Synergies between Massive Stars and Metal-poor Dwarf Irregular Galaxies

2018 ◽  
Vol 14 (S344) ◽  
pp. 178-181
Author(s):  
Miriam Garcia ◽  
Artemio Herrero ◽  
Francisco Najarro ◽  
Norberto Castro ◽  
Inés Camacho
Keyword(s):  
Massive Stars ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Ob Stars ◽  
Irregular Galaxies ◽  
Formation History ◽  
Population Iii Stars ◽  
Dwarf Irregular Galaxies ◽  
Cosmic History

AbstractThe community of massive stars is working intensively on Local Group dwarf irregular galaxies (dIrr). They are a reservoir of metal-poor massive stars that serve to understand the physics of their higher redshift siblings and population III stars, interpret the farthest, most energetic SNe and GRBs, and compute feedback through Cosmic History. Along the way, we became interested in the recent star-formation history and initial mass-function of the host dIrr’s, their chemical evolution, and gas and dust content. Our team is working to unveil and characterize with spectroscopy the OB-stars in IC 1613, Sextans A and SagDIG, that form a sequence of decreasing metal content. We showcase some results to stimulate synergies between both communities.

scholarly journals Comment on “An excess of massive stars in the local 30 Doradus starburst”

Science ◽  
2018 ◽  
Vol 361 (6400) ◽  
pp. eaat6506 ◽  
Author(s):  
Will M. Farr ◽  
Ilya Mandel
Keyword(s):  
Star Formation ◽  
Power Law ◽  
Ad Hoc ◽  
Massive Stars ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Formation History ◽  
Power Law Exponent ◽  
Stellar Initial Mass Function

Schneider et al. (Reports, 5 January 2018, p. 69) used an ad hoc statistical method in their calculation of the stellar initial mass function. Adopting an improved approach, we reanalyze their data and determine a power-law exponent of 2.05−0.13+0.14. Alternative assumptions regarding dataset completeness and the star formation history model can shift the inferred exponent to 2.11−0.17+0.19 and 2.15−0.13+0.13, respectively.

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 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 Winds of metal-poor OB stars: Updates from HST-COS UV spectroscopy

2014 ◽  
Vol 9 (S307) ◽  
pp. 41-46
Author(s):  
M. García ◽  
A. Herrero ◽  
F. Najarro ◽  
D. J. Lennon ◽  
M. A. Urbaneja
Keyword(s):  
Massive Stars ◽  
Uv Spectroscopy ◽  
Star Formation History ◽  
First Stars ◽  
Abundance Pattern ◽  
Ob Stars ◽  
Formation History ◽  
History Of ◽  
Strong Winds

AbstractIn the race to break the SMC frontier and reach metallicity conditions closer to the First Stars the information from UV spectroscopy is usually overlooked. New HST-COS observations of OB stars in the metal-poor galaxy IC1613, with oxygen content ~1/10 solar, have proved the important role of UV spectroscopy to characterize blue massive stars and their winds. The terminal velocities (υ∞) and abundances derived from the dataset have shed new light on the problem of metal-poor massive stars with strong winds. Furthermore, our results question the υ∞-υesc and υ∞-Z scaling relations whose use in optical-only studies may introduce large uncertainties in the derived mass loss rates and wind-momenta. Finally, our results indicate that the detailed abundance pattern of each star may have a non-negligible impact on its wind properties, and scaling these as a function of one single metallicity parameter is probably too coarse an approximation. Considering, for instance, that the [α/Fe] ratio evolves with the star formation history of each galaxy, we may be in need of updating all our wind recipes.

scholarly journals Star formation histories in dwarf irregular galaxies in the Local Group

1991 ◽  
Vol 148 ◽  
pp. 343-344
Author(s):  
L. Greggio ◽  
G. Marconi ◽  
P. Focardi ◽  
M. Tosi
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Mass Function ◽  
Initial Mass Function ◽  
Main Sequence Stars ◽  
Star Formation Activity ◽  
Irregular Galaxies ◽  
Ccd Observations ◽  
Star Formation Histories ◽  
Dwarf Irregular Galaxies

The process of star formation (SF) and the modalities with which it occurs in galaxies of different sizes are still poorly understood. On the other hand, interpretation of the chemical and photometric properties of galaxies requires the adoption of adequate laws for the SF rate and Initial Mass Function (IMF) in model computations. Dwarf irregular galaxies in the Local Group offer the chance to study their SF history through analysis of their HR diagrams, which can be derived down to V 25, corresponding to MV0, i.e. to main sequence stars of 2 M⊙. Therefore, for these galaxies, we can derive information on the star formation activity which has occurred over the last 1 Gyr approximately. In this framework, we have undertaken CCD observations of Dwarf irregular galaxies in the Local Group with ESO telescopes and briefly present here the results obtained for DDO 210, Sextans B and NGC 3109.

scholarly journals Variable star monitoring in local group dwarf irregular galaxies

2004 ◽  
Vol 193 ◽  
pp. 70-74 ◽  
Author(s):  
Jan Snigula ◽  
Claus Gössl ◽  
Ulrich Hopp ◽  
Heinz Barwig
Keyword(s):  
Variable Star ◽  
Local Group ◽  
Dwarf Galaxy ◽  
Variable Stars ◽  
Star Formation History ◽  
Stellar Content ◽  
Irregular Galaxies ◽  
Formation History ◽  
First Results ◽  
Dwarf Irregular Galaxies

AbstractDwarf galaxies in the local group provide a unique astrophysical laboratory. Despite their proximity some of these systems still lack reliable distance determinations as well as studies of their stellar content and star formation history. We present first results of our survey of variable stars in a sample of six local group dwarf irregular galaxies. Taking the Leo A dwarf galaxy as an example we describe observational strategies and data reduction. We discuss the light curves of two newly found Cepheids and place them into the context of a previously derived P-L relation. Finally we discuss the LPV content of Leo A.

scholarly journals A spatially-resolved study of initial mass function in the outer Galaxy

2016 ◽  
Vol 11 (S321) ◽  
pp. 34-36
Author(s):  
Chikako Yasui ◽  
Natsuko Izumi ◽  
Masao Saito ◽  
Naoto Kobayashi
Keyword(s):  
Mass Function ◽  
Initial Mass Function ◽  
Solar Neighborhood ◽  
High Mass ◽  
Initial Mass ◽  
Mass Detection ◽  
Spatially Resolved ◽  
Luminosity Functions ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

AbstractOutskirts of spiral galaxies, including our own, and dwarf irregular galaxies are known to have a different environment from the solar neighborhood, e.g., low metallicities ( ~ − 1 dex). Among them, the outer Galaxy is the closest and hence is so far the only site suitable for population studies of resolved stars on the same basis as solar neighborhood. We have obtained NIR images of young clusters in the outer Galaxy, using the Subaru 8.2-m telescope, and clearly resolved cluster members with mass detection limits of ~ 0.1 M⊙. Based on the fitting of K-band luminosity functions (KLFs) for four clusters, we found that the initial mass function (IMF) in the outer Galaxy is consistent with that in the solar neighborhood in terms of the high-mass slope and IMF peak. Upcoming observations with a higher spatial resolution and sensitivity, using JWST, TMT, etc., will allow us to extend spatially-resolved studies of the IMF to Local Group galaxies.

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.

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