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  • 1. Behrens, C.
    et al.
    Pallottini, A.
    Ferrara, A.
    Gallerani, S.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Dusty galaxies in the Epoch of Reionization: simulations2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 477, no 1, p. 552-565Article in journal (Refereed)
    Abstract [en]

    The recent discovery of dusty galaxies well into the Epoch of Reionization (redshift z > 6) poses challenging questions about the properties of the interstellar medium in these pristine systems. By combining state-of-the-art hydrodynamic and dust radiative transfer simulations, we address these questions focusing on the recently discovered dusty galaxy A2744_YD4 (z = 8.38, Laporte et al.). We show that we can reproduce the observed spectral energy distribution (SED) only using different physical values with respect to the inferred ones by Laporte et al., i.e. a star formation rate of SFR = 78 M(circle dot)yr(-1), a factor approximate to 4 higher than deduced from simple SED fitting. In this case, we find: (i) dust attenuation (corresponding to tau(v) = 1.4) is consistent with a Milky Way (MW) extinction curve; (ii) the dust-to-metal ratio is low, f(d) similar to 0.08, implying that early dust formation is rather inefficient;(iii) the luminosity-weighted dust temperature is high, T-d = 91 23 K, as a result of the intense (approximate to 100 x MW) interstellar radiation field; and (iv) due to the high T-d, the Atacama Large Millimeter/submillimeter Array Band 7 detection can be explained by a limited dust mass, M-d = 1.6 x 10(6) M-circle dot. Finally, the high dust temperatures might solve the puzzling low infrared excess (IRX) recently deduced for high-z galaxies from the IRX-beta relation.

  • 2. Behrens, C.
    et al.
    Pallottini, A.
    Ferrara, A.
    Gallerani, S.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Leiden University, the Netherlands.
    Ly alpha emission from galaxies in the Epoch of eionization2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 486, no 2, p. 2197-2209Article in journal (Refereed)
    Abstract [en]

    The intrinsic strength of the Ly alpha line in young, star-forming systems makes it a special tool for studying high-redshift galaxies. However, interpreting observations remains challenging due to the complex radiative transfer involved. Here, we combine state-of-the-art hydrodynamical simulations of 'Althaea', a prototypical Lyman Break Galaxy (LBG; stellar mass M-star similar or equal to 10(10) M-circle dot) at z = 7.2, with detailed radiative transfer computations of dust/continuum, [C II] 158 mu m, and Ly alpha to clarify the relation between the galaxy properties and its Ly alpha emission. Althaea exhibits low (f(alpha) < 1 per cent) Ly alpha escape fractions and equivalent widths, EW less than or similar to 6 angstrom for the simulated lines of sight, with a large scatter. The correlation between escape fraction and inclination is weak, as a result of the rather chaotic structure of high-redshift galaxies. Low f(alpha) values persist even if we artificially remove neutral gas around star-forming regions to mimic the presence of H II regions. The high attenuation is primarily caused by dust clumps co-located with young stellar clusters. We can turn Althaea into a Lyman Alpha Emitter (LAE) only if we artificially remove dust from the clumps, yielding EWs up to 22 angstrom. Our study suggests that the LBG-LAE duty-cycle required by recent clustering measurements poses the challenging problem of a dynamically changing dust attenuation. Finally, we find an anticorrelation between the magnitude of Ly alpha-[C II] line velocity shift and Ly alpha luminosity.

  • 3. Bradac, Marusa
    et al.
    Garcia-Appadoo, Diego
    Huang, Kuang-Han
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Dipartimento di Fisica e Astronomia, Bologna, Italy; INAF, Osservatorio Astronomico di Bologna, Italy.
    Finney, Emily Quinn
    Hoag, Austin
    Lemaux, Brian C.
    Schmidt, Kasper Borello
    Treu, Tommaso
    Carilli, Chris
    Dijkstra, Mark
    Ferrara, Andrea
    Fontana, Adriano
    Jones, Tucker
    Ryan, Russell
    Wagg, Jeff
    Gonzalez, Anthony H.
    ALMA [C II] 158 mu m Detection of a Redshift 7 Lensed Galaxy behind RXJ1347.1-11452017In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 836, no 1, article id L2Article in journal (Refereed)
    Abstract [en]

    We present the results of ALMA spectroscopic follow-up of a z = 6.766 Ly alpha emitting galaxy behind the cluster RX J1347.1-1145. We report the detection of [C II] 158 mu m line fully consistent with the Ly alpha redshift and with the peak of the optical emission. Given the magnification of mu = 5.0 +/- 0.3, the intrinsic (corrected for lensing) luminosity of the [C II] line is L[C II]= 1.4(-0.3)(+0.3) x 10(7) L-circle dot, roughly similar to 5 times fainter than other detections of z similar to 7 galaxies. The result indicates that low L[C II] in z similar to 7 galaxies compared to the local counterparts might be caused by their low metallicities and/or feedback. The small velocity offset (Delta v = 20(-40)(+40) km s(-1)) between the Ly alpha and [C II] line is unusual, and may be indicative of ionizing photons escaping.

