scholarly journals The Pristine Inner Galaxy Survey (PIGS) II: Uncovering the most metal-poor populations in the inner Milky Way

2020 ◽  
Vol 496 (4) ◽  
pp. 4964-4978 ◽  
Author(s):  
Anke Arentsen ◽  
Else Starkenburg ◽  
Nicolas F Martin ◽  
David S Aguado ◽  
Daniel B Zucker ◽  
...  
Keyword(s):  
Milky Way ◽  
Dynamical Evolution ◽  
Spectral Library ◽  
Data Set ◽  
Unique Data ◽  
Horizontal Branch Stars ◽  
History Of ◽  
Low Metallicity

ABSTRACT Metal-poor stars are important tools for tracing the early history of the Milky Way, and for learning about the first generations of stars. Simulations suggest that the oldest metal-poor stars are to be found in the inner Galaxy. Typical bulge surveys, however, lack low metallicity ($\rm {[Fe/H]} \lt -1.0$) stars because the inner Galaxy is predominantly metal-rich. The aim of the Pristine Inner Galaxy Survey (PIGS) is to study the metal-poor and very metal-poor (VMP, $\rm {[Fe/H]} \lt -2.0$) stars in this region. In PIGS, metal-poor targets for spectroscopic follow-up are selected from metallicity-sensitive CaHK photometry from the CFHT. This work presents the ∼250 deg2 photometric survey as well as intermediate-resolution spectroscopic follow-up observations for ∼8000 stars using AAOmega on the AAT. The spectra are analysed using two independent tools: ULySS with an empirical spectral library, and FERRE with a library of synthetic spectra. The comparison between the two methods enables a robust determination of the stellar parameters and their uncertainties. We present a sample of 1300 VMP stars – the largest sample of VMP stars in the inner Galaxy to date. Additionally, our spectroscopic data set includes ∼1700 horizontal branch stars, which are useful metal-poor standard candles. We furthermore show that PIGS photometry selects VMP stars with unprecedented efficiency: 86 per cent/80 per cent (lower/higher extinction) of the best candidates satisfy $\rm {[Fe/H]} \lt -2.0$, as do 80 per cent/63 per cent of a larger, less strictly selected sample. We discuss future applications of this unique data set that will further our understanding of the chemical and dynamical evolution of the innermost regions of our Galaxy.

Effectiveness of a Modified Version of Airflow Therapy

1982 ◽  
Vol 47 (2) ◽  
pp. 160-164
Author(s):  
Glenn L. Falkowski ◽  
Arthur M. Guilford ◽  
Jack Sandler
Keyword(s):  
Success Rate ◽  
Scientific Literature ◽  
Future Research ◽  
Relative Importance ◽  
Differential Effectiveness ◽  
History Of ◽  
One Year ◽  
Main Components

Utilizing airflow therapy, Schwartz (1976) has claimed an 89% success rate with stutterers following treatment and an 83% success rate at one year follow-up. Such claims have yet to be documented in the scientific literature. The purposes of this study were: (a) to investigate the effectiveness of a modified version of airflow therapy; (b) to examine the relative importance of its two main components—passive airflow and elongation of the first vowel spoken. The speech of two adult male stutterers with a lengthy history of stuttering, was assessed with spontaneous speaking and reading tasks. Results indicated marked improvement in both subjects' speech on the reading task was maintained at follow-up 10 weeks later. For spontaneous speech, results were generally weaker and less durable. Effects of the two treatment components were cumulative and did not allow determination of any differential effectiveness between components. Implications of these findings were considered and directions for future research discussed.

scholarly journals The Hubble PanCET program: Transit and Eclipse Spectroscopy of the Hot-Jupiter WASP-74b

2021 ◽  
Vol 162 (6) ◽  
pp. 271
Author(s):  
Guangwei Fu ◽  
Drake Deming ◽  
Erin May ◽  
Kevin Stevenson ◽  
David K. Sing ◽  
...  
Keyword(s):  
Rayleigh Scattering ◽  
Hubble Space Telescope ◽  
Absorption Feature ◽  
Spectral Library ◽  
Data Set ◽  
Space Telescope ◽  
Methane Absorption ◽  
James Webb Space Telescope ◽  
Hot Jupiter

