scholarly journals Dynamical ages of the young local associations with Gaia

2018 ◽  
Vol 615 ◽  
pp. A51 ◽  
Author(s):  
N. Miret-Roig ◽  
T. Antoja ◽  
M. Romero-Gómez ◽  
F. Figueras
Keyword(s):  
Star Formation ◽  
The Sun ◽  
Place Of Birth ◽  
Data Release ◽  
Error Treatment ◽  
Consistent Manner ◽  
Observational Errors ◽  
Rigorous Error ◽  
Orbital Analysis ◽  
Age Determinations

Context. The young local associations (YLAs) constitute an excellent sample for the study of a variety of astrophysical topics, especially the star formation process in low-density environments. Data from the Gaia mission allows us to undertake studies of the YLAs with unprecedented accuracy. Aims. We determine the dynamical age and place of birth of a set of associations in a uniform and dynamically consistent manner. There are nine YLAs in our sample ϵ Chamaeleontis, TW Hydrae, β Pictoris, Octans, Tucana-Horologium, Columba, Carina, Argus, and AB Doradus. Methods. We designed a method for deriving the dynamical age of the YLAs based on the orbital integration. The method involves a strategy to account for the effect of observational errors. We tested the method using mock YLAs. Finally, we applied it to our set of nine YLAs with astrometry from the first Gaia data release and complementary on-ground radial velocities from the literature. Results. Our orbital analysis yields a first estimate of the dynamical age of 33−0+9 Myr, 1313−0+7 Myr, and 55−0+23 Myr for ϵ Chamaeleontis, β Pictoris, and Tucana-Horologium, respectively. For four other associations (Octans, Columba, Carina, and Argus), we provide a lower limit for the dynamical age. Our rigorous error treatment indicates that TW Hydrae and AB Doradus deserve further study. Conclusions. The dynamical ages that we obtain are compatible spectroscopic and isochrone fitting ages obtained elsewhere. From the orbital analysis, we suggest a scenario for these YLAs where there were two episodes of star formation: one ~40 Myr ago in the first quadrant that gave birth to ϵ Chamaeleontis, TW Hydrae, and β Pictoris, and another 5−15 Myr ago close to the Sun that formed Tucana-Horologium, Columba, and Carina. Future Gaia data will provide the necessary accuracy to improve the present results, especially for the controversial age determinations, and additional evidence for the proposed scenario once a complete census of YLAs and better membership can be obtained.

scholarly journals Gaia DR1 completeness within 250 pc & star formation history of the Solar neighbourhood

2017 ◽  
Vol 12 (S330) ◽  
pp. 148-151 ◽  
Author(s):  
Edouard J. Bernard
Keyword(s):  
Star Formation ◽  
Star Formation History ◽  
Solar Neighbourhood ◽  
The Sun ◽  
Thick Disc ◽  
Formation History ◽  
Magnitude Diagram ◽  
History Of

AbstractWe took advantage of the Gaia DR1 to combine TGAS parallaxes with Tycho-2 and APASS photometry to calculate the star formation history (SFH) of the solar neighbourhood within 250 pc using the colour-magnitude diagram fitting technique. We present the determination of the completeness within this volume, and compare the resulting SFH with that calculated from the Hipparcos catalogue within 80 pc of the Sun. We also show how this technique will be applied out to ~5 kpc thanks to the next Gaia data releases, which will allow us to quantify the SFH of the thin disc, thick disc and halo in situ, rather than extrapolating based on the stars from these components that are today in the solar neighbourhood.

scholarly journals Search for stellar companions of exoplanet host stars by exploring the second ESA-Gaia data release

2019 ◽  
Vol 490 (4) ◽  
pp. 5088-5102 ◽  
Author(s):  
M Mugrauer
Keyword(s):  
Main Sequence ◽  
Stellar Systems ◽  
Sequence Evolution ◽  
The Sun ◽  
M Dwarfs ◽  
Primary Star ◽  
True Nature ◽  
Quadruple System ◽  
Data Release ◽  
Host Stars