  • 4. Carniani, S.
    et al.
    Gallerani, S.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Leiden Observatory, The Netherlands.
    Pallottini, A.
    Tazzari, M.
    Ferrara, A.
    Maiolino, R.
    Cicone, C.
    Feruglio, C.
    Neri, R.
    D'Odorico, V.
    Wang, R.
    Li, J.
    Constraints on high-J CO emission lines in z similar to 6 quasars2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 489, no 3, p. 3939-3952Article in journal (Refereed)
    Abstract [en]

    We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of eight highly excited CO (J(up) > 8) lines and continuum emission in two z similar to 6 quasars: SDSS J231038.88+185519.7 (hereafter J2310), for which CO(8-7), CO(9-8), and CO(17-16) lines have been observed, and ULAS J131911.29+095951.4 (J1319), observed in the CO(14-13), CO(17-16), and CO(19-18) lines. The continuum emission of both quasars arises from a compact region (<0.9 kpc). By assuming a modified blackbody law, we estimate dust masses of log(M-dust/M-circle dot) = 8.75 +/- 0.07 and log(M-dust/M-circle dot) = 8.8 +/- 0.2 and dust temperatures of T-dust = 76 +/- 3 K and T-dust = 66(-10)(+15) K, respectively, for J2310 and J1319. Only CO(8-7) and CO(9-8) in J2310 are detected, while 3 sigma upper limits on luminosities are reported for the other lines of both quasars. The CO line luminosities and upper limits measured in J2310 and J1319 are consistent with those observed in local active galactic nuclei and starburst galaxies, and other z similar to 6 quasars, except for SDSS J1148+5251 (J1148), the only quasar at z = 6.4 with a previous CO(17-16) line detection. By computing the CO spectral line energy distributions normalized to the CO(6-5) line and far-infrared luminosities for J2310, J1319, and J1148, we conclude that different gas heating mechanisms (X-ray radiation and/or shocks) may explain the different CO luminosities observed in these z similar to 6 quasar. Future J(up) > 8 CO observations will be crucial to understand the processes responsible for molecular gas excitation in luminous high-z quasars.

  • 5. Carniani, S.
    et al.
    Maiolino, R.
    Pallottini, A.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Pentericci, L.
    Ferrara, A.
    Castellano, M.
    Vanzella, E.
    Grazian, A.
    Gallerani, S.
    Santini, P.
    Wagg, J.
    Fontana, A.
    Extended ionised and clumpy gas in a normal galaxy at z=7.1 revealed by ALMA2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 605, article id A42Article in journal (Refereed)
    Abstract [en]

    We present new ALMA observations of the [O III] 88 mu m line and high angular resolution observations of the [C II] 158 mu m line in a normal star forming galaxy at z = 7.1. Previous [C II] observations of this galaxy had detected [C II] emission consistent with the Ly alpha redshift but spatially slightly off set relative to the optical (UV-rest frame) emission. The new [C II] observations reveal that the [C II] emission is partly clumpy and partly diffuse on scales larger than about 1 kpc. [O III] emission is also detected at high significance, off set relative to the optical counterpart in the same direction as the [C II] clumps, but mostly not overlapping with the bulk of the [C II] emission. The off set between different emission components (optical/UV and different far-IR tracers) is similar to that which is observed in much more powerful starbursts at high redshift. We show that the [O III] emitting clump cannot be explained in terms of diffuse gas excited by the UV radiation emitted by the optical galaxy, but it requires excitation by in-situ (slightly dust obscured) star formation, at a rate of about 7 M circle dot yr(-1). Within 20 kpc from the optical galaxy the ALMA data reveal two additional [O III] emitting systems, which must be star forming companions. We discuss that the complex properties revealed by ALMA in the z similar to 7.1 galaxy are consistent with expectations by recent models and cosmological simulations, in which differential dust extinction, differential excitation and different metal enrichment levels, associated with different subsystems assembling a galaxy, are responsible for the various appearance of the system when observed with distinct tracers.

