[論文レビュー] Accretion onto the Embedded Protostar L1527 IRS: Insights from JWST NIRSpec and MIRI Observations

W. Blake Drechsler, John J. Tobin+13 more|arXiv (Cornell University)|Mar 3, 2026

Astrophysics and Star Formation Studies被引用数 0

ひとこと要約

The paper uses JWST NIRSpec and MIRI IFU data to detect hydrogen lines and other species in L1527 IRS, estimating its accretion luminosity and rate and discussing magnetospheric versus boundary layer accretion in this Class 0 protostar.

ABSTRACT

Accretion is the primary driver of protostellar evolution, regulating mass assembly and shaping the physical and chemical environments of young stellar objects. Quantifying accretion in the Class 0 protostellar phase is particularly important, yet remains observationally challenging due to high extinction toward the central protostars. In this paper, we present JWST NIRSpec and MIRI/MRS IFU data towards the Class 0 protostar L1527 IRS. We extract one-dimensional spectra and find emission from atomic and molecular hydrogen, water, OH, and several ionic species. The atomic hydrogen lines, Br$α$, Pf$α$, and Pf$γ$ are the most critical to this study since they can be used as accretion diagnostics. The existence of these atomic hydrogen lines viewed in scattered light indicates that accretion is likely occurring magnetospherically rather than through a boundary layer. Moment 0 emission maps show that the hydrogen emission is co-spatial with the scattered light continuum with a strong east-west asymmetry which is not due to outflow shocks. We additionally present moment 0 maps of other detected species and discuss their emission morphology. By primarily analyzing the Br$α$ line, the strongest of our detected atomic hydrogen lines, we characterize the accretion onto L1527 IRS by estimating the accretion luminosity to be $0.4~ ext{L}_\odot$ and the accretion rate to be around $1 imes10^{-7}~ ext{M}_\odot ext{yr}^{-1}$. We lastly discuss the implications of our results with respect to both non-steady and asymmetric accretion possibly occurring in L1527 IRS.

研究の動機と目的

• Quantify accretion in the deeply embedded Class 0 protostar L1527 IRS using infrared tracers.
• Determine whether accretion proceeds via a magnetosphere or a boundary layer by analyzing hydrogen line emission and morphology.
• Map spatial distribution of detected species to distinguish scattered-light accretion signatures from shock-excited emission.
• Estimate accretion luminosity and mass accretion rate from Br-alpha and related hydrogen lines.
• Discuss implications for non-steady and asymmetric accretion in L1527 IRS.

提案手法

• Observe L1527 IRS with JWST NIRSpec (G395M) and MIRI MRS in IFU mode to obtain spectra and line maps.
• Extract 1D spectra using eastern and western disk-side apertures to maximize S/N and examine spatial variation.
• Create continuum-subtracted line cubes by fitting local continua and subtracting them to derive line fluxes.
• Analyze line profiles and moments (moment 0/1 maps) to assess emission morphology and kinematics.
• Compare Br-alpha with Pf-alpha and Pf-gamma to test consistency and infer accretion origin (magnetospheric vs boundary layer).
• Estimate intrinsic Br-alpha luminosity and derive accretion luminosity and accretion rate using standard relations.

実験結果

リサーチクエスチョン

• RQ1 Can Br-alpha, Pf-gamma, and Pf-alpha hydrogen lines be used to trace accretion in this deeply embedded Class 0 protostar?
• RQ2 Is the observed atomic hydrogen emission primarily scattered light from accretion regions, or produced locally by shocks/outflows?
• RQ3 What are the accretion luminosity and mass accretion rate of L1527 IRS, and what do they imply about the accretion mechanism?
• RQ4 How do the morphologies of H2, OH, H2O, and ionic species relate to outflow cavities and disk/envelope structure?
• RQ5 Do the JWST observations support non-steady or asymmetric accretion in L1527 IRS?

主な発見

• Hydrogen lines Br-alpha, Pf-gamma, and Pf-alpha are detected; Br-alpha is strongest and co-spatial with scattered continuum, supporting magnetospheric accretion signatures.
• Line-to-continuum analysis indicates Br-alpha emission is likely observed in scattered light, consistent with accretion tracing rather than local shocks for Br-alpha.
• Intrinsic Br-alpha luminosity yields an accretion luminosity of ~0.4 L_sun and an accretion rate of ~1e-7 M_sun/yr for L1527 IRS.
• H2 emission traces wide-angle outflows and inner cavity walls with multiple transitions showing east-west asymmetries and varied morphologies across transitions.
• Ions ([Ar II], [Ne III], [Fe II]) exhibit outflow-like morphologies with velocity gradients of ~20–40 km/s, indicating ionized cavity structures distinct from H2 shock-traced emission.
• Water and OH emissions are weaker; OH peaks near the eastern continuum, while water peaks on the western side, suggesting anti-correlated emission regions.