More Like this

1. Unveiling the warm and dense ISM in z  > 6 quasar host galaxies via water vapor emission

   https://doi.org/10.1051/0004-6361/202243406  

   Pensabene, A. ; van der Werf, P. ; Decarli, R. ; Bañados, E. ; Meyer, R. A. ; Riechers, D. ; Venemans, B. ; Walter, F. ; Weiß, A. ; Brusa, M. ; et al ( November 2022 , Astronomy & Astrophysics)

   Water vapor (H₂O) is one of the brightest molecular emitters after carbon monoxide (CO) in galaxies with high infrared (IR) luminosity, allowing us to investigate the warm and dense phase of the interstellar medium (ISM) where star formation occurs. However, due to the complexity of its radiative spectrum, H₂O is not frequently exploited as an ISM tracer in distant galaxies. Therefore, H₂O studies of the warm and dense gas at high-zremain largely unexplored. In this work, we present observations conducted with the Northern Extended Millimeter Array (NOEMA) toward threez > 6 IR-bright quasarsJ2310+1855,J1148+5251, andJ0439+1634targeted in their multiple para- and ortho-H₂O transitions (3₁₂ − 3₀₃, 1₁₁ − 0₀₀, 2₂₀ − 2₁₁, and 4₂₂ − 4₁₃), as well as their far-IR (FIR) dust continuum. By combining our data with previous measurements from the literature, we estimated the dust masses and temperatures, continuum optical depths, IR luminosities, and star formation rates (SFR) from the FIR continuum. We modeled the H₂O lines using the MOLPOP-CEP radiative transfer code, finding that water vapor lines in our quasar host galaxies are primarily excited in the warm, dense (with a gas kinetic temperature and density ofT_kin = 50 K,n_H2 ∼ 10^4.5 − 10⁵ cm⁻³) molecular medium with a water vapor column density ofN_H2O ∼ 2 × 10¹⁷ − 3 × 10¹⁸ cm⁻³. High-JH₂O lines are mainly radiatively pumped by the intense optically-thin far-IR radiation field associated with a warm dust component at temperatures ofT_dust ∼ 80 − 190 K that account for < 5 − 10% of the total dust mass. In the case of J2310+1855, our analysis points to a relatively high value of the continuum optical depth at 100 μm (τ₁₀₀ ∼ 1). Our results are in agreement with expectations based on the H₂O spectral line energy distribution of local and high-zultra-luminous IR galaxies and active galactic nuclei (AGN). The analysis of the Boltzmann diagrams highlights the interplay between collisions and IR pumping in populating the high H₂O energy levels and it allows us to directly compare the excitation conditions in the targeted quasar host galaxies. In addition, the observations enable us to sample the high-luminosity part of the H₂O–total-IR (TIR) luminosity relations (L_H2O − L_TIR). Overall, our results point to supralinear trends that suggest H₂O–TIR relations are likely driven by IR pumping, rather than the mere co-spatiality between the FIR continuum- and line-emitting regions. The observedL_H2O/L_TIRratios in ourz > 6 quasars do not show any strong deviations with respect to those measured in star-forming galaxies and AGN at lower redshifts. This supports the notion that H₂O can be likely used to trace the star formation activity buried deep within the dense molecular clouds.

    

   more » « less
2. Physical Constraints on the Extended Interstellar Medium of the z = 6.42 Quasar J1148+5251: [C ii] 158 μm , [N ii] 205 μm , and [O i] 146 μm Observations

   https://doi.org/10.3847/1538-4357/ac4e94  

   Meyer, Romain A. ; Walter, Fabian ; Cicone, Claudia ; Cox, Pierre ; Decarli, Roberto ; Neri, Roberto ; Novak, Mladen ; Pensabene, Antonio ; Riechers, Dominik ; Weiss, Axel ( March 2022 , The Astrophysical Journal)