  • 6. Citro, Annalisa
    et al.
    Pozzetti, Lucia
    Quai, Salvatore
    Moresco, Michele
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Università di Bologna, Italy; INAF-Osservatorio Astronomico di Bologna, Italy.
    Cimatti, Andrea
    A methodology to select galaxies just after the quenching of star formation2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, no 3, p. 3108-3124Article in journal (Refereed)
    Abstract [en]

    We propose a new methodology aimed at finding star-forming galaxies in the phase which immediately follows the star-formation (SF) quenching, based on the use of high-to low-ionization emission line ratios. These ratios rapidly disappear after the SF halt, due to the softening of the UV ionizing radiation. We focus on [O III]lambda 5007/H alpha and [Ne III]lambda 3869/[O II]lambda 3727, studying them with simulations obtained with the CLOUDY photoionization code. If a sharp quenching is assumed, we find that the two ratios are very sensitive tracers as they drop by a factor of similar to 10 within similar to 10 Myr from the interruption of the SF; instead, if a smoother and slower SF decline is assumed (i.e. an exponentially declining SF history with e-folding time tau = 200 Myr), they decrease by a factor of similar to 2 within similar to 80 Myr. We mitigate the ionization-metallicity degeneracy affecting our methodology using pairs of emission line ratios separately related to metallicity and ionization, adopting the [N II]lambda 6584/[OII]lambda 3727 ratio as metallicity diagnostic. Using a Sloan Digital Sky Survey galaxy sample, we identify 10 examples among the most extreme quenching candidates within the [O III]lambda 5007/H alpha versus [N II]lambda 6584/[O II]lambda 3727 plane, characterized by low [O III]lambda 5007/H alpha, faint [Ne III]lambda 3869, and by blue dust-corrected spectra and (u - r) colours, as expected if the SF quenching has occurred in the very recent past. Our results also suggest that the observed fractions of quenching candidates can be used to constrain the quenching mechanism at work and its time-scales.

  • 7. Decataldo, D.
    et al.
    Ferrara, A.
    Pallottini, Andrea
    Gallerani, S.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Molecular clumps photoevaporation in ionized regions2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 471, no 4, p. 4476-4487Article in journal (Refereed)
    Abstract [en]

    We study the photoevaporation of molecular clumps exposed to a UV radiation field including hydrogen-ionizing photons (h nu > 13.6 eV) produced by massive stars or quasars. We follow the propagation and collision of shockwaves inside clumps and take into account self-shielding effects, determining the evolution of clump size and density with time. The structure of the ionization-photodissociation region is obtained for different initial clump masses (M = 0.01- 10(4)M(circle dot)) and impinging fluxes (G(0) = 10(2)-10(5) in units of the Habing flux). The cases of molecular clumps engulfed in the HII region of an OB star and clumps carried within quasar outflows are treated separately. We find that the clump undergoes in both cases an initial shock-contraction phase and a following expansion phase, which lets the radiation penetrate in until the clump is completely evaporated. Typical evaporation time-scales are similar or equal to 0.01 Myr in the stellar case and 0.1 Myr in the quasar case, where the clump mass is 0.1 M-circle dot and 10(3)M(circle dot) , respectively. We find that clump lifetimes in quasar outflows are compatible with their observed extension, suggesting that photoevaporation is the main mechanism regulating the size of molecular outflows.

  • 8. Decataldo, D.
    et al.
    Pallottini, A.
    Ferrara, A.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Leiden University, the Netherlands.
    Gallerani, S.
    Photoevaporation of Jeans-unstable molecular clumps2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 487, no 3, p. 3377-3391Article in journal (Refereed)
    Abstract [en]

    We study the photoevaporation of Jeans-unstable molecular clumps by isotropic FUV (6 eV < by < 13.6 eV) radiation, through 3D radiative transfer hydrodynamical simulations implementing a non-equilibrium chemical network that includes the formation and dissociation of H2. We run a set of simulations considering different clump masses (M = 10-200 Mo) and impinging fluxes (G0 = 2 x 103 to 8 x 104 in Habing units). In the initial phase, the radiation sweeps the clump as an R-type dissociation front, reducing the H2 mass by a factor 40-90 per cent. Then, a weak (.A4 2) shock develops and travels towards the centre of the clump, which collapses while losing mass from its surface, All considered clumps remain gravitationally unstable even if radiation rips off most of the clump mass, showing that external REV radiation is not able to stop clump collapse. However, the REV intensity regulates the final H2 mass available for star formation: for example, for Go < 104 more than 10 per cent of the initial clump mass survives, Finally, for massive clumps (?, 100 the H2 mass increases by 25-50 per cent during the collapse, mostly because of the rapid density growth that implies a more efficient H2 self-shielding.