Abstract Planets are like children with each one being unique and special. A better understanding of their collective properties requires a deeper understanding of each planet. Here we add the transit and eclipse spectra of hot-Jupiter WASP-74b into the ever growing data set of exoplanet atmosphere spectral library. With six transits and three eclipses using the Hubble Space Telescope and Spitzer Space Telescope (Spitzer), we present the most complete and precise atmospheric spectra of WASP-74b. We found no evidence for TiO/VO nor super-Rayleigh scattering reported in previous studies. The transit shows a muted water feature with strong Rayleigh scattering extending into the infrared. The eclipse shows a featureless blackbody-like WFC3/G141 spectrum and a weak methane absorption feature in the Spitzer 3.6 μm band. Future James Webb Space Telescope follow-up observations are needed to confirm these results.

scholarly journals Alterations of Left Ventricular Hypertrophy in and Survival of Patients Receiving Hemodialysis: Follow-up of an Interventional Study

2001 ◽  
Vol 12 (12) ◽  
pp. 2759-2767 ◽  
Author(s):  
Gérard M. London ◽  
Bruno Pannier ◽  
Alain P. Guerin ◽  
Jacques Blacher ◽  
Sylvain J. Marchais ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Left Ventricular ◽  
Independent Effect ◽  
Lv Mass ◽  
History Of ◽  
Cv Disease ◽  
Stage Renal Disease ◽  
End Stage

ABSTRACT. Left ventricular (LV) hypertrophy (LVH) is a risk factor for mortality in patients with end-stage renal disease (ESRD). Whether the attenuation of LVH has a positive effect on survival of patients with ESRD has not been documented. The aim of this study was to determine the effect of parallel treatment of hypertension and anemia on LV mass (LVM) and to determine the effect of LVM changes on survival. A cohort of 153 patients receiving hemodialysis was studied. The duration of follow-up was 54 ± 37 mo. All patients had echocardiographic determination of LV dimensions and LVM at baseline and regular intervals until the end of the follow-up period. During the study, BP decreased from (mean ± SD) 169.4 ± 29.7/90.2 ± 15.6 to 146.7 ± 29/78 ± 14.1 mmHg (P< 0.001), and hemoglobin increased from 8.65 ± 1.65 to 10.5 ± 1.45 g/dl (P< 0.001). The LV end-diastolic diameter and mean wall thickness decreased from 56.6 ± 6.5 to 54.8 ± 6.5 mm (P< 0.001), and from 10.4 ± 1.6 to 10.2 ± 1.6 mm (P< 0.05), respectively. The LVM decreased from 290 ± 80 to 264 ± 86 g (P< 0.01). Fifty-eight deaths occurred, 38 attributed to cardiovascular (CV) disease and 20 attributed to non-CV causes. According to Cox analyses after adjustment for age, gender, diabetes, history of CV disease, and all nonspecific CV risk factors, LVM regression positively affected the survival. The hazard risk ratio associated with a 10% LVM decrease was 0.78 (95% confidence interval, 0.63 to 0.92) for all-causes mortality and 0.72 (95% confidence interval, 0.51 to 0.90) for mortality due to CV disease. These results show that a partial LVH regression in patients with ESRD had a favorable and independent effect on patients’ all-cause and CV survival.

scholarly journals Tests of two optimal incentive models for executive stock options

2011 ◽  
Vol 9 (1) ◽  
pp. 136-155
Author(s):  
Jean M. Canil ◽  
Bruce A. Rosser
Keyword(s):  
Executive Compensation ◽  
Stock Options ◽  
Abnormal Returns ◽  
Outside Directors ◽  
Data Set ◽  
Stock Volatility ◽  
Unique Data ◽  
Exercise Price ◽  
Grant Size

