J/A+A/669/A10 Recent star formation history of Galactic disc (Zari+, 2023)
Did the Milky Way just light up?
The recent star formation history of the Galactic disc.
Zari E., Frankel N., Rix H.-W.
<Astron. Astrophys. 669, A10 (2023)>
=2023A&A...669A..10Z 2023A&A...669A..10Z (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, early-type ; Optical
Keywords: stars: early-type - Galaxy: structure - Galaxy: disk
Abstract:
We map the stellar age distribution (≲1Gyr) across a 6kpcx6kpc area
of the Galactic disc, in order to constrain our Galaxy's recent
star-formation history. Our modelling draws on the sample of Zari et
al. (2021. Cat. J/A+A/650/A112) that encompasses all presumed disc OBA
stars (∼500000 sources) with G<16. To be less sensitive to reddening,
we do not forward model the detailed CMD distribution of these stars,
but instead the K-band absolute magnitude distribution, n(MK) among
stars with MK<0 and Teff>7000K at a certain positions {vec}x in
the disc as a step function with five age bins, b(τ|{vec}x,
{vec}α), logarithmically-spaced in age from τ=5Myr to
τ∼1Gyr. Given a set of isochrones and a Kroupa (2001) initial mass
function, we sample b(τ,|{vec}x, {vec}α) to maximise the
likelihood of the data n(MK|{vec}x, {vec}α), accounting for
the selection function. This results in a set of mono-age stellar
density maps across a sizeable portion of the Galactic disc. These
maps show that some, but not all, spiral arms are reflected in
overdensities of stars younger than 500Myr. The maps of the youngest
stars (<10Myr) trace major star forming regions. The maps at all ages
exhibit an outward density gradient and distinct spiral-like spatial
structure, which is qualitatively similar on large scales among the
five age bins. When summing over the maps' area and extrapolating to
the whole disc, we find an effective star-formation rate over the last
10Myr of ∼3.3M☉/yr, higher than previously published estimates
that had not accounted for unresolved binaries. Remarkably, our
stellar age distribution implies that the star-formation rate has been
three times lower throughout most of the last Gyr, having risen
distinctly only in the very recent past. Finally we use TNG50
simulations to explore how justified the common identification of
local age distribution with global star formation history is: we find
that the global star-formation rate at a given radius in
Milky-Way-like galaxies is approximated within a factor of ∼1.5 by the
young age distribution within a 6kpcx6kpc area near R☉.
Description:
The file table1.txt contains the α values and uncertainties for
all the spaxels.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 478 256 alpha values and uncertainties for all the spaxels
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See also:
J/A+A/650/A112 : Mapping hot luminous stars in the Galaxy (Zari+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 25 E25.19 kpc xmin Min x-coordinate of spaxel
27- 51 E25.19 kpc xmax Max x-coordinate of spaxel
53- 77 E25.19 kpc ymin Min y-coordinate of spaxel
79-103 E25.19 kpc ymax Max y-coordinate of spaxel
105-128 E24.19 yr-1 alpha1 Best fit value of coefficient alpha_1
130-153 E24.19 yr-1 b_alpha1 16th percentile of coefficient alpha_1
155-178 E24.19 yr-1 B_alpha1 84th percentile of coefficient alpha_1
180-203 E24.19 yr-1 alpha2 Best fit value of coefficient alpha_2
205-228 E24.19 yr-1 b_alpha2 16th percentile of coefficient alpha_2
230-253 E24.19 yr-1 B_alpha2 84th percentile of coefficient alpha_2
255-278 E24.19 yr-1 alpha3 Best fit value of coefficient alpha_3
280-303 E24.19 yr-1 b_alpha3 16th percentile of coefficient alpha_3
305-328 E24.19 yr-1 B_alpha3 84th percentile of coefficient alpha_3
330-353 E24.19 yr-1 alpha4 Best fit value of coefficient alpha_4
355-378 E24.19 yr-1 b_alpha4 16th percentile of coefficient alpha_4
380-403 E24.19 yr-1 B_alpha4 84th percentile of coefficient alpha_4
405-428 E24.19 yr-1 alpha5 Best fit value of coefficient alpha_5
430-453 E24.19 yr-1 b_alpha5 16th percentile of coefficient alpha_5
455-478 E24.19 yr-1 B_alpha5 84th percentile of coefficient alpha_5
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Acknowledgements:
Eleonora Zari, zari(at)mpia.de
(End) Patricia Vannier [CDS] 09-Nov-2022