LAMOST Medium-resolution Spectroscopic Survey of the Rosette Nebula

TL;DR

This study delivers the most extensive spatially resolved spectroscopic dataset for the Rosette Nebula to date, using LAMOST MRS-N to obtain 3854 nebular spectra over 4.52 deg^2 and measure Hα, [N II], and [S II] lines. Instrumental broadening is corrected via $FWHM_{real}^2 = FWHM_{obs}^2 - FWHM_{inst}^2$, enabling robust RVs, FWHMs, and line-intensity maps; a bow-shaped RV feature and a possible interaction with the Monoceros Loop SNR emerge from the velocity field, complemented by kinematic-distance estimates around 1.5 kpc. The work reports spatial gradients in line intensities, gas temperature near $T \approx 8000$ K, and turbulent velocities from $V_t \sim 10$–40 km s$^{-1}$, with broader widths in high-dynamic regions. The compiled parameter table provides essential constraints for chemo-dynamical modeling of this H II region, advancing understanding of feedback between massive stars, the ISM, and SNRs.

Abstract

We report multi-fiber, medium-resolution spectroscopy of the Rosette Nebula with full spatial coverages, and present a table of the nebular parameters based on the spatially-resolved measurements of emission lines. These new observations were conducted through the Medium-Resolution Spectroscopic Survey of Nebulae (MRS-N) on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Comprehensive analyses were performed on a total of 3854 high-quality nebular spectra, so far the most extensive spectral dataset available for this nebula that encompasses an area of 4.52 square degrees. Various physical parameters, including relative line intensities, radial velocities (RVs), and full widths at half maximum (FWHMs), were derived through measurements of the H-alpha, [N II] 6548,6584 and [S II] 6716,6731 emission lines detected in the LAMOST MRS-N spectra. For the first time, we found a bow-shaped feature in the spatial distribution of RVs of the Rosette Nebula. Moreover, the spatial distributions of RVs and FWHMs, as well as additional parameters such as gas temperature and turbulent velocity in the vicinity of the nebula, indicate possible interaction between Rosette and the nearby supernova remnant (SNR), Monoceros Loop. Our new observations provide indispensable measurements of the Rosette Nebula. The parameter table in particular can be used as valuable constraint on the chemo-dynamical modeling of the nebula, which will enable deeper understanding of the characteristics of this H II region.

Figures (7)

• Figure 1: LAMOST medium-resolution spectra of the Rosette Nebula extracted from three different fiber positions, showing the highest data quality with S/N([S ii])$>$60 (top panel, representing the majority of the fiber spectra reported in this work), medium data quality with S/N([S ii])$\simeq$40 (middle panel), and relatively low data quality with S/N([S ii])$\simeq$10. The spectra are all normalized such that the integrated flux $F$(H$\alpha$) = 300 (given that the theoretical intensity ratio H i H$\alpha$/H$\beta$ = 2.85 HIcoe combined with Galactic extinction). The vertical ranges of the three panels are set to accommodate the intensity of H$\alpha$.
• Figure 2: The histogram (panel a) and the spatial distribution (panel b) of the S/N ratio of H$\alpha$ as measured from the fiber spectra of the Rosette Nebula. Within the optical boundary of the nebula, the S/N's are mostly $>$100.
• Figure 3: The histograms (panel a) and 2D spatial distributions of the relative intensities of H$\alpha$ (panel b), [N ii] (panel c), and [S ii] (panel d). In panel (a), the number peaks of the distributions of the three emission lines are marked by vertical dashed lines, with the same color-coding as the histograms. Note that the color scales for panels b, c and d are the same.
• Figure 4: The histograms (panel a) and 2D spatial distributions of the RVs (in km s$^{-1}$) measured with H$\alpha$ (panel c), [N ii] (panel d) and [S ii] (panel e). Panel (b) shows the Gaussian-profile fits of the three histograms in panel (a). Panel (f) shows the error of RVs (in km s$^{-1}$) measured in three regions shown in panel (c). Notably, the value of error in the northeast region is larger than in other parts of the nebula.
• Figure 5: The histogram (panel a) and 2D spatial distribution (panel b) of the kinematic distance (in unit of kpc) measured with the H$\alpha$ emission line.