Using a unique data set, we test theoretical propositions relating to grant size and exercise price in determination of optimal executive compensation. For Hall and Murphy, pay-performance sensitivity does not behave as predicted with respect to CEO risk aversion and diversification, but the latter supports observed grant size while ATM grants exhibit positive abnormal returns as predicted. Consistent with Choe, exercise price is found inversely related to leverage. The unexpected positive relation between grant size and stock volatility is conjectured driven by CEOs’ influencing large grants, which are found associated with weak corporate governance but ameliorated by outside directors.

scholarly journals A multi-decadal history of biomass burning plume heights identified using aerosol index measurements

2010 ◽  
Vol 10 (14) ◽  
pp. 6461-6469 ◽  
Author(s):  
H. Guan ◽  
R. Esswein ◽  
J. Lopez ◽  
R. Bergstrom ◽  
A. Warnock ◽  
...  
Keyword(s):  
High Altitude ◽  
Biomass Burning ◽  
Northeast Asia ◽  
Time Interval ◽  
Ozone Monitoring Instrument ◽  
Fire Plume ◽  
Data Set ◽  
History Of ◽  
Aerosol Index

Abstract. We have quantified the relationship between Aerosol Index (AI) measurements and plume height for young biomass burning plumes using coincident Ozone Monitoring Instrument (OMI) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) measurements. This linear relationship allows the determination of high-altitude plumes wherever AI data are available, and it provides a data set for validating global fire plume heights in chemistry transport models. We find that all plumes detected from June 2006 to February 2009 with an AI value ≥9 are located at altitudes higher than 5 km. Older high-altitude plumes have lower AI values than young plumes at similar altitudes. We have examined available AI data from the OMI and TOMS instruments (1978–2009) and find that large AI plumes occur more frequently over North America than over Australia or Russia/Northeast Asia. According to the derived relationship, during this time interval, 181 plumes, in various stages of their evolution, reached altitudes above 8 km.

scholarly journals The Correlation Between Kinematical Properties and Ages of Stellar Populations

1974 ◽  
Vol 3 ◽  
pp. 419-421
Author(s):  
J. Einasto
Keyword(s):  
Dynamical Evolution ◽  
Stellar Populations ◽  
Quantitative Information ◽  
Interstellar Gas ◽  
The Galaxy ◽  
History Of ◽  
Observational Errors ◽  
Time Changes ◽  
Velocity Selection

The spatial and kinematical properties of galactic populations are very conservative for time changes. Therefore the study of these properties gives us certain information on the past dynamical evolution of the Galaxy, in particular on the evolution of star generating medium (interstellar gas, as generally accepted). The detailed study of spatial structure of stellar populations in our Galaxy is possible in exceptional cases only. But the study of kinematical properties is possible practically for all populations, which makes these studies very useful for cosmogonic purpose.In order to obtain adequate quantitative information for the study of dynamical history of the Galaxy the statistical data on stellar velocities are to satisfy the following requirements: populations under study must be physically homogeneous; statistical samples of stars must be free from selection effects, especially from velocity selection; information on r.m.s. errors of observed quantities must be known in order to correct the results for accidental observational errors; the data for the determination of the age of the sample must be available.

scholarly journals Distances and ages of globular clusters

2007 ◽  
Vol 3 (S248) ◽  
pp. 440-442 ◽  
Author(s):  
B. Chaboyer
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Formation History ◽  
Minimum Age ◽  
History Of ◽  
The Mean ◽  
Age Of The Universe ◽  
The Universe ◽  
Age Determinations

AbstractAs the oldest objects whose ages can be accurately determined, Galactic globular clusters can be used to establish the minimum age of the universe (and hence, to constrain cosmological models) and to study the early formation history of the Milky Way. The largest uncertainty in the determination of globular cluster ages is the distance scale. The current uncertainty in the distances to globular clusters is ~ 6%, which leads to a 13% uncertainty in the absolute ages of globular clusters. I am the PI on a SIM-Planetquest key project to determine the distances of 21 globular clusters with an accuracy of ranging from 1 to 4%. This will lead to age determinations accurate to 5 − 9%. The mean age of the oldest, most metal-poor globular clusters will be determined with an accuracy of ±3%.

scholarly journals Surveys for Metal-Poor Stars in the Galaxy: A New Window on the Low-Abundance Universe

