Scholarly Works - Physics - Astrophysics


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  • ItemAccepted versionOpen Access
    Kiloparsec-scale gaseous clumps and star formation at z = 5–7
    (Oxford University Press, 2018) Carniani, Stefano; Maiolino, Roberto; Amorin, Ricardo; Pentericci, Laura; Pallottini, Andrea; Ferrara, Andrea; Willott, Chris; Smit, Renske; Mathee, J; Sobral, David; Santini, Paola; Castellano, Marco; De Barros, Stephan; Fontana, Adriano; Grazian, Andrea; Guaita, Lucia; Carniani, Stefano [0000-0002-6719-380X]; Maiolino, Roberto [0000-0002-4985-3819]; Amorin Barbieri, Ricardo [0000-0001-5758-1000]; Pallottini, Andrea [0000-0002-7129-5761]; Smit, Renske [0000-0001-8034-7802]
    We investigate the morphology of the [Cii] emission in a sample of “normal” star-forming galaxies at 5 < z < 7:2 in relation to their UV (rest-frame) counterpart. We use new ALMA observations of galaxies at z 6 7, as well as a careful re-analysis of archival ALMA data. In total 29 galaxies were analysed, 21 of which are detected in [Cii]. For several of the latter the [Cii] emission breaks into multiple components. Only a fraction of these [Cii] components, if any, is associated with the primary UV systems, while the bulk of the [Cii] emission is associated either with fainter UV components, or not associated with any UV counterpart at the current limits. By taking into account the presence of all these components, we find that the L[CII]-SFR relation at early epochs is fully consistent with the local relation, but it has a dispersion of 0.48 0.07 dex, which is about two times larger than observed locally. We also find that the deviation from the local L[CII]-SFR relation has a weak anti-correlation with the EW(Ly ). The morphological analysis also reveals that [Cii] emission is generally much more extended than the UV emission. As a consequence, these primordial galaxies are characterised by a [Cii] surface brightness generally much lower than expected from the local [CII] SFR relation. These properties are likely a consequence of a combination of di erent e ects, namely: gas metallicity, [Cii] emission from obscured star-forming regions, strong variations of the ionisation parameter, and circumgalactic gas in accretion or ejected by these primeval galaxies.
  • ItemPublished versionOpen Access
    Extended and broad Ly α emission around a BAL quasar at z ∼ 5
    (Oxford University Press, 2018) Ginolfi, Michele; Maiolino, Roberto; Carniani, Stefano; Battaia, Fabrizio Arrigoni; Cantalupo, Sebastiano; Schneider, Raffaella; Maiolino, Roberto [0000-0002-4985-3819]; Carniani, Stefano [0000-0002-6719-380X]
    In this work we report deep MUSE observations of a broad absorption line (BAL) quasar at z ∼ 5, revealing a Ly α nebula with a maximum projected linear size of ∼60 kpc around the quasar (down to our 2σ SB limit per layer of ∼9×10−19ergs−1cm−2arcsec−2 for a 1 arcsec2 aperture). After correcting for the cosmological surface brightness dimming, we find that our nebula, at z ∼ 5, has an intrinsically less extended Ly α emission than nebulae at lower redshift. However, such a discrepancy is greatly reduced when referring to comoving distances, which take into account the cosmological growth of dark matter (DM) haloes, suggesting a positive correlation between the size of Ly α nebulae and the sizes of DM haloes/structures around quasars. Differently from the typical nebulae around radio-quiet non-BAL quasars, in the inner regions (∼10 kpc) of the circumgalactic medium of our source, the velocity dispersion of the Ly α emission is very high (FWHM > 1000 km s−1), suggesting that in our case we may be probing outflowing material associated with the quasar.
