pinecone/core-2020-05-10-deduplication huggingface dataset:
Dynamical and chemical evolution of the thin disc

Our detailed analytic local disc model (JJ-model) quantifies the
interrelation between kinematic properties (e.g. velocity dispersions and
asymmetric drift), spatial parameters (scale-lengths and vertical density
profiles), and properties of stellar sub-populations (age and abundance
distributions). Any consistent radial extension of the disc evolution model
should predict specific features in the different distribution functions and in
their correlations. Large spectroscopic surveys (SEGUE, RAVE, APOGEE, Gaia-ESO)
allow significant constraints on the long-term evolution of the thin disc. We
discuss the qualitative difference of correlations (like the alpha-enhancement
as function of metallicity) and distribution functions (e.g. in [Mg/H] or
[Fe/H]) for the construction of a disc model. In the framework of the JJ-model
we build a local chemical enrichment model and show that significant vertical
gradients for main sequence and red clump stars are expected in the thin disc.
A Jeans analysis of the asymmetric drift provides a link to the radial
structure of the disc. The derived metallicity-dependent radial scale-lengths
can be combined in the future with the abundance distributions at different
Galactocentric distances to construct full disc models. We expect to be able to
constrain possible scenarios of inside-out growth of the thin disc and to
characterise those populations, which require significant radial migration.Comment: 5 pages, 6 figures, to appear in Astronomische Nachrichten, special
  issue "Reconstruction the Milky Way's History: Spectroscopic surveys,
  Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
  Montalb\'an, and M. Steffen, AN 2016 (in press
Lessons learnt from the Solar neighbourhood and the Kepler field

Setting the timeline of the events which shaped the Milky Way disc through
its 13 billion year old history is one of the major challenges in the theory of
galaxy formation. Achieving this goal is possible using late-type stars, which
in virtue of their long lifetimes can be regarded as fossil remnants from
various epochs of the formation of the Galaxy. There are two main paths to
reliably age-date late-type stars: astrometric distances for stars in the
turn-off and subgiant region, or oscillation frequencies along the red giant
branch. So far, these methods have been applied to large samples of stars in
the solar neighbourhood, and in the Kepler field. I review these studies,
emphasize how they complement each other, and highlight some of the constraints
they provide for Galactic modelling. I conclude with the prospects and
synergies that astrometric (Gaia) and asteroseismic space-borne missions
reserve to the field of Galactic Archaeology, and advocate that survey
selection functions should be kept as simple as possible, relying on basic
observables such as colours and magnitudes only.Comment: Invited. To appear in Astronomische Nachrichten, special issue
  "Reconstruction the Milky Way's History: Spectroscopic surveys,
  Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
  Montalb\'an, and M. Steffen, AN 2016 (in press)
Chemodynamics of the Milky Way and disc formation history: insight from
  the RAVE and Gaia-ESO surveys

Multi-object spectrographs have opened a new window on the analyses of the
chemo-dynamical properties of old Milky Way stars. These analyses allow us to
trace back the internal mechanisms and the external factors that have
influenced the evolution of our Galaxy, and therefore understand fundamental
aspects of galaxy evolution in general. Here, we present recent results from
the RAdial Velocity Experiment (RAVE) and the Gaia-ESO survey. These surveys
explore the Milky Way properties in different ways, in terms of sample size and
selection, magnitude range, and spectral resolution. We focus here on (i) the
first direct detection of evidence for radial migration within the thin disc,
providing insight into the history of spiral structure of the Milky Way, and
(ii) the chemo-dynamical characterisation of the metal-weak thick and thin
discs, for which chemo-dynamical models still have difficulties in reproducing.Comment: 5 pages, to appear in Astronomische Nachrichten, special issue
  "Reconstruction the Milky Way's History: Spectroscopic surveys,
  Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
  Montalban, and M. Steffen, AN 2016 (in press)
Angular momentum, accretion and radial flows in chemodynamical models of
  spiral galaxies

