PREPRINT

Nuclear Activity in the Low Metallicity Dwarf Galaxy SDSS J0944-0038: A Glimpse into the Primordial Universe

Michael Reefe, Shobita Satyapal, Remington O. Sexton, Nathan J. Secrest, William Matzko, Emma Schwartzman, Kristina Nyland, Gabriela Canalizo, Barry Rothberg, Ryan W. Pfeifle, Jenna M. Cann, Archana Aravindin, Camilo Vasquez, Tracy Clarke

Submitted on 23 November 2022

Figures are fetched from the INSPIRE database at: https://inspirehep.net/literature/2514360

Top panel: Hubble Space Telescope image of J0944$-$0038, constructed from UV (F336W, blue channel), H$\alpha$ (F657N, green channel), and visual/near-IR (F814W, red channel) archival data. Bottom panel: stellar mass distribution of the subset of dwarf galaxies in the CLASS sample compared to the samples of AGNs identified by \citet{2013ApJ...775..116R} and \citet{2021ApJ...922..155M}. The stellar mass of J0944$-$0038, and other coronal line emitters, is significantly lower than the mass regime probed by traditional optical narrow line ratios.
Figure 1: Top panel: Hubble Space Telescope image of J09440038, constructed from UV (F336W, blue channel), Hα (F657N, green channel), and visual/near-IR (F814W, red channel) archival data. Bottom panel: stellar mass distribution of the subset of dwarf galaxies in the CLASS sample compared to the samples of AGNs identified by \citet{2013ApJ...775..116R} and \citet{2021ApJ...922..155M}. The stellar mass of J09440038, and other coronal line emitters, is significantly lower than the mass regime probed by traditional optical narrow line ratios.
\textit{Top Left:} The [\ion{Fe}{10}] $\lambda$6374 emission line flux map. \textit{Top Right:} [\ion{O}{3}] $\lambda$5007 flux map. \textit{Bottom Left:} The H$\alpha$ flux map. \textit{Bottom Right:} The continuum at $\lambda$5100  flux map. The red crosses in each image correspond to the positions of the peak continuum for the two brightest central clumps. Scale bars in kpc and arcseconds are given in the top left of each plot.  The color scales for [\ion{O}{3}], H$\alpha$, and the continuum are logarithmic, while the color scale for [\ion{Fe}{10}] is linear. Additionally, the fluxes have been convolved with a 5x5 median filter, and [\ion{Fe}{10}], [\ion{O}{3}], and H$\alpha$ have been masked such that only spaxels with an S/N~$ > 3$ are shown. The red ``$\times$'' displayed in each image denotes the positions for Nucleus 1 (northern source) and Nucleus 2 (southern source), respectively.
Figure 2: \textit{Top Left:} The [\ion{Fe}{10}] λ6374 emission line flux map. \textit{Top Right:} [\ion{O}{3}] λ5007 flux map. \textit{Bottom Left:} The Hα flux map. \textit{Bottom Right:} The continuum at λ5100 flux map. The red crosses in each image correspond to the positions of the peak continuum for the two brightest central clumps. Scale bars in kpc and arcseconds are given in the top left of each plot. The color scales for [\ion{O}{3}], Hα, and the continuum are logarithmic, while the color scale for [\ion{Fe}{10}] is linear. Additionally, the fluxes have been convolved with a 5x5 median filter, and [\ion{Fe}{10}], [\ion{O}{3}], and Hα have been masked such that only spaxels with an S/N~>3 are shown. The red ``×'' displayed in each image denotes the positions for Nucleus 1 (northern source) and Nucleus 2 (southern source), respectively.
\textit{Top Left:} The [\ion{Fe}{10}] $\lambda$6374 emission line flux map. \textit{Top Right:} [\ion{O}{3}] $\lambda$5007 flux map. \textit{Bottom Left:} The H$\alpha$ flux map. \textit{Bottom Right:} The continuum at $\lambda$5100  flux map. The red crosses in each image correspond to the positions of the peak continuum for the two brightest central clumps. Scale bars in kpc and arcseconds are given in the top left of each plot.  The color scales for [\ion{O}{3}], H$\alpha$, and the continuum are logarithmic, while the color scale for [\ion{Fe}{10}] is linear. Additionally, the fluxes have been convolved with a 5x5 median filter, and [\ion{Fe}{10}], [\ion{O}{3}], and H$\alpha$ have been masked such that only spaxels with an S/N~$ > 3$ are shown. The red ``$\times$'' displayed in each image denotes the positions for Nucleus 1 (northern source) and Nucleus 2 (southern source), respectively.