ABSTRACT A new survey is presented, which explores the second data release of the ESA-Gaia mission, in order to search for stellar companions of exoplanet host stars, located at distances closer than about 500 pc around the Sun. In total, 176 binaries, 27 hierarchical triples, and one hierarchical quadruple system are detected among more than 1300 exoplanet host stars, whose multiplicity is investigated, yielding a multiplicity rate of the exoplanet host stars of at least about 15  per cent. The detected companions and the exoplanet host stars are equidistant and share a common proper motion, as it is expected for gravitationally bound stellar systems, proven with their accurate Gaia astrometry. The companions exhibit masses in the range between about 0.078 and 1.4 M⊙ with a peak in their mass distribution between 0.15 and $0.3\, \mathrm{M}_{\odot }$. The companions are separated from the exoplanet host stars by about 20 up to 9100 au, but are found most frequently within a projected separation of 1000 au. While most of the detected companions are early M dwarfs, eight white dwarf companions of exoplanet host stars are also identified in this survey, whose true nature is revealed with their photometric properties. Hence, these degenerated companions and the exoplanet host stars form evolved stellar systems with exoplanets, which have survived (physically but also dynamically) the post-main-sequence evolution of their former primary star.

scholarly journals Disks and Toroids Around Young Stars

1987 ◽  
Vol 115 ◽  
pp. 239-253 ◽  
Author(s):  
L.F. Rodríguez
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Observational Evidence ◽  
Young Stars ◽  
The Other ◽  
Main Sequence Star ◽  
Circumstellar Disk ◽  
The Sun ◽  
Bipolar Outflows ◽  
The One

We review the observational evidence for interstellar and circumstellar size gaseous structures that appear to be collimating the bipolar outflows observed in regions of star formation. In particular, there is growing evidence for circumstellar disk-like objects that may be related to a protoplanetary cloud like the one that once surrounded the Sun. There are similarities between these disks around young stars and that found around the main sequence star β Pictoris. Both flattened structures around L1551 IRS5 and β Pictoris appear to have an inner “hole” with radius of a few tens of AU. On the other hand, there is observational support for focusing and collimation processes acting on the same source from tens of AU (circumstellar dimensions) to tenths of pc (interstellar dimensions).

Further Investigation of the Effect of Galaxy Interactions on Star Formation

2013 ◽  
Vol 22 (2) ◽  
Author(s):  
Xin-Fa Deng ◽  
Fuyang Zhang
Keyword(s):  
Star Formation ◽  
Survey Data ◽  
Control Sample ◽  
Sloan Digital Sky Survey ◽  
Apparent Magnitude ◽  
Galaxy Interactions ◽  
Main Galaxy ◽  
Sky Survey ◽  
Data Release ◽  
Galaxy Sample

AbstractFrom the apparent magnitude-limited the Main galaxy sample of the Sloan Digital Sky Survey Data Release 7, we construct a paired galaxy sample and a control sample without close companions with the projected separations

scholarly journals Close stellar encounters with the Sun from the first Gaia Data Release

2017 ◽  
Vol 12 (S330) ◽  
pp. 144-147
Author(s):  
Coryn A. L. Bailer-Jones
Keyword(s):  
The Sun ◽  
Preliminary Results ◽  
Data Release

AbstractI present preliminary results of searching for close stellar encounters with the Sun using the first Gaia data release. Gl 710 is found to be a much closer encounter than found in pre-TGAS studies. More detailed results will be reported in an upcoming publication (Bailer-Jones 2017, in preparation).

scholarly journals Finding Ages for Old Stellar Populations

1996 ◽  
Vol 171 ◽  
pp. 71-74 ◽  
Author(s):  
Guy Worthey
Keyword(s):  
Star Formation ◽  
Elliptical Galaxy ◽  
Stellar Populations ◽  
Age Determinations

We are far from being able to populate a histogram of star formation versus time for an elliptical galaxy based solely on observations of its spectrum, but the path toward such a dream is becoming more clear. Still, we are denied the easiest paths, and most of what I have been thinking about in the last six months are the obstacles rather than the opportunities in age determinations for old stellar populations, and Es in particular. The following list should illustrate what I mean.