Gas accretion and radial flows are key ingredients of the chemical evolution
of spiral galaxies. They are also tightly linked to each other (accretion
drives radial flows, due to angular momentum conservation) and should therefore
be modelled simultaneously. We summarise an algorithm that can be used to
consistently compute accretion profiles, radial flows and abundance gradients
under quite general conditions and we describe illustrative applications to the
Milky Way. We find that gas-phase abundance gradients strongly depend on the
angular momentum of the accreting material and, in the outer regions, they are
significantly affected by the choice of boundary conditions.Comment: 4 pages, 2 figures. Proceedings of the 592 WE-Heraeus Seminar. To
  appear in Astronomische Nachricthen, special issue "Reconstructing the Milky
  Way's history: spectroscopic surveys, asteroseismology and chemodynamical
  models", Guest Editors C. Chiappini, J. Montalban and M. Steffe
Chemical abundance gradients from open clusters in the Milky Way disk:
  results from the APOGEE survey

Metallicity gradients provide strong constraints for understanding the
chemical evolution of the Galaxy. We report on radial abundance gradients of
Fe, Ni, Ca, Si, and Mg obtained from a sample of 304 red-giant members of 29
disk open clusters, mostly concentrated at galactocentric distances between ~8
- 15 kpc, but including two open clusters in the outer disk. The observations
are from the APOGEE survey. The chemical abundances were derived automatically
by the ASPCAP pipeline and these are part of the SDSS III Data Release 12. The
gradients, obtained from least squares fits to the data, are relatively flat,
with slopes ranging from -0.026 to -0.033 dex/kpc for the alpha-elements [O/H],
[Ca/H], [Si/H] and [Mg/H] and -0.035 dex/kpc and -0.040 dex/kpc for [Fe/H] and
[Ni/H], respectively. Our results are not at odds with the possibility that
metallicity ([Fe/H]) gradients are steeper in the inner disk (R_GC ~7 - 12 kpc)
and flatter towards the outer disk. The open cluster sample studied spans a
significant range in age. When breaking the sample into age bins, there is some
indication that the younger open cluster population in our sample (log age <
8.7) has a flatter metallicity gradient when compared with the gradients
obtained from older open clusters.Comment: 4 pages, 3 figures, To appear in Astronomische Nachrichten, special
  issue "Reconstruction the Milky Way's History: Spectroscopic surveys,
  Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
  Montalb\'an, and M. Steffen, AN 2016 (in press)
The CoRoT-GES Collaboration. Improving Red Giants spectroscopic surface
  gravity and abundances with asteroseismology

Nowadays large spectroscopic surveys, like the Gaia-ESO Survey (GES), provide
unique stellar databases for better investigating the formation and evolution
of our Galaxy. Great attention must be paid to the accuracy of the basic
stellar properties derived: large uncertainties in stellar parameters lead to
large uncertainties in abundances, distances and ages. Asteroseismology has a
key role in this context: when seismic information is combined with information
derived from spectroscopic analysis, highly precise constraints on distances,
masses, extinction and ages of Red Giants can be obtained. In the light of this
promising joint-action, we started the CoRoT-GES collaboration. We present a
set of 1,111 CoRoT stars, observed by GES from December 2011 to July 2014,
these stars belong to the CoRoT field LRc01, pointing at the inner Galactic
Disk. Among these stars, 534 have reliable global seismic parameters. By
combining seismic informations and spectroscopy, we derived precise stellar
parameters, ages, kinematic and orbital parameters and detailed element
abundances for this sample of stars. We also show that, thanks to
asteroseismology, we are able to obtain a higher precision than what can be
achieved by the standard spectroscopic means. This sample of CoRoT Red Giants,
spanning Galactocentric distances from 5 to 8 kpc and a wide age interval (1-13
Gyrs), provides us a representative sample for the inner disk population.Comment: 6 pages, 4 figures, to appear in Astronomische Nachrichten, special
  issue "Reconstruction the Milky Way's History: Spectroscopic surveys,
  Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
  Montalban, and M. Steffen, AN 2016 (in press
Galactic Archaeology with CoRoT and APOGEE: Creating mock observations
  from a chemodynamical model