Figure 3: \textit{Top Left:} The [\ion{Fe}{10}] 6374 emission line flux map. \textit{Top Right:} [\ion{O}{3}] 5007 flux map. \textit{Bottom Left:} The H flux map. \textit{Bottom Right:} The continuum at 5100 flux map. The red crosses in each image correspond to the positions of the peak continuum for the two brightest central clumps. Scale bars in kpc and arcseconds are given in the top left of each plot. The color scales for [\ion{O}{3}], H, and the continuum are logarithmic, while the color scale for [\ion{Fe}{10}] is linear. Additionally, the fluxes have been convolved with a 5x5 median filter, and [\ion{Fe}{10}], [\ion{O}{3}], and H have been masked such that only spaxels with an S/N~ are shown. The red ``'' displayed in each image denotes the positions for Nucleus 1 (northern source) and Nucleus 2 (southern source), respectively.
\textit{Top Left:} The [\ion{Fe}{10}] $\lambda$6374 emission line flux map. \textit{Top Right:} [\ion{O}{3}] $\lambda$5007 flux map. \textit{Bottom Left:} The H$\alpha$ flux map. \textit{Bottom Right:} The continuum at $\lambda$5100  flux map. The red crosses in each image correspond to the positions of the peak continuum for the two brightest central clumps. Scale bars in kpc and arcseconds are given in the top left of each plot.  The color scales for [\ion{O}{3}], H$\alpha$, and the continuum are logarithmic, while the color scale for [\ion{Fe}{10}] is linear. Additionally, the fluxes have been convolved with a 5x5 median filter, and [\ion{Fe}{10}], [\ion{O}{3}], and H$\alpha$ have been masked such that only spaxels with an S/N~$ > 3$ are shown. The red ``$\times$'' displayed in each image denotes the positions for Nucleus 1 (northern source) and Nucleus 2 (southern source), respectively.
Figure 4: \textit{Top Left:} The [\ion{Fe}{10}] 6374 emission line flux map. \textit{Top Right:} [\ion{O}{3}] 5007 flux map. \textit{Bottom Left:} The H flux map. \textit{Bottom Right:} The continuum at 5100 flux map. The red crosses in each image correspond to the positions of the peak continuum for the two brightest central clumps. Scale bars in kpc and arcseconds are given in the top left of each plot. The color scales for [\ion{O}{3}], H, and the continuum are logarithmic, while the color scale for [\ion{Fe}{10}] is linear. Additionally, the fluxes have been convolved with a 5x5 median filter, and [\ion{Fe}{10}], [\ion{O}{3}], and H have been masked such that only spaxels with an S/N~ are shown. The red ``'' displayed in each image denotes the positions for Nucleus 1 (northern source) and Nucleus 2 (southern source), respectively.
\textit{Top Left:} The [\ion{Fe}{10}] $\lambda$6374 emission line flux map. \textit{Top Right:} [\ion{O}{3}] $\lambda$5007 flux map. \textit{Bottom Left:} The H$\alpha$ flux map. \textit{Bottom Right:} The continuum at $\lambda$5100  flux map. The red crosses in each image correspond to the positions of the peak continuum for the two brightest central clumps. Scale bars in kpc and arcseconds are given in the top left of each plot.  The color scales for [\ion{O}{3}], H$\alpha$, and the continuum are logarithmic, while the color scale for [\ion{Fe}{10}] is linear. Additionally, the fluxes have been convolved with a 5x5 median filter, and [\ion{Fe}{10}], [\ion{O}{3}], and H$\alpha$ have been masked such that only spaxels with an S/N~$ > 3$ are shown. The red ``$\times$'' displayed in each image denotes the positions for Nucleus 1 (northern source) and Nucleus 2 (southern source), respectively.