  • 9. Ferrara, A.
    et al.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Leiden University, the Netherlands.
    Pallottini, A.
    Gallerani, S.
    Carniani, S.
    Kohandel, M.
    Decataldo, D.
    Behrens, C.
    A physical model for [C II] line emission from galaxies2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 489, no 1, p. 1-12Article in journal (Refereed)
    Abstract [en]

    A tight relation between the [C II] 158 mu m line luminosity and star formation rate is measured in local galaxies. At high redshift (z > 5), though, a much larger scatter is observed, with a considerable (15-20 per cent) fraction of the outliers being [C II]-deficient. Moreover, the [C II] surface brightness (Sigma([C II])) of these sources is systematically lower than expected from the local relation. To clarify the origin of such [C II]-deficiency, we have developed an analytical model that fits local [C II] data and has been validated against radiative transfer simulations performed with CLOUDY. The model predicts an overall increase of Sigma([C II]) with Sigma(SFR). However, for Sigma(SFR) greater than or similar to 1M(circle dot) yr(-1) kpc(-2), Sigma([C II]) saturates. We conclude that underluminous [C II] systems can result from a combination of three factors: (a) large upward deviations from theKennicutt-Schmidt relation (kappa(s) >> 1), parametrized by the 'burstiness' parameter kappa(s); (b) low metallicity; (c) low gas density, at least for the most extreme sources (e.g. CR7). Observations of [C II] emission alone cannot break the degeneracy among the above three parameters; this requires additional information coming from other emission lines (e.g. [OIII]88 mu m, C III]1909 degrees, CO lines). Simple formulae are given to interpret available data for low- and high- z galaxies.

  • 10. Gallerani, S.
    et al.
    Pallottini, A.
    Feruglio, C.
    Ferrara, A.
    Maiolino, R.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Osservatorio Astronomico di Bologna, Italy; Università di Bologna, Italy.
    Riechers, D. A.
    Pavesi, R.
    ALMA suggests outflows in z similar to 5.5 galaxies2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 2, p. 1909-1917Article in journal (Refereed)
    Abstract [en]

    We present the first attempt to detect outflows from galaxies approaching the Epoch of Reionization (EoR) using a sample of nine star-forming (SFR = 31 +/- 20M(circle dot) yr(-1)) z similar to 5.5 galaxies for which the [C II] 158 mu m line has been previously obtained with Atacama Large Millimeter Array (ALMA). We first fit each line with a Gaussian function and compute the residuals by subtracting the best-fitting model from the data. We combine the residuals of all sample galaxies and find that the total signal is characterized by a flux excess of similar to 0.5 mJy extended over similar to 1000 km s(-1). Although we cannot exclude that part of this signal is due to emission from faint satellite galaxies, we show that the most probable explanation for the detected flux excess is the presence of broad wings in the [C II] lines, signatures of starburst-driven outflows. We infer an average outflow rate of. M(over dot) = 54 +/- 23M(circle dot) yr(-1), providing a loading factor eta = M(over dot)/SFR = 1.7 +/- 1.3 in agreement with observed local starbursts. Our interpretation is consistent with outcomes from zoomed hydrosimulations of Dahlia, a z similar to 6 galaxy (SFR similar to 100M(circle dot) yr(-1)), whose feedback-regulated star formation results into an outflow rate. M(over dot) similar to 30M(circle dot) yr(-1). The quality of the ALMA data is not sufficient for a detailed analysis of the [C II] line profile in individual galaxies. Nevertheless, our results suggest that starburst-driven outflows are in place in the EoR and provide useful indications for future ALMA campaigns. Deeper observations of the [C II] line in this sample are required to better characterize feedback at high-z and to understand the role of outflows in shaping early galaxy formation.

  • 11. Kohandel, M.
    et al.
    Pallottini, A.
    Ferrara, A.
    Zanella, A.
    Behrens, C.
    Carniani, S.
    Gallerani, S.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Leiden University, the Netherlands.
    Kinematics of z >= 6 galaxies from [C II] line emission2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 487, no 3, p. 3007-3020Article in journal (Refereed)
    Abstract [en]

    We study the kinematical properties of galaxies in the Epoch of Reionization via the [C II] 158 mu m line emission. The line profile provides information on the kinematics as well as structural properties such as the presence of a disc and satellites. To understand how these properties are encoded in the line profile, first we develop analytical models from which we identify disc inclination and gas turbulent motions as the key parameters affecting the line profile. To gain further insights, we use 'Althaea', a highly resolved (30 pc) simulated prototypical Lyman-break galaxy, in the redshilt range z = 6-7, when the galaxy is in a very active assembling phase. Based on morphology, we select three main dynamical stages: (I) merger, (II) spiral disc, and (III) disturbed disc, We identify spectral signatures of merger events, spiral arms, and extra-planar flows in (1), (II), and respectively. We derive a generalized dynamical mass versus [C II]-line FWHM relation. If precise information on the galaxy inclination is (not) available, the returned mass estimate is accurate within a factor 2 (4). A Tully-Fisher relation is found for the observed high-z galaxies, i.e. L-[C II] proportional to (FWHM)(1.80 +/- 0.35) for which we provide a simple, physically based interpretation, Finally, we perform mock ALMA simulations to check the detectability of [C II]. When seen face-on, Althaea is always detected at >5 sigma; in the edge-on case it remains undetected because the larger intrinsic FWIIM pushes the line peak flux below detection limit. This suggests that some of the reported non-detections might be due to inclination effects.