   Abstract We report new Northern Extended Millimeter Array observations of the [C ii ] 158 μ m , [N ii ] 205 μ m , and [O i ] 146 μ m atomic fine structure lines (FSLs) and dust continuum emission of J1148+5251, a z = 6.42 quasar, which probe the physical properties of its interstellar medium (ISM). The radially averaged [C ii ] 158 μ m and dust continuum emission have similar extensions (up to θ = 2.51 − 0.25 + 0.46 arcsec , corresponding to r = 9.8 − 2.1 + 3.3 kpc , accounting for beam convolution), confirming that J1148+5251 is the quasar with the largest [C ii ] 158 μ m -emitting reservoir known at these epochs. Moreover, if the [C ii ] 158 μ m emission is examined only along its NE–SW axis, a significant excess (>5.8 σ ) of [C ii ] 158 μ m emission (with respect to the dust) is detected. The new wide-bandwidth observations enable us to accurately constrain the continuum emission, and do not statistically require the presence of broad [C ii ] 158 μ m line wings that were reported in previous studies. We also report the first detection of the [O i ] 146 μ m and (tentatively) [N ii ] 205 μ m emission lines in J1148+5251. Using FSL ratios of the [C ii ] 158 μ m , [N ii ] 205 μ m , [O i ] 146 μ m , and previously measured [C i ] 369 μ m emission lines, we show that J1148+5251 has similar ISM conditions compared to lower-redshift (ultra)luminous infrared galaxies. CLOUDY modeling of the FSL ratios excludes X-ray-dominated regions and favors photodissociation regions as the origin of the FSL emission. We find that a high radiation field (10 3.5–4.5 G 0 ), a high gas density ( n ≃ 10 3.5–4.5 cm −3 ), and an H i column density of 10 23 cm −2 reproduce the observed FSL ratios well. 

   more » « less
3. Imaging the molecular interstellar medium in a gravitationally lensed star-forming galaxy at z = 5.7

   https://doi.org/10.1051/0004-6361/201935308  

   Apostolovski, Yordanka ; Aravena, Manuel ; Anguita, Timo ; Spilker, Justin ; Weiß, Axel ; Béthermin, Matthieu ; Chapman, Scott C. ; Chen, Chian-Chou ; Cunningham, Daniel ; De Breuck, Carlos ; et al ( August 2019 , Astronomy & Astrophysics)

   Aims . We present and study spatially resolved imaging obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) of multiple 12 CO( J  = 6 − 5, 8−7, and 9−8) and two H 2 O(2 02 −1 11 and 2 11 −2 02 ) emission lines and cold dust continuum toward the gravitationally lensed dusty star-forming galaxy SPT 0346-52 at z  = 5.656. Methods . Using a visibility-domain source-plane reconstruction we probe the structure and dynamics of the different components of the interstellar medium (ISM) in this galaxy down to scales of 1 kpc in the source plane. Results . Measurements of the intrinsic sizes of the different CO emission lines indicate that the higher J transitions trace more compact regions in the galaxy. Similarly, we find smaller dust continuum intrinsic sizes with decreasing wavelength, based on observations at rest frame 130, 300, and 450 μ m. The source shows significant velocity structure, and clear asymmetry where an elongated structure is observed in the source plane with significant variations in their reconstructed sizes. This could be attributed to a compact merger or turbulent disk rotation. The differences in velocity structure through the different line tracers, however, hint at the former scenario in agreement with previous [CII] line imaging results. Measurements of the CO line ratios and magnifications yield significant variations as a function of velocity, suggesting that modeling of the ISM using integrated values could be misinterpreted. Modeling of the ISM in SPT 0346-52 based on delensed fluxes indicates a highly dense and warm medium, qualitatively similar to that observed in high-redshift quasar hosts. 

   more » « less
4. The Rest-frame Submillimeter Spectrum of High-redshift, Dusty, Star-forming Galaxies from the SPT-SZ Survey

   https://doi.org/10.3847/1538-4357/acaf51  

   Reuter, C. ; Spilker, J. S. ; Vieira, J. D. ; Marrone, D. P. ; Weiss, A. ; Aravena, M. ; Archipley, M. A. ; Chapman, S. C. ; Gonzalez, A. ; Greve, T. R. ; et al ( May 2023 , The Astrophysical Journal)