  • ItemAccepted versionOpen Access
    Characterization of star-forming dwarf galaxies at 0.1 ≲ z ≲ 0.9 in VUDS: Probing the low-mass end of the mass-metallicity relation
    (EDP Sciences, 2017) Calabrò, A; Amorín, R; Fontana, A; Pérez-Montero, E; Lemaux, BC; Ribeiro, B; Bardelli, S; Castellano, M; Contini, T; De Barros, S; Garilli, B; Grazian, A; Guaita, L; Hathi, NP; Koekemoer, AM; Le Fèvre, O; MacCagni, D; Pentericci, L; Schaerer, D; Talia, M; Tasca, LAM; Zucca, E; Amorin Barbieri, Ricardo [0000-0001-5758-1000]
    We present the discovery and spectrophotometric characterization of a large sample of 164 faint ($i_{AB}$ $\sim$ $23$-$25$ mag) star-forming dwarf galaxies (SFDGs) at redshift $0.13$ $\leq z \leq$ $0.88$ selected by the presence of bright optical emission lines in the VIMOS Ultra Deep Survey (VUDS). We investigate their integrated physical properties and ionization conditions, which are used to discuss the low-mass end of the mass-metallicity relation (MZR) and other key scaling relations. We use optical VUDS spectra in the COSMOS, VVDS-02h, and ECDF-S fields, as well as deep multiwavelength photometry, to derive stellar masses, star formation rates (SFR) and gas-phase metallicities. The VUDS SFDGs are compact (median $r_{e}$ $\sim$ $1.2$ kpc), low-mass ($M_{*}$ $\sim$ $10^7-10^9$ $M_{\odot}$) galaxies with a wide range of star formation rates (SFR($H\alpha$) $\sim 10^{-3}-10^{1}$ $M_{\odot}/yr$) and morphologies. Overall, they show a broad range of subsolar metallicities (12+log(O/H)=$7.26$-$8.7$; $0.04$ $\lesssim Z/Z_{\odot} \lesssim$ $1$). The MZR of SFDGs shows a flatter slope compared to previous studies of galaxies in the same mass range and redshift. We find the scatter of the MZR partly explained in the low mass range by varying specific SFRs and gas fractions amongst the galaxies in our sample. Compared with simple chemical evolution models we find that most SFDGs do not follow the predictions of a "closed-box" model, but those from a gas regulating model in which gas flows are considered. While strong stellar feedback may produce large-scale outflows favoring the cessation of vigorous star formation and promoting the removal of metals, younger and more metal-poor dwarfs may have recently accreted large amounts of fresh, very metal-poor gas, that is used to fuel current star formation.
  • ItemAccepted versionOpen Access
    The VIMOS Ultra-Deep Survey: A major merger origin for the high fraction of galaxies at 2 < z < 6 with two bright clumps
    (EDP Sciences, 2017) Ribeiro, B; Le Fèvre, O; Cassata, P; Garilli, B; Lemaux, BC; Maccagni, D; Schaerer, D; Tasca, LAM; Zamorani, G; Zucca, E; Amorín, R; Bardelli, S; Hathi, NP; Koekemoer, A; Pforr, J; Amorin Barbieri, Ricardo [0000-0001-5758-1000]
    (Abridged) The properties of stellar clumps in star forming galaxies and their evolution over the redshift range $2\lesssim z \lesssim 6$ are presented and discussed in the context of the build-up of massive galaxies at early cosmic times. We use HST/ACS images of galaxies with spectroscopic redshifts from the VIMOS Ultra Deep Survey (VUDS) to identify clumps within a 20 kpc radius. We find that the population of galaxies with more than one clump is dominated by galaxies with two clumps, representing $\sim21-25$\% of the population, while the fraction of galaxies with 3, or 4 and more, clumps is 8-11 and 7-9\%, respectively. The fraction of clumpy galaxies is in the range $\sim35-55\%$ over $2
  • ItemAccepted versionOpen Access
    The MUSE view of the host galaxy of GRB 100316D
    (Oxford University Press (OUP), 2017) Izzo, L; Thäone, CC; Schulze, S; Mehner, A; Flores, H; Cano, Z; de Ugarte Postigo, A; Kann, DA; Amoŕin, R; Anderson, JP; Bauer, FE; Bensch, K; Christensen, L; Covino, S; Valle, MD; Fynbo, JPU; Jakobsson, P; Klose, S; Kuncarayakti, H; Leloudas, G; Milvang-Jensen, B; Møller, P; Puech, M; Rossi, A; Sánchez-Raḿirez, R; Vergani, SD
    The low distance, $z=0.0591$, of GRB 100316D and its association with SN 2010bh represent two important motivations for studying this host galaxy and the GRB's immediate environment with the Integral-Field Spectrographs like VLT/MUSE. Its large field-of-view allows us to create 2D maps of gas metallicity, ionization level, and the star-formation rate distribution maps, as well as to investigate the presence of possible host companions. The host is a late-type dwarf irregular galaxy with multiple star-forming regions and an extended central region with signatures of on-going shock interactions. The GRB site is characterized by the lowest metallicity, the highest star-formation rate and the youngest ($\sim$ 20-30 Myr) stellar population in the galaxy, which suggest a GRB progenitor stellar population with masses up to 20 -- 40 $M_{\odot}$. We note that the GRB site has an offset of $\sim$660pc from the most luminous SF region in the host. The observed SF activity in this galaxy may have been triggered by a relatively recent gravitational encounter between the host and a small undetected ($L_{H\alpha} \leq 10^{36}$ erg/s) companion.
