HTLV tax and mycosis fungoides Pancake, B A; Zucker-Franklin, D
The New England journal of medicine,
1993-Aug-19, Volume:
329, Issue:
8
Journal Article
The results from the ESA Gaia astrometric mission and deep photometric surveys have revolutionized our knowledge of the Milky Way. There are many ongoing efforts to search these data for stellar ...substructure to find evidence of individual accretion events that built up the Milky Way and its halo. One of these newly identified features, called Nyx, was announced as an accreted stellar stream traveling in the plane of the disk. Using a combination of elemental abundances and stellar parameters from the GALAH and APOGEE surveys, we find that the abundances of the highest likelihood Nyx members are entirely consistent with membership of the thick disk, and inconsistent with a dwarf galaxy origin. We conclude that the postulated Nyx stream is most probably a high-velocity component of the Milky Way's thick disk. With the growing availability of large data sets including kinematics, stellar parameters, and detailed abundances, the probability of detecting chance associations increases, and hence new searches for substructure require confirmation across as many data dimensions as possible.
GALAH+ is a magnitude-limited survey of high resolution stellar spectra obtained by the HERMES spectrograph at the Australian Astronomical Observatory. Its third data release provides reduced spectra ...with new derivations of stellar parameters and abundances of 30 chemical elements for 584,015 dwarfs and giants, 88% of them in the Gaia magnitude range 11 < G < 14. Here we use these improved values of stellar parameters to build a library of observed spectra which is useful to study variations of individual spectral lines with stellar parameters. This and other improvements are used to derive radial velocities with uncertainties which are generally within 0.1 km/s or ~25% smaller than in the previous release. Median differences in radial velocities measured here and by the Gaia DR2 or APOGEE DR16 surveys are smaller than 30 m/s, a larger offset is present only for Gaia measurements of giant stars. We identify 4483 stars with intrinsically variable velocities and 225 stars for which the velocity stays constant over >=3 visits spanning more than a year. The combination of radial velocities from GALAH+ with distances and sky plane motions from Gaia enables studies of dynamics within streams and clusters. For example, we estimate that the open cluster M67 has a total mass of ~3300 Msun and its outer parts seem to be expanding, though astrometry with a larger time-span than currently available from Gaia eDR3 is needed to judge if the latter result is real.
MNRAS, 510, 2407 (2022) Since the advent of $Gaia$ astrometry, it is possible to identify massive
accreted systems within the Galaxy through their unique dynamical signatures.
One such system, ...$Gaia$-Sausage-Enceladus (GSE), appears to be an early
"building block" given its virial mass $> 10^{10}\,\mathrm{M_\odot}$ at infall
($z\sim1-3$). In order to separate the progenitor population from the
background stars, we investigate its chemical properties with up to 30 element
abundances from the GALAH+ Survey Data Release 3 (DR3). To inform our choice of
elements for purely chemically selecting accreted stars, we analyse 4164 stars
with low-$\alpha$ abundances and halo kinematics. These are most different to
the Milky Way stars for abundances of Mg, Si, Na, Al, Mn, Fe, Ni, and Cu. Based
on the significance of abundance differences and detection rates, we apply
Gaussian mixture models to various element abundance combinations. We find the
most populated and least contaminated component, which we confirm to represent
GSE, contains 1049 stars selected via Na/Fe vs. Mg/Mn in GALAH+ DR3. We
provide tables of our selections and report the chrono-chemodynamical
properties (age, chemistry, and dynamics). Through a previously reported clean
dynamical selection of GSE stars, including $30 <
\sqrt{J_R~/~\mathrm{kpc\,km\,s^{-1}}} < 55$, we can characterise an
unprecedented 24 abundances of this structure with GALAH+ DR3. Our chemical
selection allows us to prevent circular reasoning and characterise the
dynamical properties of the GSE, for example mean
$\sqrt{J_R~/~\mathrm{kpc\,km\,s^{-1}}} = 26_{-14}^{+9}$. We find only
$(29\pm1)\%$ of the GSE stars within the clean dynamical selection region. Our
methodology will improve future studies of accreted structures and their
importance for the formation of the Milky Way.