In a companion paper, we have presented the combined
asteroseismic-spectroscopic dataset obtained from CoRoT lightcurves and APOGEE
infra-red spectra for 678 solar-like oscillating red giants in two fields of
the Galactic disc (CoRoGEE). We have measured chemical abundance patterns,
distances, and ages of these field stars which are spread over a large radial
range of the Milky Way's disc. Here we show how to simulate this dataset using
a chemodynamical Galaxy model. We also demonstrate how the observation
procedure influences the accuracy of our estimated ages.Comment: 5 pages, 6 figures. To appear in Astronomische Nachrichten, special
  issue "Reconstruction the Milky Way's History: Spectroscopic surveys,
  Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
  Montalb\'an, and M. Steffe
Carbon-enhanced metal-poor stars in different environments

The origin of carbon-enhanced metal-poor (CEMP) stars and their possible
connections with the chemical elements produced by the first stellar
generations is still highly debated. We briefly review observations of CEMP
stars in different environments (Galactic stellar halo, ultra-faint and
classical dwarf galaxies) and interpret their properties using cosmological
chemical-evolution models for the formation of the Local Group. We discuss the
implications of current observations for the properties of the first stars,
clarify why the fraction of carbon-enhanced to carbon-normal stars varies in
dwarf galaxies with different luminosity, and discuss the origin of the first
CEMP(-no) star found in the Sculptor dwarf galaxy.Comment: 4 pages, 4 figures. To appear in Astronomische Nachrichten, special
  issue "Reconstructing the Milky Way's History: Spectroscopic Surveys,
  Asteroseismology and Chemodynamical Models", Guest Editors C. Chiappini, J.
  Montalban, and M. Steffen, AN 2016 (in press
Milky Way chemo-dynamics in the era of Gaia

The main goal of Galactic Archaeology is understanding the formation and
evolution of the basic Galactic components. This requires sophisticated
chemo-dynamical modeling, where disc asymmetries (e.g., perturbations from the
central bar, spirals arms, and infalling satellites) and non-equilibrium
processes are taken into account self-consistently. Here we discuss the current
status of Galactic chemo-dynamical modeling and focus on a recent hybrid
technique, which helps circumvent traditional problems with chemical enrichment
and star formation encountered in fully self-consistent cosmological
simulations. We show that this model can account for a number of
chemo-kinematic relations in the Milky Way. In addition, we demonstrate that
(1) our model matches well the observed age-[alpha/Fe] and age-[Fe/H] relations
and (2) that the scatter in the age-[Fe/H] relation cannot be simply explained
by blurring (stars on apo- and pericenters visiting the solar vicinity) but
significant radial migration (stars born elsewhere but ending up at the solar
vicinity today because of a change in guiding radius) is needed. We emphasize
the importance of accurate stellar ages, such as those obtained through
asteroseismology by the CoRoT and Kepler missions, for breaking the degeneracy
among different Galactic evolution scenarios.Comment: Interesting new Fig.2. To appear in Astronomische Nachrichten,
  special issue "Reconstruction the Milky Way's History: Spectroscopic surveys,
  Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
  Montalb\'an, and M. Steffen, AN 2016 (in press)
Radial migration in numerical simulations of Milky Way-sized galaxies

We show that in N-body simulations of isolated spiral discs, spiral arms
appear to transient, recurring features that co-rotate with the stellar disc
stars at all radii. As a consequence, stars around the spiral arm continually
feel a tangential force from the spiral and gain/lose angular momentum at all
radii where spiral structure exists, without gaining significant amounts of
random energy. We demonstrate that the ubiquitous radial migration in these
simulations can be seen as outward (inward) systematic streaming motions along
the trailing (leading) side of the spiral arms. We characterise these spiral
induced peculiar motions and compare with those of the Milky Way obtained from
APOGEE red clump data. We find that transient, co-rotating spiral arms are
consistent with the data, in contrast with density wave-like spirals which are
qualitatively inconsistent. In addition, we show that, in our simulations,
radial migration does not change the radial metallicity gradient significantly,
and broadens the metallicity distribution function at all radii.Comment: 4 pages, 3 figures. To appear in Astronomische Nachrichten, special
  issue "Reconstructing the Milky Way's History: Spectroscopic surveys,
  Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
  Montalb\'an, and M. Steffen, AN 2016 (in press)
Milky Way's Thick and Thin disk: Is there distinct thick disk?

