Measuring the vertical age structure of the Galactic disc using asteroseismology and SAGA
(2016) In Monthly Notices of the Royal Astronomical Society 455(1). p.987-1007- Abstract
- The existence of a vertical age gradient in the Milky Way disc has been indirectly known for long. Here, we measure it directly for the first time with seismic ages, using red giants observed by Kepler. We use Stromgren photometry to gauge the selection function of asteroseismic targets, and derive colour and magnitude limits where giants with measured oscillations are representative of the underlying population in the field. Limits in the 2MASS system are also derived. We lay out a method to assess and correct for target selection effects independent of Galaxy models. We find that low-mass, i. e. old red giants dominate at increasing Galactic heights, whereas closer to the Galactic plane they exhibit a wide range of ages and... (More)
- The existence of a vertical age gradient in the Milky Way disc has been indirectly known for long. Here, we measure it directly for the first time with seismic ages, using red giants observed by Kepler. We use Stromgren photometry to gauge the selection function of asteroseismic targets, and derive colour and magnitude limits where giants with measured oscillations are representative of the underlying population in the field. Limits in the 2MASS system are also derived. We lay out a method to assess and correct for target selection effects independent of Galaxy models. We find that low-mass, i. e. old red giants dominate at increasing Galactic heights, whereas closer to the Galactic plane they exhibit a wide range of ages and metallicities. Parametrizing this as a vertical gradient returns approximately 4 Gyr kpc(-1) for the disc we probe, although with a large dispersion of ages at all heights. The ages of stars show a smooth distribution over the last similar or equal to 10 Gyr, consistent with a mostly quiescent evolution for the Milky Way disc since a redshift of about 2. We also find a flat age-metallicity relation for disc stars. Finally, we show how to use secondary clump stars to estimate the present-day intrinsic metallicity spread, and suggest using their number count as a new proxy for tracing the ageing of the disc. This work highlights the power of asteroseismology for Galactic studies; however, we also emphasize the need for better constraints on stellar mass-loss, which is a major source of systematic age uncertainties in red giant stars. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/8748012
- author
- Casagrande, L.
; Aguirre, V. Silva
; Schlesinger, K. J.
; Stello, D.
; Huber, D.
; Serenelli, A. M.
; Schoenrich, R.
; Cassisi, S.
; Pietrinferni, A.
; Hodgkin, S.
; Milone, A. P.
; Feltzing, Sofia
LU
and Asplund, M.
(Less) - organization
- publishing date
- 2016
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- asteroseismology, stars: distances, stars: fundamental parameters, stars: general, Galaxy: disc, Galaxy: evolution
- in
- Monthly Notices of the Royal Astronomical Society
- volume
- 455
- issue
- 1
- pages
- 987 - 1007
- publisher
- Oxford University Press
- external identifiers
-
- wos:000368005900099
- scopus:84958193322
- ISSN
- 1365-2966
- DOI
- 10.1093/mnras/stv2320
- project
- The Strömgren survey for Asteroseismology and Galactic Archeology
- language
- English
- LU publication?
- yes
- id
- 4f36e20c-eee7-40df-9eb2-7b09da80ec29 (old id 8748012)
- date added to LUP
- 2016-04-01 10:29:00
- date last changed
- 2024-04-21 14:26:32
@article{4f36e20c-eee7-40df-9eb2-7b09da80ec29,
abstract = {{The existence of a vertical age gradient in the Milky Way disc has been indirectly known for long. Here, we measure it directly for the first time with seismic ages, using red giants observed by Kepler. We use Stromgren photometry to gauge the selection function of asteroseismic targets, and derive colour and magnitude limits where giants with measured oscillations are representative of the underlying population in the field. Limits in the 2MASS system are also derived. We lay out a method to assess and correct for target selection effects independent of Galaxy models. We find that low-mass, i. e. old red giants dominate at increasing Galactic heights, whereas closer to the Galactic plane they exhibit a wide range of ages and metallicities. Parametrizing this as a vertical gradient returns approximately 4 Gyr kpc(-1) for the disc we probe, although with a large dispersion of ages at all heights. The ages of stars show a smooth distribution over the last similar or equal to 10 Gyr, consistent with a mostly quiescent evolution for the Milky Way disc since a redshift of about 2. We also find a flat age-metallicity relation for disc stars. Finally, we show how to use secondary clump stars to estimate the present-day intrinsic metallicity spread, and suggest using their number count as a new proxy for tracing the ageing of the disc. This work highlights the power of asteroseismology for Galactic studies; however, we also emphasize the need for better constraints on stellar mass-loss, which is a major source of systematic age uncertainties in red giant stars.}},
author = {{Casagrande, L. and Aguirre, V. Silva and Schlesinger, K. J. and Stello, D. and Huber, D. and Serenelli, A. M. and Schoenrich, R. and Cassisi, S. and Pietrinferni, A. and Hodgkin, S. and Milone, A. P. and Feltzing, Sofia and Asplund, M.}},
issn = {{1365-2966}},
keywords = {{asteroseismology; stars: distances; stars: fundamental parameters; stars: general; Galaxy: disc; Galaxy: evolution}},
language = {{eng}},
number = {{1}},
pages = {{987--1007}},
publisher = {{Oxford University Press}},
series = {{Monthly Notices of the Royal Astronomical Society}},
title = {{Measuring the vertical age structure of the Galactic disc using asteroseismology and SAGA}},
url = {{http://dx.doi.org/10.1093/mnras/stv2320}},
doi = {{10.1093/mnras/stv2320}},
volume = {{455}},
year = {{2016}},
}