  • 12. Matthee, J.
    et al.
    Sobral, D.
    Boone, F.
    Röttgering, H.
    Schaerer, D.
    Girard, M.
    Pallottini, A.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Ferrara, A.
    Darvish, B.
    Mobasher, B.
    ALMA Reveals Metals yet No Dust within Multiple Components in CR72017In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 851, no 2, article id 145Article in journal (Refereed)
    Abstract [en]

    We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [C II](158 mu m) line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Ly alpha emitting galaxy at z = 6.6 that consists of three separated UV-continuum components. Our observations reveal several well-separated components of [C II] emission. The two most luminous components in [C II] coincide with the brightest UV components (A and B), blueshifted by approximate to 150 km s(-1) with respect to the peak of Lya emission. Other [C II] components are observed close to UV clumps B and C and are blueshifted by approximate to 300 and approximate to 80 km s(-1) with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3 sigma limiting luminosity L-IR(T-d = 35 K) < 3.1 x 10(10) L-circle dot. This allows us to mitigate uncertainties in the dust-corrected SFR and derive SFRs for the three UV clumps A, B, and C of 28, 5, and 7 M-circle dot yr(-1). All clumps have [C II] luminosities consistent within the scatter observed in the local relation between SFR and L[C II], implying that strong Ly alpha emission does not necessarily anti-correlate with [C II] luminosity. Combining our measurements with the literature, we show that galaxies with blue UV slopes have weaker [C II] emission at fixed SFR, potentially due to their lower metallicities and/or higher photoionization. Comparison with hydrodynamical simulations suggests that CR7's clumps have metallicities of 0.1 < Z/Z(circle dot) < 0.2. The observed ISM structure of CR7 indicates that we are likely witnessing the build up of a central galaxy in the early universe through complex accretion of satellites.

  • 13. Mingozzi, M.
    et al.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Pozzi, F.
    Vignali, C.
    Mignano, A.
    Gruppioni, C.
    Talia, M.
    Cimatti, A.
    Cresci, G.
    Massardi, M.
    CO excitation in the Seyfert galaxy NGC 34: stars, shock or AGN driven?2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 474, no 3, p. 3640-3648Article in journal (Refereed)
    Abstract [en]

    We present a detailed analysis of the X-ray and molecular gas emission in the nearby galaxy NGC 34, to constrain the properties of molecular gas, and assess whether, and to what extent, the radiation produced by the accretion on to the central black hole affects the CO line emission. We analyse the CO spectral line energy distribution (SLED) as resulting mainly from Herschel and ALMA data, along with X-ray data from NuSTAR and XMM-Newton. The X-ray data analysis suggests the presence of a heavily obscured active galactic nucleus (AGN) with an intrinsic luminosity of L1-100 (keV) similar or equal to 4.0 x 10(42) erg s(-1). ALMA high-resolution data (theta similar or equal to 0.2 arcsec) allow us to scan the nuclear region down to a spatial scale of approximate to 100 pc for the CO(6-5) transition. We model the observed SLED using photodissociation region (PDR), X-ray-dominated region (XDR), and shock models, finding that a combination of a PDR and an XDR provides the best fit to the observations. The PDR component, characterized by gas density log(n/cm(-3)) = 2.5 and temperature T = 30 K, reproduces the low-J CO line luminosities. The XDR is instead characterized by a denser and warmer gas (log(n/cm(-3)) = 4.5, T = 65 K), and is necessary to fit the high-J transitions. The addition of a third component to account for the presence of shocks has been also tested but does not improve the fit of the CO SLED. We conclude that the AGN contribution is significant in heating the molecular gas in NGC 34.