  • ItemAccepted versionOpen Access
    The supermassive black hole coincident with the luminous transient ASASSN-15lh
    (EDP Sciences, 2018-04-01) Krühler, T; Fraser, M; Leloudas, G; Schulze, S; Stone, NC; Van Velzen, S; Amorin, R; Hjorth, J; Jonker, PG; Kann, DA; Kim, S; Kuncarayakti, H; Mehner, A; Nicuesa Guelbenzu, A; Amorin Barbieri, Ricardo [0000-0001-5758-1000]
    The progenitors of astronomical transients are linked to a specific stellar population and galactic environment, and observing their host galaxies hence constrains the physical nature of the transient itself. Here, we use imaging from the Hubble Space Telescope, and spatially resolved, medium-resolution spectroscopy from the Very Large Telescope obtained with X-shooter and MUSE to study the host of the very luminous transient ASASSN-15lh. The dominant stellar population at the transient site is old (around 1 to 2 Gyr) without signs of recent star formation. We also detect emission from ionized gas, originating from three different, time invariable, narrow components of collisionally excited metal and Balmer lines. The ratios of emission lines in the Baldwin-Phillips-Terlevich diagnostic diagram indicate that the ionization source is a weak active galactic nucleus with a black hole mass of M•= 5-3+8× 108MâŠ, derived through the M•-σ relation. The narrow line components show spatial and velocity offsets on scales of 1 kpc and 500 km s-1, respectively; these offsets are best explained by gas kinematics in the narrow-line region. The location of the central component, which we argue is also the position of the supermassive black hole, aligns with that of the transient within an uncertainty of 170 pc. Using this positional coincidence as well as other similarities with the hosts of tidal disruption events, we strengthen the argument that the transient emission observed as ASASSN-15lh is related to the disruption of a star around a supermassive black hole, most probably spinning with a Kerr parameter a•â0.5.
  • ItemOpen Access
    Lyα-Lyman continuum connection in 3:5 ≤ z ≤ 4:3 star-forming galaxies from the VUDS survey
    (EDP Sciences, 2018-06-06) Marchi, F; Pentericci, L; Guaita, L; Schaerer, D; Verhamme, A; Castellano, M; Ribeiro, B; Garilli, B; Fèvre, OL; Amorin, R; Bardelli, S; Cassata, P; Durkalec, A; Grazian, A; Hathi, NP; Lemaux, BC; Maccagni, D; Vanzella, E; Zucca, E; Amorin Barbieri, Ricardo [0000-0001-5758-1000]
    © ESO 2018. Context. To identify the galaxies responsible for the reionization of the Universe, we must rely on the investigation of the Lyman continuum (LyC) properties of z . 5 star-forming galaxies, where we can still directly observe their ionizing radiation. Aims. The aim of this work is to explore the correlation between the LyC emission and some of the proposed indirect indicators of LyC radiation at z 4 such as a bright Lyα emission and a compact UV continuum size. Methods. We selected a sample of 201 star-forming galaxies from the Vimos Ultra Deep Survey (VUDS) at 3:5 ≤ z ≤ 4:3 in the COSMOS, ECDFS, and VVDS-2h fields, including only those with reliable spectroscopic redshifts, a clean spectrum in the LyC range and clearly not contaminated by bright nearby sources in the same slit. For all galaxies we measured the Lyα EW, the Lyα velocity shift with respect to the systemic redshift, the Lyα spatial extension and the UV continuum effective radius. We then selected different sub-samples according to the properties predicted to be good LyC emission indicators: in particular we created sub-samples of galaxies with EW(Lyα) λ 70, Lyαext ≤ 5:7 kpc, rUV ≤ 0:30 kpc and jΔvLyαj ≤ 200 km s-1. We stacked all the galaxies in each sub-sample and measured the flux density ratio ( fλ(895)= fλ(1470)), that we considered to be a proxy for LyC emission. We then compared these ratios to those obtained for the complementary samples. Finally, to