scholarly journals White dwarfs in the Gaia era

2017 ◽  
Vol 12 (S330) ◽  
pp. 317-320
Author(s):  
P.-E. Tremblay ◽  
N. Gentile-Fusillo ◽  
J. Cummings ◽  
S. Jordan ◽  
B. T. Gänsicke ◽  
...  
Keyword(s):  
White Dwarfs ◽  
Main Sequence ◽  
Milky Way ◽  
Mass Function ◽  
Initial Mass Function ◽  
Sequence Evolution ◽  
Atmospheric Parameters ◽  
Stellar Formation ◽  
Formation History ◽  
Data Release

AbstractThe vast majority of stars will become white dwarfs at the end of the stellar life cycle. These remnants are precise cosmic clocks owing to their well constrained cooling rates. Gaia Data Release 2 is expected to discover hundreds of thousands of white dwarfs, which can then be observed spectroscopically with WEAVE and 4MOST. By employing spectroscopically derived atmospheric parameters combined with Gaia parallaxes, white dwarfs can constrain the stellar formation history in the early developing phases of the Milky Way, the initial mass function in the 1.5 to 8 M⊙ range, and the stellar mass loss as well as the state of planetary systems during the post main-sequence evolution.

scholarly journals Evidence of spectral evolution on the white dwarf sample from the Gaia mission

2020 ◽  
Vol 492 (4) ◽  
pp. 5003-5010 ◽  
Author(s):  
G Ourique ◽  
S O Kepler ◽  
A D Romero ◽  
T S Klippel ◽  
D Koester
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Initial Mass ◽  
Spectral Evolution ◽  
Formation History ◽  
Magnitude Diagram ◽  
Double Population

ABSTRACT Since the Gaia data release 2, several works have been published describing a bifurcation in the observed white dwarf colour−magnitude diagram for ${G_{\mathrm{BP}}}{}-{G_{\mathrm{RP}}}{} \gt 0$. Some possible explanations in the literature include the existence of a double population with different initial mass functions or two distinct populations, one formed by hydrogen-envelope and one formed by helium-envelope white dwarfs. We propose instead spectral evolution to explain the bifurcation. From a population synthesis approach, we find that spectral evolution occurs for effective temperatures below ${\simeq }11\, 000\, \mathrm{K}$ and masses mainly between $0.64\, \mathrm{M}_\odot$ and $0.74\, \mathrm{M}_\odot$, which correspond to around 16 per cent of all DA white dwarfs. We also find that the Gaia white dwarf colour–magnitude diagram indicates a star formation history that decreases abruptly for objects younger than $1.4\, \mathrm{Gyr}$ and a top-heavy initial mass function for the white dwarf progenitors.

scholarly journals Dissecting 30 Doradus: Optical and Near Infrared Star Formation History of the starburst cluster NGC2070 from the Hubble Tarantula Treasury Project

2015 ◽  
Vol 12 (S316) ◽  
pp. 77-83
Author(s):  
Michele Cignoni ◽  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Near Infrared ◽  
Mass Function ◽  
Large Magellanic Cloud ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Formation History ◽  
History Of ◽  
30 Doradus

AbstractI will present new results on the star formation history of 30 Doradus in the Large Magellanic Cloud based on the panchromatic imaging survey Hubble Tarantula Treasury Project (HTTP). Here the focus is on the starburst cluster NGC2070. The star formation history is derived by comparing the deepest ever optical and NIR color-magnitude diagrams (CMDs) with state-of-the-art synthetic CMDs generated with the latest PARSEC models, which include all stellar phases from pre-main sequence to post-main sequence. For the first time in this region we are able to measure the star formation using intermediate and low mass stars simultaneously. Our results suggest that NGC2070 experienced a prolonged activity. I will discuss the detailed star formation history, initial mass function and reddening distribution.

scholarly journals Global survey of star clusters in the Milky Way

2018 ◽  
Vol 614 ◽  
pp. A22 ◽  
Author(s):  
A. E. Piskunov ◽  
A. Just ◽  
N. V. Kharchenko ◽  
P. Berczik ◽  
R.-D. Scholz ◽  
...  
Keyword(s):  
Milky Way ◽  
Cluster Formation ◽  
Formation Rate ◽  
Age Distribution ◽  
Star Clusters ◽  
Mass Function ◽  
Spatial Variations ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Formation History