Figure 5: \textit{Top Left:} The [\ion{Fe}{10}] 6374 emission line flux map. \textit{Top Right:} [\ion{O}{3}] 5007 flux map. \textit{Bottom Left:} The H flux map. \textit{Bottom Right:} The continuum at 5100 flux map. The red crosses in each image correspond to the positions of the peak continuum for the two brightest central clumps. Scale bars in kpc and arcseconds are given in the top left of each plot. The color scales for [\ion{O}{3}], H, and the continuum are logarithmic, while the color scale for [\ion{Fe}{10}] is linear. Additionally, the fluxes have been convolved with a 5x5 median filter, and [\ion{Fe}{10}], [\ion{O}{3}], and H have been masked such that only spaxels with an S/N~ are shown. The red ``'' displayed in each image denotes the positions for Nucleus 1 (northern source) and Nucleus 2 (southern source), respectively.
\textit{Top Left:} The 1D extraction of the MUSE Spectrum from a $1\arcsec$ diameter circular aperture centered on Nucleus 1 (corresponding to the positions of the northern red ``$\times$'' in Figure~\ref{fig:musemaps}) showing the [\ion{Fe}{10}]\,$\lambda$6374 and H$\alpha$ region of the spectrum. The spectrum for Nucleus 1 was decomposed into broad and narrow components. A broad line was detected at the $>99.92~\%$ confidence level in Nucleus 1 with FWHM of $446 \pm 17$~km~s$^{-1}$.
Figure 6: \textit{Top Left:} The 1D extraction of the MUSE Spectrum from a diameter circular aperture centered on Nucleus 1 (corresponding to the positions of the northern red ``'' in Figure~) showing the [\ion{Fe}{10}]\,6374 and H region of the spectrum. The spectrum for Nucleus 1 was decomposed into broad and narrow components. A broad line was detected at the confidence level in Nucleus 1 with FWHM of ~km~s.
VLA X-band contours of the radio emission coincident with the [\ion{Fe}{10}] source, overlaid on a $2\arcsec\times2\arcsec$ cutout of the HST image from Figure~\ref{fig:mass}.The contours start at the 3$\sigma$ level (23.5~$\mu$Jy~beam$^{-1}$) and increase by integer multiples of the $\sqrt{2}$. The VLA image has an angular resolution of 0.2$^{\prime \prime}$.
Figure 7: VLA X-band contours of the radio emission coincident with the [\ion{Fe}{10}] source, overlaid on a cutout of the HST image from Figure~.The contours start at the 3 level (23.5~Jy~beam) and increase by integer multiples of the . The VLA image has an angular resolution of 0.2.
\textit{Left}: A BPT ratio plot of the CLASS sample with the values obtained from the $1~\arcsec$ aperture centered on Nucleus 1 and 2 displayed by the red diamonds. The color of each point corresponds to the stellar mass of the galaxy obtained from the MPA/JHU catalog. The star-forming, ``composite,'' and AGN regions are marked with text and separated by the curves defined in \citet{2003MNRAS.346.1055K} and \citet{2001ApJ...556..121K}. The grey shading displays the BPT values for the entire MPA/JHU catalog \\ \textit{Right}: A WISE color-color plot of the class sample with the value for J0944$-$0038 displayed by the red diamond. The coloring of the points and contours is defined the same way as the BPT plot. The AGN demarcation box from \citet{2011ApJ...735..112J} is shown by the black line, the demarcation box from \citet{2018ApJ...858...38S} is shown by the red line, and the demarcation box from \citet{2018MNRAS.478.3056B} is shown in green.
Figure 8: \textit{Left}: A BPT ratio plot of the CLASS sample with the values obtained from the aperture centered on Nucleus 1 and 2 displayed by the red diamonds. The color of each point corresponds to the stellar mass of the galaxy obtained from the MPA/JHU catalog. The star-forming, ``composite,'' and AGN regions are marked with text and separated by the curves defined in \citet{2003MNRAS.346.1055K} and \citet{2001ApJ...556..121K}. The grey shading displays the BPT values for the entire MPA/JHU catalog \textit{Right}: A WISE color-color plot of the class sample with the value for J09440038 displayed by the red diamond. The coloring of the points and contours is defined the same way as the BPT plot. The AGN demarcation box from \citet{2011ApJ...735..112J} is shown by the black line, the demarcation box from \citet{2018ApJ...858...38S} is shown by the red line, and the demarcation box from \citet{2018MNRAS.478.3056B} is shown in green.