1998 ◽  
Vol 11 (1) ◽  
pp. 58-61
Author(s):  
T.C. Beers
Keyword(s):  
Milky Way ◽  
High Signal ◽  
Signal To Noise ◽  
Milky Way Galaxy ◽  
The Galaxy ◽  
History Of ◽  
Chemical History ◽  
Low Metallicity ◽  
New Generation ◽  
The Universe

Measurement of the abundances of the light and heavy elements in stars of the Milky Way galaxy is the cornerstone for the study of numerous aspects of chemical evolution in galaxies and the Universe. We stand poised to enter an era of rapid understanding, as new-generation telescopes with apertures in the 8m-10m class enable astronomers to obtain high-resolution, high-signal-to-noise near-UV, optical, and IR spectra of the stars which have locked up the chemical history of our Galaxy in their outer atmospheres. It is thus appropriate to review present surveys for the low-metallicity stars of our Galaxy, as the stars we uncover today will be studied so intensively in the coming decades.

scholarly journals SDSS-IV MaNGA: the ‘G-dwarf problem’ revisited

2021 ◽  
Vol 502 (1) ◽  
pp. L95-L98
Author(s):  
Michael J Greener ◽  
Michael Merrifield ◽  
Alfonso Aragón-Salamanca ◽  
Thomas Peterken ◽  
Brett Andrews ◽  
...  
Keyword(s):  
Milky Way ◽  
High Mass ◽  
Dwarf Stars ◽  
The Galaxy ◽  
Star Formation In Galaxies ◽  
History Of ◽  
Low Metallicity ◽  
Low Mass ◽  
Gas Accretion ◽  
Made In

ABSTRACT The levels of heavy elements in stars are the product of enhancement by previous stellar generations, and the distribution of this metallicity among the population contains clues to the process by which a galaxy formed. Most famously, the ‘G-dwarf problem’ highlighted the small number of low-metallicity G-dwarf stars in the Milky Way, which is inconsistent with the simplest picture of a galaxy formed from a ‘closed box’ of gas. It can be resolved by treating the Galaxy as an open system that accretes gas throughout its life. This observation has classically only been made in the Milky Way, but the availability of high-quality spectral data from SDSS-IV MaNGA and the development of new analysis techniques mean that we can now make equivalent measurements for a large sample of spiral galaxies. Our analysis shows that high-mass spirals generically show a similar deficit of low-metallicity stars, implying that the Milky Way’s history of gas accretion is common. By contrast, low-mass spirals show little sign of a G-dwarf problem, presenting the metallicity distribution that would be expected if such systems evolved as pretty much closed boxes. This distinction can be understood from the differing timescales for star formation in galaxies of differing masses.

scholarly journals A multi-decadal history of biomass burning plume heights identified using aerosol index measurements

2010 ◽  
Vol 10 (1) ◽  
pp. 1-25 ◽  
Author(s):  
H. Guan ◽  
R. Esswein ◽  
J. Lopez ◽  
R. Bergstrom ◽  
A. Warnock ◽  
...  
Keyword(s):  
High Altitude ◽  
Biomass Burning ◽  
Northeast Asia ◽  
Time Interval ◽  
Fire Plume ◽  
Data Set ◽  
History Of ◽  
The Relationship ◽  
Aerosol Index

Abstract. We have quantified the relationship between Aerosol Index (AI) measurements and plume height for young biomass burning plumes using coincident OMI and CALIPSO measurements. This linear relationship allows the determination of high-altitude plumes wherever AI data are available, and it provides a data set for validating global fire plume injection heights in chemistry transport models. We find that all plumes detected from June 2006 to February 2009 with an AI value ≥9 are located at altitudes higher than 5 km. Older high-altitude plumes have lower AI values than young plumes at similar altitudes. We have examined available AI data from the OMI and TOMS instruments (1978–2009) and find that large AI plumes occur more frequently over North America than over Australia or Russia/Northeast Asia. According to the derived relationship, during this time interval, 181 plumes reached altitudes above 8 km. One hundred and thirty-two had injection heights ≥8 km but below 12 km, and 49 were lofted to 12 km or higher, including 14 plumes injected above 16 km.

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