems in 6 GHz observations with the Karl G. Jansky Very Large Array (VLA). The resolution of our ATCA observations is insufficient to resolve the radio emission into multiple lensed images, but we do detect multiple images from 11 VLA targets. We have analysed these systems using our observations in conjunction with existing optical measurements, including measuring offsets between the radio and optical positions for each image and building updated lens models. These observations significantly expand the existing sample of lensed radio quasars, suggest that most lensed systems are detectable at radio wavelengths with targeted observations, and demonstrate the feasibility of population studies with high-resolution radio imaging.Peer reviewe
Gaia GraL: Gaia DR2 Gravitational Lens Systems. VIII. A radio census of lensed systems
We present radio observations of 24 confirmed and candidate strongly lensed
quasars identified by the Gaia Gravitational Lenses (GraL) working group. We
detect radio emission from 8 systems in 5.5 and 9 GHz observations with the
Australia Telescope Compact Array (ATCA), and 12 systems in 6 GHz observations
with the Karl G. Jansky Very Large Array (VLA). The resolution of our ATCA
observations is insufficient to resolve the radio emission into multiple lensed
images, but we do detect multiple images from 11 VLA targets. We have analysed
these systems using our observations in conjunction with existing optical
measurements, including measuring offsets between the radio and optical
positions, for each image and building updated lens models. These observations
significantly expand the existing sample of lensed radio quasars, suggest that
most lensed systems are detectable at radio wavelengths with targeted
observations, and demonstrate the feasibility of population studies with high
resolution radio imaging
CARAVANA "LUAR DO SERTÃO": UNINDO POLOS DO MNPEF PARA O ENSINO DE FISICA E ASTRONOMIA NO NORDESTE
In this work, we present the formation of a group composed by MNPEF/Northeast hubs dedicated to the Teaching and Dissemination of Physics and Astronomy, joining local efforts for a collaborative regional action of at least two years. Thus, celebrating the 50th anniversary of the Apollo missions and the current Artemis Project, in which the first woman and the first black person will walk on the moon, we will present scientific dissemination actions proposed in public spaces to promote critical thinking and inclusion. Starting from telescopic observations of our satellite and parallel activities, we will present refutations to conspiracy theories that deny that the humanity's were on the Moon and the spherical shape of the Earth. In partnership with the MNPEF hubs, a module on “Astronomy and Space Exploration”, according the BNCC and the New High School Teaching it will be offered, turning our students, multipliers. With this capillarity and logistics together with the Regional Education Departments, we will prepare teachers for nighttime observations and training activities, with their students and the population. Materials and strategies are already defined, and will impact 30 northeastern cities, sharing a dialogic and pleasant experience between local and scientific knowledge. Approved in first place at CNPq 36/2022 call for proposals, the project should leave as a legacy the inter-institutional and community connection; materials that favor scientific literacy for training multipliers and; resources that push the extension, teaching and research activities of our network, which we intend to expand on a national scale.Apresentamos neste trabalho a formação de um grupo de polos do MNPEF/Nordeste dedicado ao Ensino e Divulgação da Física e Astronomia, somando esforços locais para uma ação regional colaborativa de pelo menos dois anos. Assim, celebrando os 50 anos das missões Apollo e o atual Projeto Artemis, em que a primeira mulher e a primeira pessoa negra pisarão na Lua, apresentaremos as ações de divulgação científica propostas em espaços públicos para promover os sensos crítico e de inclusão. Partindo de observações telescópicas itinerantes de nosso satélite e atividades paralelas, apresentaremos refutações às teorias de conspiração que negam a ida da humanidade à Lua e o formato esférico da Terra. Em parceria com os polos do MNPEF, um módulo sobre “Astronomia e Exploração Espacial”, à luz da BNCC e do Novo Ensino Médio será ofertado aos nossos discentes, tornando-os polos multiplicadores. Com esta capilaridade e logística em parcerias feitas com as Secretarias de Educação, prepararemos os professores para as observações noturnas e atividades formativas, com a participação de seus estudantes e da população. Materiais e estratégias da ação já estão definidos, e impactarão as comunidades de 30 municípios nordestinos, compartilhando uma experiência dialógica e lúdica entre saberes locais e científicos. Aprovado em primeira colocação na chamada 36/2022 do CNPq, o projeto deverá deixar como legado as conexões interinstitucionais e comunitárias; materiais que favoreçam o letramento científico e a formação de multiplicadores e; recursos que alavanquem as atividades de extensão, ensino e pesquisa de nossa rede, que pretendemos ampliar a uma escala nacional
Gaia GraL: Gaia DR2 Gravitational Lens Systems. VII. XMM-Newton Observations of Lensed Quasars
Abstract
We present XMM-Newton X-ray observations of nine confirmed lensed quasars at 1 ≲ z ≲ 3 identified by the Gaia Gravitational Lens program. Eight systems are strongly detected, with 0.3–8.0 keV fluxes F
0.3−8.0 ≳ 5 ×10−14 erg cm−2 s−1. Modeling the X-ray spectra with an absorbed power law, we derive power-law photon indices and 2–10 keV luminosities for the eight detected quasars. In addition to presenting sample properties for larger quasar population studies and for use in planning for future caustic-crossing events, we also identify three quasars of interest: a quasar that shows evidence of flux variability from previous ROSAT observations, the most closely separated individual lensed sources resolved by XMM-Newton, and one of the X-ray brightest quasars known at z > 3. These sources represent the tip of the discoveries that will be enabled by SRG/eROSITA.</jats:p
Implications of intrauterine protein malnutrition on prostate growth, maturation and aging
Aims Maternal malnutrition by low protein diet is associated with an increased incidence of metabolic disorders and decreased male fertility in adult life. This study aimed to assess the impact of maternal protein malnutrition (MPM) on prostate growth, tissue organization and lesion incidence with aging. Main methods Wistar rat dams were distributed into two groups, which were control (NP; fed a normal diet containing 17% protein) or a restricted protein diet (RP, fed a diet containing 6% protein) during gestation. After delivery all mothers and offspring received a normal diet. Biometrical parameters, hormonal levels and prostates were harvested at post-natal days (PND) 30, 120 and 360. Key findings MPM promoted low birth weight, decreased ano-genital distance (AGD) and reduced androgen plasma levels of male pups. Prostatic lobes from RP groups presented reduced glandular weight, epithelial cell height and alveolar diameter. The epithelial cell proliferation and collagen deposition were increased in RP group. Incidences of epithelial dysplasia and prostatitis were higher in the RP offspring than in the NP offspring at PND360. Significance Our findings show that MPM delays prostate development, growth and maturation until adulthood, probably as a result of low testosterone stimuli. The higher incidence of cellular dysplasia and prostatitis suggests that MPM increases prostate susceptibility to diseases with aging. © 2013 Elsevier Inc
Gaia GraL: Gaia DR2 Gravitational Lens Systems. VII. XMM-Newton Observations of Lensed Quasars
We present XMM-Newton X-ray observations of nine confirmed lensed quasars at identified by the Gaia Gravitational Lens program. Eight systems are strongly detected, with 0.3--8.0 keV fluxes . Modeling the X-ray spectra with an absorbed power law, we derive power law photon indices and 2--10 keV luminosities for the eight detected quasars. In addition to presenting sample properties for larger quasar population studies and for use in planning for future caustic crossing events, we also identify three quasars of interest: a quasar that shows evidence of flux variability from previous ROSAT observations, the most closely-separated individual lensed sources resolved by XMM-Newton, and one of the X-ray brightest quasars known at . These sources represent the tip of discovery that will be enabled by SRG/eROSITA