  • 14. Pallottini, A.
    et al.
    Ferrara, A.
    Decataldo, D.
    Gallerani, S.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Leiden University, the Netherlands.
    Carniani, S.
    Behrens, C.
    Kohandel, M.
    Salvadori, S.
    Deep into the structure of the first galaxies: SERRA views2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 487, no 2, p. 1689-1708Article in journal (Refereed)
    Abstract [en]

    We study the formation and evolution of a sample of Lyman break galaxies in the epoch of reionization by using high-resolution (similar to 10 pc), cosmological zoom-in simulations part of the SERRA suite. In SERRA, we follow the interstellar medium thermochemical non-equilibrium evolution and perform on-the-fly radiative transfer of the interstellar radiation field (ISRF). The simulation outputs are post-processed to compute the emission of far infrared lines ([C II], [N II], and [O III]). At z = 8, the most massive galaxy, 'Freesia', has an age t(star) similar or equal to 409 Myr, stellar mass M-star similar or equal to 4.2 x 10(9)M(circle dot), and a star formation rate (SFR), SFR similar or equal to 11.5M(circle dot) yr(-1), due to a recent burst. Freesia has two stellar components (A and B) separated by similar or equal to 2.5 kpc; other 11 galaxies are found within 56.9 +/- 21.6 kpc. The mean ISRF in the Habing band is G = 7.9G(0) and is spatially uniform; in contrast, the ionization parameter is U = 2(-2)(+20) x 10(-3), and has a patchy distribution peaked at the location of star-forming sites. The resulting ionizing escape fraction from Freesia is f(esc) similar or equal to 2 per cent. While [C II] emission is extended (radius 1.54 kpc), [O III] is concentrated in Freesia-Lambda (0.85 kpc), where the ratio Sigma([O III])/Sigma([C II]) similar or equal to 10. As many high-z galaxies, Freesia lies below the local [C II]-SFR relation. We show that this is the general consequence of a starburst phase (pushing the galaxy above the Kennicutt-Schmidt relation) that disrupts/photodissociates the emitting molecular clouds around star-forming sites. Metallicity has a sub-dominant impact on the amplitude of [C II]-SFR deviations.

  • 15. Pallottini, Andrea
    et al.
    Ferrara, A.
    Bovino, S.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Gallerani, S.
    Maiolino, R.
    Salvadori, S.
    The impact of chemistry on the structure of high-z galaxies2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 471, no 4, p. 4128-4143Article in journal (Refereed)
    Abstract [en]

    To improve our understanding of high-z galaxies, we study the impact of H-2 chemistry on their evolution, morphology and observed properties. We compare two zoom-in high-resolution (30 pc) simulations of prototypical M-star similar to 1010M(circle dot) galaxies at z = 6. The first, 'Dahlia', adopts an equilibrium model for H-2 formation, while the second, 'Alth ae a', features an improved non-equilibrium chemistry network. The star formation rate (SFR) of the two galaxies is similar (within 50 per cent), and increases with time reaching values close to 100M(circle dot) yr(-1) at z = 6. They both have SFR-stellar mass relation consistent with observations, and a specific SFR of similar or equal to 5Gyr(-1). The main differences arise in the gas properties. The non-equilibrium chemistry determines the H -> H-2 transition to occur at densities > 300 cm(-3), i.e. about 10 times larger than predicted by the equilibrium model used for Dahlia. As a result, Alth ae a features a more clumpy and fragmented morphology, in turn makingSNfeedback more effective. Also, because of the lower density and weaker feedback, Dahlia sits 3 sigma away from the Schmidt-Kennicutt relation; Alth ae a, instead nicely agrees with observations. The different gas properties result in widely different observables. Alth ae a outshines Dahlia by a factor of 7 (15) in [C (II)] 157.74 mu m (H(2)17.03 mu m) line emission. Yet, Alth ae a is underluminous with respect to the locally observed [C (II)]-SFR relation. Whether this relation does not apply at high-z or the line luminosity is reduced by cosmic microwave background and metallicity effects remain as an open question.

  • 16. Pozzi, F.
    et al.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Vignali, C.
    Talia, M.
    Gruppioni, C.
    Mingozzi, M.
    Massardi, M.
    Andreani, P.
    CO excitation in the Seyfert galaxy NGC 71302017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 470, no 1, p. L64-L68Article in journal (Refereed)
    Abstract [en]

    We present a coherent multiband modelling of the carbon monoxide (CO) spectral energy distribution of the local Seyfert galaxy NGC 7130 to assess the impact of the active galactic nucleus (AGN) activity on the molecular gas. We take advantage of all the available data from X-ray to the submillimetre, including ALMA data. The high-resolution (similar to 0.2 arcsec) ALMA CO(6-5) data constrain the spatial extension of the CO emission down to an similar to 70 pc scale. From the analysis of the archival Chandra and NuSTAR data, we infer the presence of a buried, Compton-thick AGN of moderate luminosity, L2-10 (keV) similar to 1.6 x 10(43) erg s(-1). We explore photodissociation and X-ray-dominated-region (PDR and XDR) models to reproduce the CO emission. We find that PDRs can reproduce the CO lines up to J similar to 6; however, the higher rotational ladder requires the presence of a separate source of excitation. We consider X-ray heating by the AGNs as a source of excitation, and find that it can reproduce the observed CO spectral energy distribution. By adopting a composite PDR+XDR model, we derive molecular cloud properties. Our study clearly indicates the capabilities offered by the current generation of instruments to shed light on the properties of nearby galaxies by adopting state-of-the-art physical modelling.