Open clusters are unique tracers of the history of our own Galaxy's disk. According to our membership analysis based on \textit{Gaia} astrometry, out of the 226 potential clusters falling in the ...footprint of GALAH or APOGEE, we find that 205 have secure members that were observed by at least one of the survey. Furthermore, members of 134 clusters have high-quality spectroscopic data that we use to determine their chemical composition. We leverage this information to study the chemical distribution throughout the Galactic disk of 21 elements, from C to Eu. The radial metallicity gradient obtained from our analysis is \(-\)0.076\(\pm\)0.009 dex kpc\(^{-1}\), which is in agreement with previous works based on smaller samples. Furthermore, the gradient in the Fe/H - guiding radius (r\(_{\rm guid}\)) plane is \(-\)0.073\(\pm\)0.008 dex kpc\(^{-1}\). We show consistently that open clusters trace the distribution of chemical elements throughout the Galactic disk differently than field stars. In particular, at given radius, open clusters show an age-metallicity relation that has less scatter than field stars. As such scatter is often interpreted as an effect of radial migration, we suggest that these differences are due to the physical selection effect imposed by our Galaxy: clusters that would have migrated significantly also had higher chances to get destroyed. Finally, our results reveal trends in the X/Fe\(-\)r$_{\rm guid}$$-$age space, which are important to understand production rates of different elements as a function of space and time.
We present high-resolution Magellan/MIKE spectroscopy of 42 red giant stars in seven stellar streams confirmed by the Southern Stellar Stream Spectroscopic Survey (S5): ATLAS, Aliqa Uma, Chenab, ...Elqui, Indus, Jhelum, and Phoenix. Abundances of 30 elements have been derived from over 10,000 individual line measurements or upper limits using photometric stellar parameters and a standard LTE analysis. This is currently the most extensive set of element abundances for stars in stellar streams. Three streams (ATLAS, Aliqa Uma, and Phoenix) are disrupted metal-poor globular clusters, although only weak evidence is seen for the light element anticorrelations commonly observed in globular clusters. Four streams (Chenab, Elqui, Indus, and Jhelum) are disrupted dwarf galaxies, and their stars display abundance signatures that suggest progenitors with stellar masses ranging from \(10^6-10^7 M_\odot\). Extensive description is provided for the analysis methods, including the derivation of a new method for including the effect of stellar parameter correlations on each star's abundance and uncertainty. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.
Globular clusters are some of the oldest bound stellar structures observed in the Universe. They are ubiquitous in large galaxies and are believed to trace intense star formation events and the ...hierarchical build-up of structure. Observations of globular clusters in the Milky Way, and a wide variety of other galaxies, have found evidence for a `metallicity floor', whereby no globular clusters are found with chemical (`metal') abundances below approximately 0.3 to 0.4 per cent of that of the Sun. The existence of this metallicity floor may reflect a minimum mass and a maximum redshift for surviving globular clusters to form, both critical components for understanding the build-up of mass in the universe. Here we report measurements from the Southern Stellar Streams Spectroscopic Survey of the spatially thin, dynamically cold Phoenix stellar stream in the halo of the Milky Way. The properties of the Phoenix stream are consistent with it being the tidally disrupted remains of a globular cluster. However, its metal abundance (Fe/H = -2.7) is substantially below that of the empirical metallicity floor. The Phoenix stream thus represents the debris of the most metal-poor globular cluster discovered so far, and its progenitor is distinct from the present-day globular cluster population in the local Universe. Its existence implies that globular clusters below the metallicity floor have probably existed, but were destroyed during Galactic evolution.
The ESA Gaia astrometric mission has enabled the remarkable discovery that a large fraction of the stars near the Solar neighbourhood appear to be debris from a single in-falling system, the ...so-called Gaia-Enceladus-Sausage (GSE). One exciting feature of this result is that it gives astronomers for the first time a large sample of easily observable unevolved stars that formed in an extra-Galactic environment, which can be compared to stars that formed within our Milky Way. Here we use these stars to investigate the "Spite Plateau" -- the near-constant lithium abundance observed in metal-poor dwarf stars across a wide range of metallicities (-3<Fe/H<-1). In particular our aim is to test whether the stars that formed in the GSE show a different Spite Plateau to other Milky Way stars that inhabit the disk and halo. Individual galaxies could have different Spite Plateaus -- e.g., the ISM could be more depleted in lithium in a lower galactic mass system due to it having a smaller reservoir of gas. We identified 76 GSE dwarf stars observed and analyzed by the GALactic Archeology with HERMES (GALAH) survey as part of its Third Data Release. Orbital actions were used to select samples of Gaia-Enceladus stars, and comparison samples of halo and disk stars. We find that the Gaia-Enceladus stars show the same lithium abundance as other likely accreted stars and in situ Milky Way stars, strongly suggesting that the "lithium problem" is not a consequence of the formation environment. This result fits within the growing consensus that the Spite Plateau, and more generally the "cosmological lithium problem" -- the observed discrepancy between the amount of lithium in warm, metal-poor dwarf stars in our Galaxy, and the amount of lithium predicted to have been produced by Big Bang Nucleosynthesis -- is the result of lithium depletion processes within stars.
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