Context. The all-sky Milky Way Star Clusters (MWSC) survey provides uniform and precise ages, along with other relevant parameters, for a wide variety of clusters in the extended solar neighbourhood. Aims. In this study we aim to construct the cluster age distribution, investigate its spatial variations, and discuss constraints on cluster formation scenarios of the Galactic disk during the last 5 Gyrs. Methods. Due to the spatial extent of the MWSC, we have considered spatial variations of the age distribution along galactocentric radius RG, and along Z-axis. For the analysis of the age distribution we used 2242 clusters, which all lie within roughly 2.5 kpc of the Sun. To connect the observed age distribution to the cluster formation history we built an analytical model based on simple assumptions on the cluster initial mass function and on the cluster mass-lifetime relation, fit it to the observations, and determined the parameters of the cluster formation law. Results. Comparison with the literature shows that earlier results strongly underestimated the number of evolved clusters with ages t ≳ 100 Myr. Recent studies based on all-sky catalogues agree better with our data, but still lack the oldest clusters with ages t ≳ 1 Gyr. We do not observe a strong variation in the age distribution along RG, though we find an enhanced fraction of older clusters (t > 1 Gyr) in the inner disk. In contrast, the distribution strongly varies along Z. The high altitude distribution practically does not contain clusters with t < 1 Gyr. With simple assumptions on the cluster formation history, the cluster initial mass function and the cluster lifetime we can reproduce the observations. The cluster formation rate and the cluster lifetime are strongly degenerate, which does not allow us to disentangle different formation scenarios. In all cases the cluster formation rate is strongly declining with time, and the cluster initial mass function is very shallow at the high mass end.

scholarly journals The Distribution of Planetary Nebula Nuclei in the log L-log T Plane: Inferences from Theory

1989 ◽  
Vol 131 ◽  
pp. 473-480
Author(s):  
R. A. Shaw
Keyword(s):  
Planetary Nebula ◽  
Main Sequence ◽  
Galactic Disk ◽  
Mass Function ◽  
Initial Mass Function ◽  
Sequence Evolution ◽  
Selection Effects ◽  
Core Mass ◽  
Star Forming ◽  
History Of

The expected distribution of planetary nebula nuclei (PNNs) on the log L-log T plane is calculated based upon modern stellar evolutionary theory, the initial mass function (IMF), and various assumptions concerning mass loss during post-main sequence evolution. The distribution is found to be insensitive to the assumed range of main-sequence progenitor mass, and to reasonable variations in the age and the star forming history of the galactic disk. Rather, the distribution is determined primarily by the heavy dependence of the evolution rate upon core mass, and secondarily upon the steepness of the IMF and other factors. The distribution is rather different than any found from observations, and probably reveals strong observational selection effects.

scholarly journals The population of hot subdwarf stars studied with Gaia

2020 ◽  
Vol 635 ◽  
pp. A193 ◽  
Author(s):  
S. Geier
Keyword(s):  
Proper Motion ◽  
White Dwarfs ◽  
Main Sequence ◽  
Absolute Magnitude ◽  
Radial Velocities ◽  
Horizontal Branch ◽  
Atmospheric Parameters ◽  
Main Sequence Stars ◽  
Data Release ◽  
Hot Subdwarfs

In light of substantial new discoveries of hot subdwarfs by ongoing spectroscopic surveys and the availability of new all-sky data from ground-based photometric surveys and the Gaia mission Data Release 2, we compiled an updated catalogue of the known hot subdwarf stars. The catalogue contains 5874 unique sources including 528 previously unknown hot subdwarfs and provides multi-band photometry, astrometry from Gaia, and classifications based on spectroscopy and colours. This new catalogue provides atmospheric parameters of 2187 stars and radial velocities of 2790 stars from the literature. Using colour, absolute magnitude, and reduced proper motion criteria, we identified 268 previously misclassified objects, most of which are less luminous white dwarfs or more luminous blue horizontal branch and main-sequence stars.

scholarly journals Shock Breakout of Type II Plateau Supernova

2011 ◽  
Vol 7 (S279) ◽  
pp. 413-414
Author(s):  
Nozomu Tominaga ◽  
Tomoki Morokuma ◽  
Sergei I. Blinnikov
Keyword(s):  
Theoretical Model ◽  
Main Sequence ◽  
Mass Function ◽  
Initial Mass Function ◽  
Light Curves ◽  
Star Formation History ◽  
Host Galaxy ◽  
Type Ii ◽  
Formation History ◽  
Type Ia

AbstractType II-plateau supernovae (SNe II-P) are fainter than Type Ia SNe and thus have so far been observed only at z < 1. We introduce shock breakout and propose a distant SN II-P survey at z > 1 with shock breakout. The first observation of shock breakout from the rising phase is reported in 2008. We first construct a theoretical model reproducing the UV-optical light curves (LCs) of the first example and demonstrate that the peak apparent g-band magnitude of the shock breakout would be mg ~ 26.4 mag if an identical SN occurs at a redshift z = 1, which can be reached by 8m-class telescopes. Furthermore, we present LCs of shock breakout of SN explosions with various main-sequence masses, metallicities, and explosion energies and derive the observable SN rate and reachable redshift as functions of filter and limiting magnitude by taking into account an initial mass function, cosmic star formation history, intergalactic absorption, and host galaxy extinction. The g-band observable SN rate with limiting magnitude 27.5 mag is 3.3 SNe deg−2 day−1 and half of them are located at z > 1.2.

