The effects of unresolved binary stars on the determination of the stellar mass function

Kroupa, Pavel; Tout, Christopher A.; Gilmore, G.

doi:10.1093/mnras/251.2.293

Cited by 134 publications

(134 citation statements)

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“…First, neither local peaks shown in Trapezium ( Hillenbrand 1997) nor dips seen in the field and open clusters (Kroupa et al 1990) are clearly exhibited in these JLFs regardless of the extinction limit. Second, a turnover as seen in the Scalo (1986) IMF of the stellar population in the solar neighborhood does not occur.…”

Section: Luminosity Functions Of the Three Groupsmentioning

confidence: 89%

“…On the other hand, the number of low-mass stars and BDs will be underestimated depending on the binary proportion. A single-star LF ( MF) may be somewhat steeper than one in which unresolved binaries are not accounted for (Kroupa et al 1991;Kroupa 2001). If we assume all groups have the same binary fraction, these LFs can be compared without correction for binaries.…”

Section: Luminosity Functions Of the Three Groupsmentioning

confidence: 99%

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Very Low Luminosity Young Cluster and the Luminosity and Mass Functions in S106

et al. 2006

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We present the results of deep near-infrared observations searching for very low mass young stellar objects (YSOs) in the massive star-forming region of S106 taken with the Subaru Telescope. The survey, whose limiting magnitude exceeds 20 mag in the JHK 0 bands, is sensitive enough to provide unprecedented details in the two nebular lobes. In addition, it reveals a census of the stellar population down to objects below the deuterium-burning limit, a fiducial boundary between brown dwarfs and planetary-mass objects. Based on color-color diagrams, nearly 600 embedded YSO candidates with near-infrared excesses have been identified in an area of $5 0 ; 5 0 that are not uniformly distributed but centrally concentrated. Combining the reddening-corrected luminosity of the YSO candidates with the theoretical evolutionary models, we suggest that there exists a substantial substellar population. If we divide the cluster into three subgroups based on stellar and cloud properties, both their luminosity functions and mass functions across the stellar-substellar boundary demonstrate local variation on a subparsec scale. Nevertheless, all the mass functions have distinct characteristics in common: they do not have any turnover and do not decline down to the completeness limits. Furthermore, the mass function for S106 appears to be more abundant in young substellar objects compared to those obtained for other young clusters, such as Trapezium and IC 348. This implies that the substellar mass function for young clusters may have a variation.

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Section: Luminosity Functions Of the Three Groupsmentioning

confidence: 89%

Section: Luminosity Functions Of the Three Groupsmentioning

confidence: 99%

Very Low Luminosity Young Cluster and the Luminosity and Mass Functions in S106

et al. 2006

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“…We note that for the Milky Way IMF, current data cannot significantly differentiate between these two function forms (Kroupa et al 2013). The shape of the IMF is somewhat degenerate with the presence of unresolved binary stars (Kroupa et al 1991). We have therefore opted to fit both the IMF shape and the binary fraction simultaneously.…”

Section: Constructing the Model Imfsmentioning

confidence: 99%

The Stellar Initial Mass Function of Ultra-Faint Dwarf Galaxies: Evidence for Imf Variations With Galactic Environment

Geha

Brown

Tumlinson

et al. 2013

ApJ

195

229

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We present constraints on the stellar initial mass function (IMF) in two ultra-faint dwarf (UFD) galaxies, Hercules and Leo IV, based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. The Hercules and Leo IV galaxies are extremely low luminosity (M V = −6.2, −5.5), metal-poor ( [Fe/H] = −2.4, −2.5) systems that have old stellar populations (>11 Gyr). Because they have long relaxation times, we can directly measure the low-mass stellar IMF by counting stars below the main-sequence turnoff without correcting for dynamical evolution. Over the stellar mass range probed by our data, 0.52-0.77 M , the IMF is best fit by a power-law slope of α = 1.2 +0.4 −0.5 for Hercules and α = 1.3 ± 0.8 for Leo IV. For Hercules, the IMF slope is more shallow than a Salpeter (α = 2.35) IMF at the 5.8σ level, and a Kroupa (α = 2.3 above 0.5 M ) IMF slope at 5.4σ level. We simultaneously fit for the binary fraction, f binary , finding f binary = 0.47 +0.16 −0.14 for Hercules, and 0.47 +0.37 −0.17 for Leo IV. The UFD binary fractions are consistent with that inferred for Milky Way stars in the same mass range, despite very different metallicities. In contrast, the IMF slopes in the UFDs are shallower than other galactic environments. In the mass range 0.5-0.8 M , we see a trend across the handful of galaxies with directly measured IMFs such that the power-law slopes become shallower (more bottom-light) with decreasing galactic velocity dispersion and metallicity. This trend is qualitatively consistent with results in elliptical galaxies inferred via indirect methods and is direct evidence for IMF variations with galactic environment.

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“…We find that a large proportion of unresolved binary systems can explain the difference between photographically determined luminosity functions and the nearby luminosity function (Kroupa et al 1991, Kroupa 1992, as shown in Fig where m is the stellar mass in solar units, a « 1.2 and £(m)dm is the number of stars per pc 3 in the mass range m to m + dm. The hydrogen-burning limit is taken to be Q.Q%M®.…”

Section: B I N a R Y S T A R Smentioning

confidence: 57%

The Stellar Luminosity Function and Binary Stars

Kroupa

Tout

Gilmore

1992

International Astronomical Union Colloquium

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ABSTRACT:If all stars within a small volume surrounding the sun are counted we obtain an approximation of the low-mass single-star luminosity function. Alternatively, deep photographic surveys cannot resolve most of the binary systems, and consequently we obtain an approximation to the system luminosity function. Comparing the singlestar and system luminosity functions we derive the stellar mass function and constrain the properties of binary systems.

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The effects of unresolved binary stars on the determination of the stellar mass function

Cited by 134 publications

References 0 publications

Very Low Luminosity Young Cluster and the Luminosity and Mass Functions in S106

Very Low Luminosity Young Cluster and the Luminosity and Mass Functions in S106

The Stellar Initial Mass Function of Ultra-Faint Dwarf Galaxies: Evidence for Imf Variations With Galactic Environment

The Stellar Luminosity Function and Binary Stars

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