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1. The ALPINE-ALMA [C  ii ] survey: Investigation of 10 galaxies at z ∼ 4.5 with [O  ii ] and [C  ii ] line emission − ISM properties and [O  ii ]−SFR relation

   https://doi.org/10.1093/mnras/stac071  

   Vanderhoof, Brittany N. ; Faisst, A. L. ; Shen, L. ; Lemaux, B. C. ; Béthermin, M. ; Capak, P. L. ; Cassata, P. ; Le Fèvre, O. ; Schaerer, D. ; Silverman, J. ; et al ( January 2022 , Monthly Notices of the Royal Astronomical Society)

   We present 10 main-sequence ALPINE galaxies (log (M/M⊙) = 9.2−11.1 and ${\rm SFR}=23-190\, {\rm M_{\odot }\, yr^{-1}}$) at z ∼ 4.5 with optical [O ii] measurements from Keck/MOSFIRE spectroscopy and Subaru/MOIRCS narrow-band imaging. This is the largest such multiwavelength sample at these redshifts, combining various measurements in the ultraviolet, optical, and far-infrared including [C ii]158 $\mu$m line emission and dust continuum from ALMA and H α emission from Spitzer photometry. For the first time, this unique sample allows us to analyse the relation between [O ii] and total star-formation rate (SFR) and the interstellar medium (ISM) properties via [O ii]/[C ii] and [O ii]/H α luminosity ratios at z ∼ 4.5. The [O ii]−SFR relation at z ∼ 4.5 cannot be described using standard local descriptions, but is consistent with a metal-dependent relation assuming metallicities around $50{{\ \rm per\ cent}}$ solar. To explain the measured dust-corrected luminosity ratios of $\log (L_{\rm [OII]}/L_{\rm [CII]}) \sim 0.98^{+0.21}_{-0.22}$ and $\log (L_{\rm [OII]}/L_{\rm H\alpha }) \sim -0.22^{+0.13}_{-0.15}$ for our sample, ionization parameters log (U) < −2 and electron densities $\log (\rm n_e / {\rm [cm^{-3}]}) \sim 2.5-3$ are required. The former is consistent with galaxies at z ∼ 2−3, however lower than at z > 6. The latter may be slightly higher than expected given the galaxies’ specific SFR. Themore »analysis of this pilot sample suggests that typical log (M/M⊙) > 9 galaxies at z ∼ 4.5 to have broadly similar ISM properties as their descendants at z ∼ 2 and suggest a strong evolution of ISM properties since the epoch of reionization at z > 6.

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2. SÍGAME Simulations of the [{ m{C}},{ m{II}}], [{ m{O}},{ m{I}}], and [{ m{O}},{ m{III}}] Line Emission from Star-forming Galaxies at zsimeq 6

   Olsen, Karen ; Greve, Thomas R. ; Narayanan, Desika ; Thompson, Robert ; Davé, Romeel ; Niebla Rios, Luis ; Stawinski, Stephanie ( January 2017 , Astrophysical journal)

   Of the almost 40 star-forming galaxies at z≳ 5 (not counting quasi-stellar objects) observed in [{{C}} {{II}}] to date, nearly half are either very faint in [{{C}} {{II}}] or not detected at all, and fall well below expectations based on locally derived relations between star formation rate and [{{C}} {{II}}] luminosity. This has raised questions as to how reliable [{{C}} {{II}}] is as a tracer of star formation activity at these epochs and how factors such as metallicity might affect the [{{C}} {{II}}] emission. Combining cosmological zoom simulations of galaxies with SÍGAME (SImulator of GAlaxy Millimeter/submillimeter Emission), we modeled the multiphased interstellar medium (ISM) and its emission in [{{C}} {{II}}], as well as in [O I] and [O III], from 30 main-sequence galaxies at z≃ 6 with star formation rates ˜3-23 {M}⊙ {yr}}-1, stellar masses ˜ (0.7{--}8)× {10}9 {M}⊙ , and metallicities ˜ (0.1{--}0.4)× {Z}⊙ . The simulations are able to reproduce the aforementioned [{{C}} {{II}}] faintness of some normal star-forming galaxy sources at z≥slant 5. In terms of [O I] and [O III], very few observations are available at z≳ 5, but our simulations match two of the three existing z≳ 5 detections of [O III] and are furthermoremore »roughly consistent with the [O I] and [O III] luminosity relations with star formation rate observed for local starburst galaxies. We find that the [{{C}} {{II}}] emission is dominated by the diffuse ionized gas phase and molecular clouds, which on average contribute ˜66% and ˜27%, respectively. The molecular gas, which constitutes only ˜ 10 % of the total gas mass, is thus a more efficient emitter of [{{C}} {{II}}] than the ionized gas, which makes up ˜85% of the total gas mass. A principal component analysis shows that the [{{C}} {{II}}] luminosity correlates with the star formation activity of a galaxy as well as its average metallicity. The low metallicities of our simulations together with their low molecular gas mass fractions can account for their [{{C}} {{II}}] faintness, and we suggest that these factors may also be responsible for the [{{C}} {{II}}]-faint normal galaxies observed at these early epochs.« less
3. The MOSDEF survey: the mass–metallicity relationship and the existence of the FMR at z ∼ 1.5

