UN-TARGETED STUDIES OF MASSIVE STARS IN LOCAL GROUP ...

UN-TARGETED STUDIES

OF MASSIVE STARS IN

LOCAL GROUP GALAXIES

WITH BlueMUSE

MIRIAM GARCIA

WHY LOW-Z (sub-SMC) MASSIVE STARS?

Processes that rule the physics of massive stars at the peak of star

formation and higher redshift.

Feedback throughout Cosmic History

Map of progenitors of GRBs, SNe, SLSNe

Formation of >30M

black holes in binary systems (GW150914)

Working towards the First Stars

Mad

au

& D

ickin

so

n

(2014)

SMC

METAL-POOR GALAXIES OF THE LOCAL GROUP

Decreasing metallicity

IC1613,

NGC3109,

WLM

1/7 O

750Kpc

SEXTANS-A

1/10 Z

1.3Mpc

SMC

1/5 Z

60 Kpc

LMC

2/5 Z

50 Kpc

3

SPECIAL EVOLUTIONARY CHANNELS AT VERY LOW-Z

Chemically homogeneous evolution (CHE)

Szécsi+ 2015

(see also e.g. Schaerer 2002)

TWUINs:

90 000 K

10-20 R

10 000 000 L

H-burning

4

Evolutionary tracks for 1/50 Z

Szécsi+ 2015



294M

MS average (1.9Myr)

L(H) =2.58E40 erg/s

L(HeI)=1.31E40 erg/s

L(HeII)=6.82E38 erg/s

Kehrig+ 2015

TWUINs proposed to explain

intense HeII4686 emission in

IZw18 (Kehrig+ 2015), CR7

(Sobral+ 2015) 5




TWUINs:

6


CHE: a possible channel to form ~30+30 M

binary black holes

(Mandel & de Mink 2016, Marchant+ 2016, duBuisson+ 2020)

CHE: star remains compact and does not overflow Roche lobe

Low-Z: weaker winds and higher masses at the end of evolution



TWUINs:

7


Observational confirmation needed

Census of complete populations in very

low-Z galaxies.

LOW-Z INITIAL MASS FUNCTION AND

MAXIMUM STELLAR MASS

30 Doradus, LMC (2/5Z

) GS2, IC1613 (1/7O

)

250M 60M

8

Sextans-A (1/10Z

)

Bestenlehner+ 2020

See also Crowther+ 2010

Garcia+ 2017

Need to complete census in target

galaxies

STAR FORMATION IN THE OUTSKIRTS OF SEXTANS-A

9

Garcia+ 2019

47M

24M

31M

17M

HI gas density at the limit for

star formation:

NHI=1 E21 cm-2

(Skillman1987, Ott+ 2012)

Stars are isolated: stochastic

sampling of the IMF?

Connection with extended UV-disk

galaxies?

(Gil de Paz+ 2005, Thilker+ 2005)

GRBs y SLSNe preferencially

found in the external parts of

low-Z dwarf galaxies

(e.g. Michałowski+ 2015)

Need to look for massive stars in all

galactic environments with deep, high

spatial resolution observations.

WIDE-FIELD IFUs KEY TO STUDY THE FORMATION &

EVOLUTION OF LOW-Z MASSIVE STARS

Leo-P

10

Sextans A

Total coverage

•Biases against certain galactic locations, avoided

High multiplexing

Untargeted searches:

•Biases against certain evolutionary stages, avoided

•Minimize targets lost to internal galactic extinction

11

Lorenzo, Garcia, et al. in prep

Sextans-A:

GTC-OSIRIS

R= / = 1000; 4000-5000 Å

Reddened

massive stars

12


Sextans-A:

GTC-OSIRIS

R= / = 1000; 4000-5000 Å

Extinction

correction thanks

to spectral typing

13


Sextans-A:

GTC-OSIRIS

R= / = 1000; 4000-5000 Å

TECHNICAL CONSIDERATIONS

14

50 M

MUSE expected flux

for an O-type star

BlueMUSE: sufficient SNR to constrain

vrot and abundances, only for V<20.

BlueMUSE enhanced

sensitivity in the blue makes it

optimal to study blue massive

stars in low-Z galaxies.

First hints of mixing processes at

sub-SMC metallicity

(only the brightest stars)

BlueMUSE WILL OPEN A NEW ERA IN THE STUDIES OF

SUB-SMC METALLICITY MASSIVE STARS

The wide Field of View will enable full coverage of metal-poor,

dwarf irregular galaxies of the Local Group.

The untargeted studies allow us to

• Constrain observationally the evolutionary sequence of low-Z

massive stars, and obtain first observational proof of theoretical-

proposed evolutionary stages.

• Study the IMF and maximum mass in different environments of the

host galaxies, which will shed new light on star-formation

processes at low-Z.

The blue spectral coverage is optimal to constrain the stellar

parameters of blue massive stars.

Thank you!

15

UN-TARGETED STUDIES OF MASSIVE STARS IN LOCAL GROUP ...

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