GRAVITATIONAL COLLAPSE AND FRAGMENTATION OF MOLECULAR CLOUD CORES

2001 ◽  
Vol 10 (02) ◽  
pp. 115-211 ◽  
Author(s):  
LEONARDO DI G. SIGALOTTI ◽  
JAIME KLAPP
Keyword(s):  
Star Formation ◽  
Binary Stars ◽  
Molecular Cloud ◽  
Main Sequence ◽  
Numerical Models ◽  
Present Theory ◽  
Main Sequence Stars ◽  
Consistent Manner ◽  
Cloud Cores ◽  
Observational Knowledge

The detected multiplicity of main-sequence and pre-main-sequence stars along with the emerging evidence for binary and multiple protostars, imply that stars may ultimately form by fragmentation of collapsing molecular cloud cores. These discoveries, coupled with recent observational knowledge of the structure of dense cloud cores and of the properties of young binary stars, provide serious constraints to the theory of star formation. Most theoretical progress in the field of star formation is largely based on numerical calculations of the early collapse and fragmentation of protostellar clouds. Although these models have been quite successful at predicting the formation of binary protostars, a direct comparison between theory and observations has not yet been established. The results of recent observations as well as of early and recent analytic and numerical models, on which the present theory of star formation is based, are reviewed here in a self-consistent manner.

scholarly journals H i-MaNGA: tracing the physics of the neutral and ionized ISM with the second data release

2021 ◽  
Vol 503 (1) ◽  
pp. 1345-1366
Author(s):  
David V Stark ◽  
Karen L Masters ◽  
Vladimir Avila-Reese ◽  
Rogemar Riffel ◽  
Rogerio Riffel ◽  
...  
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Equivalent Width ◽  
Surface Brightness ◽  
Formation Rate ◽  
Optical Emission ◽  
All Optical ◽  
Data Release ◽  
Green Bank Telescope

ABSTRACT We present the second data release for the H i-MaNGA programme of H i follow-up observations for the SDSS-IV MaNGA survey. This release contains measurements for 3669 unique galaxies, combining 2108 Green Bank Telescope observations with an updated crossmatch of the MaNGA sample with the ALFALFA survey. We combine these data with MaNGA spectroscopic measurements to examine relationships between H i-to-stellar mass ratio (${\rm M_{H\, {\small I}}/{M_*}}$) and average ISM/star formation properties probed by optical emission lines. ${\rm M_{H\, {\small I}}/{M_*}}$ is very weakly correlated with the equivalent width of H α, implying a loose connection between the instantaneous star formation rate and the H i reservoir, although the link between ${\rm M_{H\, {\small I}}/{M_*}}$ and star formation strengthens when averaged even over only moderate time-scales (∼30 Myr). Galaxies with elevated H i depletion times have enhanced [O i]/H α and depressed H α surface brightness, consistent with more H i residing in a diffuse and/or shock-heated phase that is less capable of condensing into molecular clouds. Of all optical lines, ${\rm M_{H\, {\small I}}/{M_*}}$ correlates most strongly with oxygen equivalent width, EW(O), which is likely a result of the existing correlation between ${\rm M_{H\, {\small I}}/{M_*}}$ and gas-phase metallicity. Residuals in the ${\rm M_{H\, {\small I}}/{M_*}}$−EW(O) relation are again correlated with [O i]/H α and H α surface brightness, suggesting they are also driven by variations in the fraction of diffuse and/or shock-heated gas. We recover the strong anticorrelation between ${\rm M_{H\, {\small I}}/{M_*}}$ and gas-phase metallicity seen in previous studies. We also find a relationship between ${\rm M_{H\, {\small I}}/{M_*}}$ and [O i]6302/H α, suggesting that higher fractions of diffuse and/or shock-heated gas are more prevalent in gas-rich galaxies.

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