  • 17. Spinoglio, L.
    et al.
    Alonso-Herrero, A.
    Armus, L.
    Baes, M.
    Bernard-Salas, J.
    Bianchi, S.
    Bocchio, M.
    Bolatto, A.
    Bradford, C.
    Braine, J.
    Carrera, F. J.
    Ciesla, L.
    Clements, D. L.
    Dannerbauer, H.
    Doi, Y.
    Efstathiou, A.
    Egami, E.
    Fernandez-Ontiveros, J. A.
    Ferrara, A.
    Fischer, J.
    Franceschini, A.
    Gallerani, S.
    Giard, M.
    Gonzalez-Alfonso, E.
    Gruppioni, C.
    Guillard, P.
    Hatziminaoglou, E.
    Imanishi, M.
    Ishihara, D.
    Isobe, N.
    Kaneda, H.
    Kawada, M.
    Kohno, K.
    Kwon, J.
    Madden, S.
    Malkan, M. A.
    Marassi, S.
    Matsuhara, H.
    Matsuura, M.
    Miniutti, G.
    Nagamine, K.
    Nagao, T.
    Najarro, F.
    Nakagawa, T.
    Onaka, T.
    Oyabu, S.
    Pallottini, A.
    Piro, L.
    Pozzi, F.
    Rodighiero, G.
    Roelfsema, P.
    Sakon, I.
    Santini, P.
    Schaerer, D.
    Schneider, R.
    Scott, D.
    Serjeant, S.
    Shibai, H.
    Smith, J. -D. T.
    Sobacchi, E.
    Sturm, E.
    Suzuki, T.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Osservatorio Astronomico di Bologna, INAF, Italy; Universitá di Bologna, Italy.
    van der Tak, F.
    Vignali, C.
    Yamada, T.
    Wada, T.
    Wang, L.
    Galaxy Evolution Studies with the &ITSPace IR Telescope for Cosmology and Astrophysics&IT (&ITSPICA&IT): The Power of IR Spectroscopy2017In: Publications Astronomical Society of Australia, ISSN 1323-3580, E-ISSN 1448-6083, Vol. 34, article id e057Article in journal (Refereed)
    Abstract [en]

    IR spectroscopy in the range 12-230 mu m with the SPace IR telescope for Cosmology and Astrophysics (SPICA) will reveal the physical processes governing the formation and evolution of galaxies and black holes through cosmic time, bridging the gap between the James Webb Space Telescope and the upcoming Extremely Large Telescopes at shorter wavelengths and the Atacama Large Millimeter Array at longer wavelengths. The SPICA, with its 2.5-m telescope actively cooled to below 8 K, will obtain the first spectroscopic determination, in the mid-IR rest-frame, of both the star-formation rate and black hole accretion rate histories of galaxies, reaching lookback times of 12 Gyr, for large statistically significant samples. Densities, temperatures, radiation fields, and gas-phase metallicities will be measured in dust-obscured galaxies and active galactic nuclei, sampling a large range in mass and luminosity, from faint local dwarf galaxies to luminous quasars in the distant Universe. Active galactic nuclei and starburst feedback and feeding mechanisms in distant galaxies will be uncovered through detailed measurements of molecular and atomic line profiles. The SPICA's large-area deep spectrophotometric surveys will provide mid-IR spectra and continuum fluxes for unbiased samples of tens of thousands of galaxies, out to redshifts of z similar to 6.

  • 18. Talia, M.
    et al.
    Pozzi, F.
    Vallini, Livia
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Cimatti, A.
    Cassata, P.
    Fraternali, F.
    Brusa, M.
    Daddi, E.
    Delvecchio, I.
    Ibar, E.
    Liuzzo, E.
    Vignali, C.
    Massardi, M.
    Zamorani, G.
    Gruppioni, C.
    Renzini, A.
    Mignoli, M.
    Pozzetti, L.
    Rodighiero, G.
    ALMA view of a massive spheroid progenitor: a compact rotating core of molecular gas in an AGN host at z=2.2262018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 476, no 3, p. 3956-3963Article in journal (Refereed)
    Abstract [en]