This article is based on our discussion session on Milky Way models at the
592 WE-Heraeus Seminar, Reconstructing the Milky Way's History: Spectroscopic
Surveys, Asteroseismology and Chemodynamical models. The discussion focused on
the following question: "Are there distinct thick and thin disks?". The answer
to this question depends on the definition one adopts for thin and thick disks.
The participants of this discussion converged to the idea that there are at
least two different types of disks in the Milky Way. However, there are still
important open questions on how to best define these two types of disks
(chemically, kinematically, geometrically or by age?). The question of what is
the origin of the distinct disks remains open. The future Galactic surveys
which are highlighted in this conference should help us answering these
questions. The almost one-hour debate involving researchers in the field
representing different modelling approaches (Galactic models such as TRILEGAL,
Besancon and Galaxia, chemical evolution models, extended distribution
functions method, chemodynamics in the cosmological context, and
self-consistent cosmological simulations) illustrated how important is to have
all these parallel approaches. All approaches have their advantages and
shortcomings (also discussed), and different approaches are useful to address
specific points that might help us answering the more general question above.Comment: 7 pages, no figure. To appear in Astronomische Nachrichten, special
  issue "Reconstruction the Milky Way's History: Spectroscopic surveys,
  Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
  Montalban, and M. Steffe
Kinematical properties of coronal mass ejections

Coronal mass ejections (CMEs) are the most dynamic phenomena in our solar
system. They abruptly disrupt the continuous outflow of solar wind by expelling
huge clouds of magnetized plasma into interplanetary space with velocities
enabling to cross the Sun-Earth distance within a few days. Earth-directed CMEs
may cause severe geomagnetic storms when their embedded magnetic fields and the
shocks ahead compress and reconnect with the Earth's magnetic field. The
transit times and impacts in detail depend on the initial CME velocity, size,
and mass, as well as on the conditions and coupling processes with the ambient
solar wind flow in interplanetary space. The observed CME parameters may be
severly affected by projection effects and the constant changing environmental
conditions are hard to derive. This makes it difficult to fully understand the
physics behind CME evolution, preventing to do a reliable forecast of
Earth-directed events. This short review focusing on observational data, shows
recent methods which were developed to derive the CME kinematical profile for
the entire Sun-Earth distance range as well as studies which were performed to
shed light on the physical processes that CMEs encounter when propagating from
Sun to Earth.Comment: accepted for publication in Astronomische Nachrichte
Hybrid simulations of chromospheric HXR flare sources

Recent measurements of vertical extents and positions of the chromospheric
hard X-ray (HXR) flare sources based on Ramaty High-Energy Spectroscopic Imager
(RHESSI) observations show a significant inconsistency with the theoretical
predictions based on the standard collisional thick target model (CTTM). Using
a hybrid flare code Flarix, we model simultaneously and self-consistently the
propagation, scattering and energy losses of electron beams with power-law
energy spectra and various initial pitch-angle distributions in a purely
collisional approximation and concurrently the dynamic response of the heated
chromosphere on timescales typical for RHESSI image reconstruction. The results
of the simulations are used to model the time evolution of the vertical
distribution of chromospheric HXR source within a singular (compact) loop.
Adopting the typical RHESSI imaging times scales, energy dependent vertical
sizes and positions as could be observed by RHESSI are presented.Comment: 5 pages, 4 images, accepted to Astron. Nach
Observations of solar X-ray and EUV jets and their related phenomena

Solar jets are fast-moving, elongated brightenings related to ejections seen
in both images and spectra on all scales from barely visible chromospheric jets
to coronal jets extending up to a few solar radii. The largest, most powerful
jets are the source of type III radio bursts, energetic electrons and ions with
greatly enhanced $^3$He and heavy element abundances. The frequent coronal jets
from polar and equatorial coronal holes may contribute to the solar wind. The
primary acceleration mechanism for all jets is believed to be release of
magnetic stress via reconnection; however the energy buildup depends on the
jets' source environment. In this review, we discuss how certain features of
X-ray and EUV jets, such as their repetition rate and association with radio
emission, depends on their underlying photospheric field configurations (active
regions, polar and equatorial coronal holes, and quiet Sun).Comment: (9 Pages, 8 Figures, Presented at 12th Potsdam Thinkshop "The Dynamic
  Sun - Exploring the Many Facets of Solar Eruptive Events". To be published in
  Astronomische Nachrichte
Magnetic field reconstruction based on sunspot oscillations

