Are There Age Spreads in Star Forming Regions?

Abstract

A luminosity spread at a given effective temperature is ubiquitously seen in the Hertzsprung-Russell (HR) diagrams of young star forming regions and often interpreted in terms of a prolonged period (>=10 Myr) of star formation. I review the evidence that the observed luminosity spreads are genuine and not caused by astrophysical sources of scatter. I then address whether the luminosity spreads necessarily imply large age spreads, by comparing HR diagram ages with ages from independent clocks such as stellar rotation rate, the presence of circumstellar material and lithium depletion. I argue that whilst there probably is a true luminosity dispersion, there is little evidence to support age spreads larger than a few Myr. This paradox could be resolved by brief periods of rapid accretion during the class I pre main-sequence phase.

To appear in the proceedings of JENAM10: Star Clusters in the Era of Large Surveys, 8 pages

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Cited by in corpus (7)

• The stellar population of Sco OB2 revealed by Gaia DR2 data
• The Complex Distribution of Recently Formed Stars. Bimodal Stellar Clustering in the Star-Forming Region NGC 346
• Revisiting the pre-main-sequence evolution of stars I. Importance of accretion efficiency and deuterium abundance
• The Gaia-ESO Survey and CSI 2264: Substructures, disks, and sequential star formation in the young open cluster NGC 2264
• Accretion discs as regulators of stellar angular momentum evolution in the ONC and Taurus-Auriga
• Resolved star formation in the metal poor star-forming region Magellanic Bridge C
• Stellar Evolution Models of Young Stars: Progress and Limitations