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RIOJA. Dusty outflows and density-complex ISM in the N-enhanced lensed galaxy RXCJ2248-ID at z=6.1

A. Crespo Gómez, Y. Tamura, L. Colina, J. Álvarez-Márquez, T. Hashimoto, R. Marques-Chaves, Y. Nakazato, C. Blanco-Prieto, K. Sunaga, L. Costantin, A. K. Inoue, A. Hamada, S. Arribas, D. Ceverino, M. Hagimoto, K. Mawatari, W. Osone, Y. Sugahara, Y. Harikane, M. M. Lee, A. Taniguchi, H. Umehata

Abstract

We present an analysis on the kinematics and physical properties of the ionized gas in the lensed galaxy RXCJ2248-ID at z=6.1 based on high-resolution JWST NIRSpec/IFU data in combination with ALMA observations. Our analysis reveals a high electron temperature ($T_e$$\sim$30000K) in the ionized gas, independent of the ionization level. We measure a wide range in the electron densities derived from [OIII]$λ$5008/[OIII]88$μ$m and [ArIV]$λ$4713/[ArIV]$λ$4742 ratios (log($n_e$[cm$^{-3}$])$\sim$2.7-3.8), and previous values (log($n_e$[cm$^{-3}$])>4.8) based on high-ionization rest-UV emission lines. The ionized gas appears to be clumpy with a low filling factor ranging from about 10% to 0.2% for the low- and high-density clouds. In addition, we observe a very complex ISM kinematic structure, with the presence of two distinct broad and a very-broad components (FWHM$\sim$210 and $\sim$1000 kms$^{-1}$) in addition to the systemic one (FWHM$\sim$60 kms$^{-1}$) in [OIII]$λ$5008 and H$α$. These broad components are heavily extinct (A$_V$$\sim$1.5 and 2.5, respectively), based on their Balmer decrements, while the gas associated to the narrow component is consistent with no extinction. The maximal velocities of these outflows ($\sim$115-500kms$^{-1}$) are such that a fraction of the total outflowing gas (0.16-2.1$\times$10$^7$M$_\odot$) could escape into the IGM. The rest of the gas will fall back to the central regions, being available for additional star formation episodes. The presence of dusty outflows and clumpy (i.e., low filling factor) ISM give support to the Attenuation-Free scenario proposed to explain the high-z UV-bright compact galaxies such as RXCJ2248-ID. On the other hand, the high densities in the ISM, together with the high SFR surface brightness, and the amount of returning outflowing mass give support to the Feedback-Free Starburst scenario.

RIOJA. Dusty outflows and density-complex ISM in the N-enhanced lensed galaxy RXCJ2248-ID at z=6.1

Abstract

We present an analysis on the kinematics and physical properties of the ionized gas in the lensed galaxy RXCJ2248-ID at z=6.1 based on high-resolution JWST NIRSpec/IFU data in combination with ALMA observations. Our analysis reveals a high electron temperature (30000K) in the ionized gas, independent of the ionization level. We measure a wide range in the electron densities derived from [OIII]5008/[OIII]88m and [ArIV]4713/[ArIV]4742 ratios (log([cm])2.7-3.8), and previous values (log([cm])>4.8) based on high-ionization rest-UV emission lines. The ionized gas appears to be clumpy with a low filling factor ranging from about 10% to 0.2% for the low- and high-density clouds. In addition, we observe a very complex ISM kinematic structure, with the presence of two distinct broad and a very-broad components (FWHM210 and 1000 kms) in addition to the systemic one (FWHM60 kms) in [OIII]5008 and H. These broad components are heavily extinct (A1.5 and 2.5, respectively), based on their Balmer decrements, while the gas associated to the narrow component is consistent with no extinction. The maximal velocities of these outflows (115-500kms) are such that a fraction of the total outflowing gas (0.16-2.110M) could escape into the IGM. The rest of the gas will fall back to the central regions, being available for additional star formation episodes. The presence of dusty outflows and clumpy (i.e., low filling factor) ISM give support to the Attenuation-Free scenario proposed to explain the high-z UV-bright compact galaxies such as RXCJ2248-ID. On the other hand, the high densities in the ISM, together with the high SFR surface brightness, and the amount of returning outflowing mass give support to the Feedback-Free Starburst scenario.

