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

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.

2017 ◽  
Vol 13 (S334) ◽  
pp. 158-161
Author(s):  
Edouard J. Bernard

AbstractTaking advantage of the Gaia DR1, we combined TGAS parallaxes with the 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. Our dynamically-evolved SFH is in excellent agreement with that calculated from the Hipparcos catalogue within 80 pc of the Sun, showing an enhanced star formation rate (SFR) in the past ~4 Gyr. We then correct the SFR for the disc thickening with age to obtain a SFR that is representative of the whole solar cylinder, and show that even with an extreme correction our results are not consistent with an exponentially decreasing SFR as found by recent studies. Finally, we discuss how this technique can 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.


1999 ◽  
Vol 192 ◽  
pp. 151-157
Author(s):  
C. Gallart ◽  
W. L. Freedman

We advance some results of our study of the star formation history of the Local Group dSph galaxy Leo I, obtained through the analysis of its deep HST color-magnitude diagram (CMD) using model CMDs computed from stellar evolutionary models. We conclude that most star formation (≃ 90%) took place in Leo I between 7 and 1 Gyr ago. It seems to have started at a very low rate ≃ 15 Gyr ago and continued, also at a very low rate, from 1 Gyr ago until the present time. A constant Z=0.0004 and a large fraction of binary stars are required to obtain the best agreement with both the distribution of stars across the CMD and with its morphology. An IMF like the one obtained by Kroupa et al. (1993) for the solar neighborhood, or steeper, is compatible with the data.


1999 ◽  
Vol 190 ◽  
pp. 8-14
Author(s):  
F.D.A. Hartwick

We use observations and evolutionary models of local objects to interpret a recent determination of the star-formation history of the universe. By fitting the global star-formation rate, the model predicts the ratio of spheroid to disk mass of ~1, an intergalactic medium (IGM) whose mass is ~2.3 times the mass in stars, and whose metallicity is ~0.1 Z⊙.


2005 ◽  
Vol 1 (C198) ◽  
pp. 25-29 ◽  
Author(s):  
Carme Gallart ◽  
Antonio Aparicio ◽  
R. Zinn ◽  
R. Buonanno ◽  
E. Hardy ◽  
...  

2015 ◽  
Vol 814 (2) ◽  
pp. 96 ◽  
Author(s):  
Tracy M. A. Webb ◽  
Adam Muzzin ◽  
Allison Noble ◽  
Nina Bonaventura ◽  
James Geach ◽  
...  

2020 ◽  
Vol 501 (1) ◽  
pp. 302-328
Author(s):  
Jairo A Alzate ◽  
Gustavo Bruzual ◽  
Daniel J Díaz-González

ABSTRACT The Gaia data release 2 (DR2) catalogue is the best source of stellar astrometric and photometric data available today. The history of the Milky Way galaxy is written in stone in this data set. Parallaxes and photometry tell us where the stars are today, when were they formed, and with what chemical content, that is, their star formation history (SFH). We develop a Bayesian hierarchical model suited to reconstruct the SFH of a resolved stellar population. We study the stars brighter than $G\, =\, 15$ within 100 pc of the Sun in Gaia DR2 and derive an SFH of the solar neighbourhood in agreement with previous determinations and improving upon them because we detect chemical enrichment. Our results show a maximum of star formation activity about 10 Gyr ago, producing large numbers of stars with slightly below solar metallicity (Z  =  0.014), followed by a decrease in star formation up to a minimum level occurring around 8 Gyr ago. After a quiet period, star formation rises to a maximum at about 5 Gyr ago, forming stars of solar metallicity (Z  =  0.017). Finally, star formation has been decreasing until the present, forming stars of Z  =  0.03 at a residual level. We test the effects introduced in the inferred SFH by ignoring the presence of unresolved binary stars in the sample, reducing the apparent limiting magnitude, and modifying the stellar initial mass function.


2006 ◽  
Vol 2 (S235) ◽  
pp. 320-320
Author(s):  
L. Makarova ◽  
D. Makarov ◽  
A. Dolphin ◽  
I. Karachentsev ◽  
B. Tully ◽  
...  

We derive quantitative star formation histories (SFH) of the two dwarf spheroidal (KK 197 and ESO 269-066) and one dwarf irregular (ESO 381-018) galaxies in the nearby Centaurus A group. The data are part of our sample of about 50 nearby dwarf galaxies observed with the Advanced Camera for Surveys (ACS) at the Hubble Space Telescope (prog. 9771 & 10235, PI I.Karachentsev). Deep color-magnitude diagram (CMD) of KK 197 is shown in Fig.1.


2008 ◽  
Vol 4 (S255) ◽  
pp. 217-223
Author(s):  
Francesco Calura

AbstractThe long GRB 050730 observed at redshiftz~ 4 allowed the determination of the elemental abundances for a set of different chemical elements. We use detailed chemical evolution models taking into account also dust production to constrain the star formation history of the host galaxy of this long GRB. For the host galaxy of GRB 050730, we derive also some dust-related quantities and the specific star formation rate, namely the star formation rate per unit stellar mass. Finally, we compare the properties of the GRB host galaxy with those of Quasar Damped Lyman Alpha absorbers.


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