    We present ALMA observations at 107.291 GHz (band 3) and 214.532 GHz (band 6) of GMASS 0953, a star-forming galaxy at z = 2.226 hosting an obscured active galactic nucleus (AGN) that has been proposed as a progenitor of compact quiescent galaxies (QGs). We measure for the first time the size of the dust and molecular gas emission of GMASS 0953 that we find to be extremely compact (similar to 1 kpc). This result, coupled with a very high interstellar medium (ISM) density (n similar to 10(5.5) cm(-3)), a low gas mass fraction (similar to 0.2), and a short gas depletion time-scale (similar to 150 Myr), implies that GMASS 0953 is experiencing an episode of intense star formation in its central region that will rapidly exhaust its gas reservoirs, likely aided by AGN-induced feedback, confirming its fate as a compact QG. Kinematic analysis of the CO(6-5) line shows evidence of rapidly rotating gas (V-rot = 320(-53)(+92) km s(-1)), as observed also in a handful of similar sources at the same redshift. On-going quenching mechanisms could either destroy the rotation or leave it intact leading the galaxy to evolve into a rotating QG.

  • 19.
    Vallini, Livia
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Dipartimento di Fisica e Astronomia, Bologna, Italy; INAF, Osservatorio Astronomico di Bologna, Italy.
    Ferrara, A.
    Pallottini, A.
    Gallerani, S.
    Molecular cloud photoevaporation and far-infrared line emission2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 467, no 2, p. 1300-1312Article in journal (Refereed)
    Abstract [en]

    With the aim of improving predictions on far-infrared (FIR) line emission from Giant Molecular Clouds (GMCs), we study the effects of photoevaporation (PE) produced by external farultraviolet (FUV) and ionizing (extreme-ultraviolet) radiation on GMC structure. We consider three different GMCs with mass in the range M-GMC = 10(3)-10(6)M(O). Our model includes (i) an observationally based inhomogeneous GMC density field, and (ii) its time evolution during the PE process. In the fiducial case (M-GMC approximate to 10(5)M(O)), the PE time (t(pe)) increases from 1 to 30 Myr for gasmetallicityZ = 0.05-1 Z(O)), respectively. Next, we compute the time-dependent luminosity of key FIR lines tracing the neutral and ionized gas layers of the GMCs, ([C II] at 158 mu m, [O III] at 88 mu m) as a function of G(0), and Z until complete PE at t(pe). We find that the specific [C II] luminosity is almost independent of the GMC model within the survival time of the cloud. Stronger FUV fluxes produce higher [C II] and [O III] luminosities, however, lasting for progressively shorter times. At Z = Z(O), the [CII] emission is maximized (LCII approximate to 10(4) L-O for the fiducial model) for t < 1Myr and logG(0) >= 3. Noticeably, and consistently with the recent detection by Inoue et al. of a galaxy at redshift z approximate to 7.2, for Z = 0.2Z(O), the [OIII] line might outshine [C II] emission by up to approximate to 1000 times. We conclude that the [OIII] line is a key diagnostic of low-metallicity interstellar medium, especially in galaxies with very young stellar populations.

  • 20.
    Vallini, Livia
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Pallottini, A.
    Ferrara, A.
    Gallerani, S.
    Sobacchi, E.
    Behrens, C.
    CO line emission from galaxies in the Epoch of Reionization2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 1, p. 271-285Article in journal (Refereed)
    Abstract [en]

    We study the CO line luminosity (L-CO), the shape of the CO spectral line energy distribution (SLED), and the value of the CO-to-H-2 conversion factor in galaxies in the Epoch of Reionization (EoR). For this aim, we construct a model that simultaneously takes into account the radiative transfer and the clumpy structure of giant molecular clouds (GMCs) where the CO lines are excited. We then use it to post-process state-of-the-art zoomed, high resolution (30 pc), cosmological simulation of a main-sequence (M-* approximate to 10(10) M-circle dot, SFR approximate to 100M(circle dot) yr(-1)) galaxy, 'Althaea', at z approximate to 6. We find that the CO emission traces the inner molecular disc (r approximate to 0.5 kpc) of Althaea with the peak of the CO surface brightness co-located with that of the [C-II] 158 mu m emission. Its LCO(1-0) = 10(4.85) L-circle dot is comparable to that observed in local galaxies with similar stellar mass. The high (Sigma(gas) approximate to 220M(circle dot) pc(-2)) gas surface density in Althaea, its large Mach number (M approximate to 30) and the warm kinetic temperature (T-k approximate to 45 K) of GMCs yield a CO SLED peaked at the CO(7-6) transition, i.e. at relatively high-J and a CO-to-H-2 conversion factor alpha(CO) approximate to 1.5M(circle dot) (K km s(-1) pc(2))(-1) lower than that of the Milky Way. The Atacama Large Millimeter/submillimeter Array observing time required to detect (resolve) at 5 sigma the CO(7-6) line from galaxies similar to Althaea is approximate to 13 h (approximate to 38 h).

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