   https://doi.org/10.1093/mnras/stab1793  

   Topping, Michael W ; Shapley, Alice E ; Sanders, Ryan L ; Kriek, Mariska ; Reddy, Naveen A ; Coil, Alison L ; Mobasher, Bahram ; Siana, Brian ; Freeman, William R ; Shivaei, Irene ; et al ( July 2021 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We analyse the rest-optical emission-line ratios of z ∼ 1.5 galaxies drawn from the Multi-Object Spectrometer for Infra-Red Exploration Deep Evolution Field (MOSDEF) survey. Using composite spectra, we investigate the mass–metallicity relation (MZR) at z ∼ 1.5 and measure its evolution to z = 0. When using gas-phase metallicities based on the N2 line ratio, we find that the MZR evolution from z ∼ 1.5 to z = 0 depends on stellar mass, evolving by $\Delta \rm log(\rm O/H) \sim 0.25$ dex at M*< $10^{9.75}\, \mathrm{M}_{\odot }$ down to $\Delta \rm log(\rm O/H) \sim 0.05$ at M* ≳ $10^{10.5}\, \mathrm{M}_{\odot }$. In contrast, the O3N2-based MZR shows a constant offset of $\Delta \rm log(\rm O/H) \sim 0.30$ across all masses, consistent with previous MOSDEF results based on independent metallicity indicators, and suggesting that O3N2 provides a more robust metallicity calibration for our z ∼ 1.5 sample. We investigated the secondary dependence of the MZR on star formation rate (SFR) by measuring correlated scatter about the mean M*-specific SFR and M*−$\log (\rm O3N2)$ relations. We find an anticorrelation between $\log (\rm O/H)$ and sSFR offsets, indicating the presence of a M*−SFR−Z relation, though with limited significance. Additionally, we find that our z ∼ 1.5more »stacks lie along the z = 0 metallicity sequence at fixed μ = log (M*/M⊙) − 0.6 × $\log (\rm SFR / M_{\odot } \, yr^{-1})$ suggesting that the z ∼ 1.5 stacks can be described by the z = 0 fundamental metallicity relation (FMR). However, using different calibrations can shift the calculated metallicities off of the local FMR, indicating that appropriate calibrations are essential for understanding metallicity evolution with redshift. Finally, understanding how [N ii]/H α scales with galaxy properties is crucial to accurately describe the effects of blended [N ii] and H α on redshift and H α fiux measurements in future large surveys utilizing low-resolution spectra such as with Euclid and the Roman Space Telescope.« less
4. Close-up view of a luminous star-forming galaxy at z = 2.95

   https://doi.org/10.1051/0004-6361/202039743  

   Berta, S. ; Young, A. J. ; Cox, P. ; Neri, R. ; Jones, B. M. ; Baker, A. J. ; Omont, A. ; Dunne, L. ; Carnero Rosell, A. ; Marchetti, L. ; et al ( February 2021 , Astronomy & Astrophysics)