Paper Structure

This paper contains 23 sections, 8 figures, 5 tables.

Table of Contents

  1. Introduction
  2. Observations and data calibration
  3. NIRSpec IFS observation
  4. [OIII] 88$\mu$m ALMA observations
  5. Complementary NIRCam images
  6. Astrometric alignment
  7. Data processing and analysis
  8. Aperture extraction and line fluxes
  9. Deblending of [ArIV] $\lambda$4713 + He I 4714 lines
  10. Results
  11. Kinematic substructure in the ionised ISM
  12. Dynamical versus stellar mass
  13. Dust distribution in the ionised ISM
  14. Electron temperature
  15. Electron density
  16. ...and 8 more sections

Figures (8)

  • Figure 1: NIRCam F115W and F444W, NIRSpec/[OIII] $\lambda$5008 and RGB (F115W/F200W/F444W) cutouts for RXCJ2248-ID3. Blue contours show the F115W emission. White and green circles represent the 'total' and 'nuclear' apertures used to extract the integrated spectra, respectively. White circles (ellipse) in the lower right corners display the FWHM (beam size) for the NIRCam/NIRSpec (ALMA) data. White contours in the RGB image represent the [OIII] 88$\mu$m emission integrated over 477.27 $-$ 477.75 GHz. The contours are drawn at 2, 3, 4 and 5$\sigma$, where $\sigma = 70$ mJy km s$^{-1}$ beam$^{-1}$.
  • Figure 2: Observed spectra for the 'nuclear' and 'total' apertures. The zoom-in sub-panels show the main emission lines detected in this work. Grey areas mark the spectral regions affected by the detector gap in NIRSpec.
  • Figure 3: Multiple Gaussian analysis performed in the observed [OIII] $\lambda$5008 and H$\alpha$ + [NII] $\lambda$6550, 6585 lines extracted from the 'nuclear' aperture (see Sect. \ref{['subsec:Kin']}). Solid black and red lines represent the observed line and its best-fit model, while the narrow, broad and very-broad components are shown in doted-dashed green, and dashed blue and orange lines, respectively. In the lower panels, black diamonds show the residuals between the best-fit model and the observed line profiles, where the grey shadow area represents the 3$\sigma$ noise derived during the fitting procedure (see Sect. \ref{['subsec:int_spec']}). For comparison, pink squares represent the residuals assuming 2 Gaussian profiles for the [OIII] $\lambda$5008 and H$\alpha$ lines. Each panel contains a zoom-in inset to display the contribution of the broad and very broad components to the line profiles.
  • Figure 4: Electron density and temperature diagnosis. The green line and shadowed area show the ratio [ArIV] $\lambda$4713/[ArIV] $\lambda$4742 and its uncertainty derived after deblending the HeI $\lambda$4714 contribution (see Sect \ref{['subsec:deblending']}). Similarly, orange and blue lines and shadowed areas represent the [OIII] $\lambda$4364/[OIII] $\lambda$5008 and [OIII] $\lambda$5008/[OIII] $\lambda$88 ratios which trace the $T_\mathrm{e}$ and $n_\mathrm{e}$, respectively.
  • Figure 5: Illustration of the model proposed assuming a generally spherical but anisotropic distribution. Blue, gold and red clouds represent three different ISM layers that we linked to the kinematic components found in Sect. \ref{['subsec:Kin']}. In addition, we include a more diffuse component (in yellow) corresponding to [OIII] 88$\mu$m emission ($n_\mathrm{e}$$\sim$ 500 cm$^{-3}$). In this model, the narrow component is emitted from the inner and more dense regions (in blue), while the dusty outflowing gas lie at larger distances (gold and red).
  • ...and 3 more figures