Recovering the star formation history of galaxies through spectral fitting: Current challenges

2019 ◽  
Vol 15 (S359) ◽  
pp. 386-390
Author(s):  
Lucimara P. Martins
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Stellar Spectra ◽  
Spectral Fitting ◽  
Formation History ◽  
History Of ◽  
Nearby Galaxies ◽  
Extract Information

AbstractWith the exception of some nearby galaxies, we cannot resolve stars individually. To recover the galaxies star formation history (SFH), the challenge is to extract information from their integrated spectrum. A widely used tool is the full spectral fitting technique. This consists of combining simple stellar populations (SSPs) of different ages and metallicities to match the integrated spectrum. This technique works well for optical spectra, for metallicities near solar and chemical histories not much different from our Galaxy. For everything else there is room for improvement. With telescopes being able to explore further and further away, and beyond the optical, the improvement of this type of tool is crucial. SSPs use as ingredients isochrones, an initial mass function, and a library of stellar spectra. My focus are the stellar libraries, key ingredient for SSPs. Here I talk about the latest developments of stellar libraries, how they influence the SSPs and how to improve them.

scholarly journals The VLT-FLAMES Tarantula Survey

2016 ◽  
Vol 12 (S329) ◽  
pp. 279-286
Author(s):  
Jorick S. Vink ◽  
C.J. Evans ◽  
J. Bestenlehner ◽  
C. McEvoy ◽  
O. Ramírez-Agudelo ◽  
...  
Keyword(s):  
Mass Loss ◽  
Main Sequence ◽  
Massive Stars ◽  
Mass Function ◽  
Large Magellanic Cloud ◽  
Initial Mass Function ◽  
Data Set ◽  
Large Program ◽  
Medium Resolution ◽  
Key Questions

AbstractWe present a number of notable results from the VLT-FLAMES Tarantula Survey (VFTS), an ESO Large Program during which we obtained multi-epoch medium-resolution optical spectroscopy of a very large sample of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). This unprecedented data-set has enabled us to address some key questions regarding atmospheres and winds, as well as the evolution of (very) massive stars. Here we focus on O-type runaways, the width of the main sequence, and the mass-loss rates for (very) massive stars. We also provide indications for the presence of a top-heavy initial mass function (IMF) in 30 Dor.

scholarly journals Local disc model in view of Gaia DR1 and RAVE data

2018 ◽  
Vol 620 ◽  
pp. A71 ◽  
Author(s):  
K. Sysoliatina ◽  
A. Just ◽  
I. Koutsouridou ◽  
E. K. Grebel ◽  
G. Kordopatis ◽  
...  
Keyword(s):  
Main Sequence ◽  
Galactic Plane ◽  
Formation Rate ◽  
Velocity Distribution Function ◽  
Initial Mass Function ◽  
Selection Function ◽  
Thin Disc ◽  
Disc Model ◽  
Starting Point ◽  
Data Release

Aims. We test the performance of the semi-analytic self-consistent Just-Jahreiß disc model (JJ model) with the astrometric data from the Tycho-Gaia Astrometric Solution (TGAS) sub-catalogue of the first Gaia data release (Gaia DR1), as well as the radial velocities from the fifth data release of the Radial Velocity Experiment survey (RAVE DR5). Methods. We used a sample of 19 746 thin-disc stars from the TGAS×RAVE cross-match selected in a local solar cylinder of 300 pc radius and 1 kpc height below the Galactic plane. Based on the JJ model, we simulated this sample via the forward modelling technique. First, we converted the predicted vertical density laws of the thin-disc populations into a mock sample. For this we used the Modules and Experiments in Stellar Astrophysics (MESA) Isochrones and Stellar Tracks (MIST), a star formation rate (SFR) that decreased after a peak at 10 Gyr ago, and a three-slope broken power-law initial mass function (IMF). Then the obtained mock populations were reddened with a 3D dust map and were subjected to the selection criteria corresponding to the RAVE and TGAS observational limitations as well as to additional cuts applied to the data sample. We calculated the quantities of interest separately at different heights above the Galactic plane, taking the distance error effects in horizontal and vertical directions into account separately. Results. The simulated vertical number density profile agrees well with the data. An underestimation of the stellar numbers begins at ∼800 pc from the Galactic plane, which is expected as the possible influence of populations from |z| > 1 kpc is ignored during the modelling. The lower main sequence (LMS) is found to be thinner and under-populated by 3.6% relative to the observations. The corresponding deficits for the upper main sequence (UMS) and red giant branch (RGB) are 6% and 34.7%, respectively. However, the intrinsic uncertainty related to the choice of stellar isochrones is ∼10% in the total stellar number. The vertical velocity distribution function f(|W|) simulated for the whole cylinder agrees to within 1σ with the data. This marginal agreement arises because the dynamically cold populations at heights < 200 pc from the Galactic plane are underestimated. We also find that the model gives a fully realistic representation of the vertical gradient in stellar populations when studying the Hess diagrams for different horizontal slices. We also checked and confirm the consistency of our results with the newly available second Gaia data release (DR2). Conclusions. Based on these results and considering the uncertainties in the data selection as well as the sensitivity of the simulations to the sample selection function, we conclude that the fiducial JJ model confidently reproduces the vertical trends in the thin-disc stellar population properties. Thus, it can serve as a starting point for the future extension of the JJ model to other Galactocentric distances.

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