The influence of tight binaries on proto-planetary disk masses

TL;DR

This study quantifies how tight ( $<10$ au) binary companions influence planet-forming disk material by surveying over 100 spectroscopic binaries in Orion A with ALMA. Dust masses are derived for 107 clean targets, with 21 showing significant continuum emission, revealing a median disk dust mass of $11.6\ M_{\oplus}$ and a maximum of $95.5\ M_{\oplus}$; HCO$^+$ gas masses are measured for six disks. The tight-binary disk population is depleted in dust mass by roughly a factor of $2$ compared with several single-star young clusters, with robust statistics (e.g., $p<0.005$ against Lupus, Cham I, Taurus), though not against the ONC, suggesting environmental influences like photoevaporation may play a role. Infrared analysis indicates the inner disks around these binaries are not uniformly cleared, as IR excesses are common, but systems lacking ALMA detections tend to have weaker $3$–$5\,\mu$m excesses, consistent with partial depletion of warm dust. The results imply reduced planet-forming potential in tight binaries and point to multiple contributing mechanisms—intrinsic disk properties, formation pathways, or sample biases—that warrant further investigation.

Abstract

Binary systems are a common site of planet formation, despite the destructive effects of the binary on the disk. While surveys of planet forming material have found diminished disk masses around medium separation ($\sim$10--100 au) binaries, less is known about tight ($<$10 au) binaries, where a significant circumbinary disk may escape the disruptive dynamical effects of the binary. We survey over 100 spectroscopic binaries in the Orion A region with ALMA, detecting significant continuum emission among 21 of them with disk masses ranging from 1--100 M$_{\oplus}$. We find evidence of systematically lower disk masses among the binary sample when compared to single star surveys, which may reflect a diminished planet forming potential around tight binaries. The infrared excess fraction among the binary sample is comparable to single stars, although the tight binaries without significant ALMA emission display tentative evidence of weaker 3-5$μ$m excesses. The depletion of cold dust is difficult to explain by clearing alone, and the role of additional mechanisms needs to be explored. It may be the result of the formation pathway for these objects, systematic differences in intrinsic properties (e.g., opacity) or a bias in how the sample was constructed.

Figures (6)

• Figure 1: Location of our tight binary targets on a map of dust extinction schlegel1998. Green circles indicate the targets of our ALMA observations that made it through the cluster membership cuts (section \ref{['sec:cleaning']}). The majority of our targets are located near the Orion Nebula Cluster, with some spread along the Orion A cloud; the more isolated targets in Orion A are marked with their ID numbers.
• Figure 2: Continuum images, centered on the detections, of cluster members. Each panel is 6$^{\prime\prime}$ on a side, with the scale bar in units of mJy bm$^{-1}$.
• Figure 3: Membership diagnostics among the sources in our survey. We employ cuts on parallax ($p$) and proper motion ($\mu_{\alpha}$, $\mu_{\delta}$) to remove interlopers; these boundaries are indicated by solid black lines. RV is not used to remove non-cluster members as it may be biased by the presence of a binary. Many of the sources identified as interlopers by their discrepant parallax and/or proper motion values also fall outside the pre-main sequence region in the $\log~g$ vs $T_{\rm eff}$ diagram, enclosed by the solid lines, confirming their status as interlopers.
• Figure 4: HCO$^+$ detections, including moment 0 maps (in units of Jy bm$^{-1}$ km s$^{-1}$), and spectra (in the barycentric reference frame, and in units of Jy)). Cloud contamination is present in some of the spectra at v$_{\rm bary}\sim$30 km s$^{-1}$. Dotted contours in the moment 0 maps are at 3, 5, 10, and 20$\sigma$. Grey bands indicate the $\pm$1 $\sigma$ ranges for the stellar velocities as measured in optical spectra by Kounkel2019. Red dashed lines show model disk emission for comparison, generated using parametric models as described in Appendix \ref{['sec:hcoplus_models']}.
• Figure 5: Disk dust mass distribution for the tight binaries from our sample and as compared with the ONC eisner2018 and Orion vanTerwisga2022 (left panel) and the young clusters Lupus, Cham I , and Taurus (data compiled by manara2022, right panel). The disk masses around tight binaries are significantly depleted relative to the single stars in Orion and Lupus/Cham I/Taurus, and are comparable to those around stars in the ONC, which exhibits a depletion from photoevaporation from nearby massive stars.