   Exploiting the sensitivity of the IRAM NOrthern Extended Millimeter Array (NOEMA) and its ability to process large instantaneous bandwidths, we have studied the morphology and other properties of the molecular gas and dust in the star forming galaxy, H-ATLAS J131611.5+281219 (HerBS-89a), at z = 2.95. High angular resolution (0 . ″3) images reveal a partial 1 . ″0 diameter Einstein ring in the dust continuum emission and the molecular emission lines of 12 CO(9−8) and H 2 O(2 02  − 1 11 ). Together with lower angular resolution (0 . ″6) images, we report the detection of a series of molecular lines including the three fundamental transitions of the molecular ion OH + , namely (1 1  − 0 1 ), (1 2  − 0 1 ), and (1 0  − 0 1 ), seen in absorption; the molecular ion CH + (1 − 0) seen in absorption, and tentatively in emission; two transitions of amidogen (NH 2 ), namely (2 02  − 1 11 ) and (2 20  − 2 11 ) seen in emission; and HCN(11 − 10) and/or NH(1 2  − 0 1 ) seen in absorption. The NOEMA data are complemented with Very Large Array data tracing the 12 CO(1 − 0) emission line, which provides a measurement ofmore »the total mass of molecular gas and an anchor for a CO excitation analysis. In addition, we present Hubble Space Telescope imaging that reveals the foreground lensing galaxy in the near-infrared (1.15  μ m). Together with photometric data from the Gran Telescopio Canarias, we derive a photometric redshift of z phot = 0.9 −0.5 +0.3 for the foreground lensing galaxy. Modeling the lensing of HerBS-89a, we reconstruct the dust continuum (magnified by a factor μ  ≃ 5.0) and molecular emission lines (magnified by μ  ∼ 4 − 5) in the source plane, which probe scales of ∼0 . ″1 (or 800 pc). The 12 CO(9 − 8) and H 2 O(2 02  − 1 11 ) emission lines have comparable spatial and kinematic distributions; the source-plane reconstructions do not clearly distinguish between a one-component and a two-component scenario, but the latter, which reveals two compact rotating components with sizes of ≈1 kpc that are likely merging, more naturally accounts for the broad line widths observed in HerBS-89a. In the core of HerBS-89a, very dense gas with n H 2  ∼ 10 7 − 9 cm −3 is revealed by the NH 2 emission lines and the possible HCN(11 − 10) absorption line. HerBS-89a is a powerful star forming galaxy with a molecular gas mass of M mol  = (2.1 ± 0.4) × 10 11   M ⊙ , an infrared luminosity of L IR  = (4.6 ± 0.4) × 10 12   L ⊙ , and a dust mass of M dust  = (2.6 ± 0.2) × 10 9   M ⊙ , yielding a dust-to-gas ratio δ GDR  ≈ 80. We derive a star formation rate SFR = 614 ± 59  M ⊙ yr −1 and a depletion timescale τ depl  = (3.4 ± 1.0) × 10 8 years. The OH + and CH + absorption lines, which trace low (∼100 cm −3 ) density molecular gas, all have their main velocity component red-shifted by Δ V  ∼ 100 km s −1 relative to the global CO reservoir. We argue that these absorption lines trace a rare example of gas inflow toward the center of a galaxy, indicating that HerBS-89a is accreting gas from its surroundings.« less
5. The Close AGN Reference Survey (CARS): IFU survey data and the BH mass dependence of long-term AGN variability

   https://doi.org/10.1051/0004-6361/202141312  

   Husemann, B. ; Singha, M. ; Scharwächter, J. ; McElroy, R. ; Neumann, J. ; Smirnova-Pinchukova, I. ; Urrutia, T. ; Baum, S. A. ; Bennert, V. N. ; Combes, F. ; et al ( March 2022 , Astronomy & Astrophysics)

   Context. Active galactic nuclei (AGN) are thought to be intimately connected with their host galaxies through feeding and feedback processes. A strong coupling is predicted and supported by cosmological simulations of galaxy formation, but the details of the physical mechanisms are still observationally unconstrained. Aims. Galaxies are complex systems of stars and a multiphase interstellar medium (ISM). A spatially resolved multiwavelength survey is required to map the interaction of AGN with their host galaxies on different spatial scales and different phases of the ISM. The goal of the Close AGN Reference Survey (CARS) is to obtain the necessary spatially resolved multiwavelength observations for an unbiased sample of local unobscured luminous AGN. Methods. We present the overall CARS survey design and the associated wide-field optical integral-field unit (IFU) spectroscopy for all 41 CARS targets at z  < 0.06 randomly selected from the Hamburg/ESO survey of luminous unobscured AGN. This data set provides the backbone of the CARS survey and allows us to characterize host galaxy morphologies, AGN parameters, precise systemic redshifts, and ionized gas distributions including excitation conditions, kinematics, and metallicities in unprecedented detail. Results. We focus our study on the size of the extended narrow-line region (ENLR) which has been traditionallymore »connected to AGN luminosity. Given the large scatter in the ENLR size–luminosity relation, we performed a large parameter search to identify potentially more fundamental relations. Remarkably, we identified the strongest correlation between the maximum projected ENLR size and the black hole mass, consistent with an R ENLR,max ∼ M BH 0.5 relationship. We interpret the maximum ENLR size as a timescale indicator of a single black hole (BH) radiative-efficient accretion episode for which we inferred 〈log( t AGN /[yr])〉 = (0.45 ± 0.08)log( M BH /[ M ⊙ ]) + 1.78 −0.67 +0.54 using forward modeling. The extrapolation of our inferred relation toward higher BH masses is consistent with an independent lifetime estimate from the He  II proximity zones around luminous AGN at z  ∼ 3. Conclusions. While our proposed link between the BH mass and AGN lifetime might be a secondary correlation itself or impacted by unknown biases, it has a few relevant implications if confirmed. For example, the famous AGN Eigenvector 1 parameter space may be partially explained by the range in AGN lifetimes. Also, the lack of observational evidence for negative AGN feedback on star formation can be explained by such timescale effects. Further observational tests are required to confirm or rule out our BH mass dependent AGN lifetime hypothesis.« less