   We present the average rest-frame spectrum of the final catalog of dusty star-forming galaxies (DSFGs) selected from the South Pole Telescope's SPT-SZ survey and measured with Band 3 of the Atacama Large Millimeter/submillimeter Array. This work builds on the previous average rest-frame spectrum, given in Spilker et al. (2014) for the first 22 sources, and is comprised of a total of 78 sources, normalized by their respective apparent dust masses. The spectrum spans 1.9 <z< 6.9 and covers rest-frame frequencies of 240–800 GHz. Combining this data with low-JCO observations from the Australia Telescope Compact Array, we detect multiple bright line features from¹²CO, [Ci], and H₂O, as well as fainter molecular transitions from¹³CO, HCN, HCO⁺, HNC, CN, H₂O⁺, and CH. We use these detections, along with limits from other molecules, to characterize the typical properties of the interstellar medium (ISM) for these high-redshift DSFGs. We are able to divide the large sample into subsets in order to explore how the average spectrum changes with various galaxy properties, such as effective dust temperature. We find that systems with hotter dust temperatures exhibit differences in the bright¹²CO emission lines, and contain either warmer and more excited dense gas tracers or larger dense gas reservoirs. These observations will serve as a reference point to studies of the ISM in distant luminous DSFGs (L_IR> 10¹²L_⊙), and will inform studies of chemical evolution before the peak epoch of star formation atz= 2–3.

    

   more » « less
5. Molecular gas in AzTEC/C159: a star-forming disk galaxy 1.3Gyr after the Big Bang

   Jiménez-Andrade, E. F. ; Magnelli, B. ; Karim, A. ; Jones, G. C. ; Carilli, C. L. ; Romano-Díaz, E. ; Gómez-Guijarro, C. ; Toft, S. ; Bertoldi, F. ; Riechers, D. A. ; et al ( January 2018 , Astronomy & astrophysics)

   We studied the molecular gas properties of AzTEC/C159, a star-forming disk galaxy at $z=4.567$. We secured $^{12}$CO molecular line detections for the $J=2\to1$ and $J=5\to4$ transitions using the Karl G. Jansky VLA and the NOEMA interferometer. The broad (FWHM$\sim750\,{\rm km\,s}^{-1}$) and tentative double-peaked profiles of both $^{12}$CO lines are consistent with an extended molecular gas reservoir, which is distributed in a rotating disk as previously revealed from [CII] 158$\mu$m line observations. Based on the $^{12}$CO(2$\to$1) emission line we derived $L'_{\rm{CO}}=(3.4\pm0.6)\times10^{10}{\rm \,K\,km\,s}^{-1}{\rm \,pc}^{2}$, that yields a molecular gas mass of $M_{\rm H_2 }(\alpha_{\rm CO}/4.3)=(1.5\pm0.3)\times 10^{11}{\rm M}_\odot$ and unveils a gas-rich system with $\mu_{\rm gas}(\alpha_{\rm CO}/4.3)\equiv M_{\rm H_2}/M_\star=3.3\pm0.7$. The extreme star formation efficiency (SFE) of AzTEC/C159, parametrized by the ratio $L_{\rm{IR}}/L'_{\rm{CO}}=(216\pm80)\, {\rm L}_{\odot}{\rm \,(K\,km\,s}^{-1}{\rm \,pc}^{2})^{-1}$, is comparable to merger-driven starbursts such as local ultra-luminous infrared galaxies (ULIRGs) and SMGs. Likewise, the $^{12}$CO(5$\to$4)/CO(2$\to$1) line brightness temperature ratio of $r_{52}= 0.55\pm 0.15$ is consistent with high excitation conditions, similar to that observed in SMGs. We constrained the value for the $L'_{\text{CO}}-{\rm H}_2$ mass conversion factor in AzTEC/C159, i.e. $\alpha_{\text{CO}}=3.9^{+2.7}_{-1.3}{\rm \,M}_{\odot}{\rm \,K}^{-1}{\rm \,km}^{-1}{\rm \,s\,pc}^{-2}$, that is consistent with a self-gravitating molecular gas distribution as observed in local star-forming disk galaxies. Cold gas streams from cosmological filaments might be fueling a gravitationally unstable gas-rich disk in AzTEC/C159, which breaks into giant clumps forming stars as efficiently as in merger-driven systems and generate high gas excitation. 

   more » « less