The magnetic field of a sunspot guides magnetohydrodynamic waves toward
higher atmospheric layers. In the upper photosphere and lower chromosphere,
wave modes with periods longer than the acoustic cut-off period become
evanescent. The cut-off period essentially changes due to the atmospheric
properties, e.g., increases for larger zenith inclinations of the magnetic
field. In this work, we aim at introducing a novel technique of reconstructing
the magnetic field inclination on the basis of the dominating wave periods in
the sunspot chromosphere and upper photosphere. On 2013 August 21st, we
observed an isolated, circular sunspot (NOAA11823) for 58 min in a purely
spectroscopic multi-wavelength mode with the Interferometric Bidimensional
Spectro-polarimeter (IBIS) at the Dunn Solar Telescope. By means of a wavelet
power analysis, we retrieved the dominating wave periods and reconstructed the
zenith inclinations in the chromosphere and upper photosphere. The results are
in good agreement with the lower photospheric HMI magnetograms. The sunspot's
magnetic field in the chromosphere inclines from almost vertical (0$^{\circ}$)
in the umbra to around 60$^{\circ}$ in the outer penumbra. With increasing
altitude in the sunspot atmosphere, the magnetic field of the penumbra becomes
less inclined. We conclude that the reconstruction of the magnetic field
topology on the basis of sunspot oscillations yields consistent and conclusive
results. The technique opens up a new possibility to infer the magnetic field
inclination in the solar chromosphere.Comment: 5 pages, 4 figures, Issue in Astron. Nachrichten on the 12th Potsdam
  Thinkshop 201
Spectropolarimetric observations of an arch filament system with the
  GREGOR solar telescope

Arch filament systems occur in active sunspot groups, where a fibril
structure connects areas of opposite magnetic polarity, in contrast to active
region filaments that follow the polarity inversion line. We used the GREGOR
Infrared Spectrograph (GRIS) to obtain the full Stokes vector in the spectral
lines Si I 1082.7 nm, He I 1083.0 nm, and Ca I 1083.9 nm. We focus on the
near-infrared calcium line to investigate the photospheric magnetic field and
velocities, and use the line core intensities and velocities of the helium line
to study the chromospheric plasma. The individual fibrils of the arch filament
system connect the sunspot with patches of magnetic polarity opposite to that
of the spot. These patches do not necessarily coincide with pores, where the
magnetic field is strongest. Instead, areas are preferred not far from the
polarity inversion line. These areas exhibit photospheric downflows of moderate
velocity, but significantly higher downflows of up to 30 km/s in the
chromospheric helium line. Our findings can be explained with new emerging flux
where the matter flows downward along the fieldlines of rising flux tubes, in
agreement with earlier results.Comment: Proceedings 12th Potsdam Thinkshop to appear in Astronomische
  Nachrichte
Solar Physics at the Einstein Tower

The solar observatory Einstein Tower (Einsteinturm) at the Telegrafenberg in
Potsdam is both a landmark of modern architecture and an important place for
solar physics. Originally built for high-resolution spectroscopy and measuring
the gravitational redshift, research shifted over the years to understanding
the active Sun and its magnetic field. Nowadays, telescope and spectrographs
are used for research and development, i.e., testing instruments and in
particular polarization optics for advanced instrumentation deployed at major
European and international astronomical and solar telescopes. In addition, the
Einstein Tower is used for educating and training of the next generation
astrophysicists as well as for education and public outreach activities
directed at the general public. This article comments on the observatory's
unique architecture and the challenges of maintaining and conserving the
building. It describes in detail the characteristics of telescope,
spectrographs, and imagers; it portrays some of the research and development
activities.Comment: 9 pages, 13 figures, accepted for publication in Astronomische
  Nachrichte