estimate the statistical contamination from lower redshift inter-lopers in our samples, we performed dedicated Monte Carlo simulations using an ultradeep U-band image of the ECDFS field. Results. We find that the stacks of galaxies which are UV compact (rUV ≤ 0:30 kpc) and have bright Lyα emission (EW(Lyα) λ 70), have much higher LyC fluxes compared to the rest of the galaxy population. These parameters appear to be good indicators of LyC radiation in agreement with theoretical studies and previous observational works. In addition we find that galaxies with a low Lyα spatial extent (Lyαext ≤ 5:7 kpc) have higher LyC flux compared to the rest of the population. Such a correlation had never been analysed before and seems even stronger than the correlation with high EW(Lyα) and small rUV . These results assume that the stacks from all sub-samples present the same statistical contamination from lower redshift interlopers. If we subtract a statistical contamination from low redshift interlopers obtained with the simulations from the flux density ratios ( fλ(895)= fλ(1470)) of the significant sub-samples we find that these samples contain real LyC leaking flux with a very high probability, although the true average escape fractions are very uncertain. Conclusions. Our work indicates that galaxies with very high EW(Lyα), small Lyαext and small rUV are very likely the best candidates to show Lyman continuum radiation at z 4 and could therefore be the galaxies that have contributed most to reionisation.
  • ItemOpen Access
    The HOSTS Survey—Exozodiacal Dust Measurements for 30 Stars
    (American Astronomical Society, 2018) Ertel, S; Defrère, D; Hinz, P; Mennesson, B; Kennedy, GM; Danchi, WC; Gelino, C; Hill, JM; Hoffmann, WF; Rieke, G; Shannon, A; Spalding, E; Stone, Jordan M; Vaz, A; Weinberger, AJ; Willems, P; Absil, O; Arbo, P; Bailey, VP; Beichman, C; Bryden, G; Downey, EC; Durney, O; Esposito, S; Gaspar, A; Grenz, P; Haniff, CA; Leisenring, JM; Marion, L; McMahon, TJ; Millan-Gabet, R; Montoya, M; Morzinski, KM; Pinna, E; Power, J; Puglisi, A; Roberge, A; Serabyn, E; Skemer, AJ; Stapelfeldt, K; Su, KYL; Vaitheeswaran, V; Wyatt, MC; Kennedy, Grant [0000-0001-6831-7547]; Haniff, Christopher [0000-0001-8726-5797]; Wyatt, Mark [0000-0001-9064-5598]
    The HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey searches for dust near the habitable zones (HZs) around nearby, bright main sequence stars. We use nulling interferometry in N band to suppress the bright stellar light and to probe for low levels of HZ dust around the 30 stars observed so far. Our overall detection rate is 18%, including four new detections, among which are the first three around Sun-like stars and the first two around stars without any previously known circumstellar dust. The inferred occurrence rates are comparable for early type and Sun-like stars, but decrease from 60 (+16/-21)% for stars with previously detected cold dust to 8 (+10/-3)% for stars without such excess, confirming earlier results at higher sensitivity. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal excess luminosity function, we put upper limits on the median HZ dust level of 13 zodis (95% confidence) for a sample of stars without cold dust and of 26 zodis when focussing on Sun-like stars without cold dust. However, our data suggest that a more complex luminosity function may be more appropriate. For stars without detectable LBTI excess, our upper limits are almost reduced by a factor of two, demonstrating the strength of LBTI target vetting for future exo-Earth imaging missions. Our statistics are so far limited and extending the survey is critical to inform the design of future exo-Earth imaging surveys.
  • ItemAccepted versionOpen Access
    Outflows and complex stellar kinematics in SDSS star-forming galaxies
    (EDP Sciences, 2016-04-01) Cicone, C; Maiolino, R; Marconi, A; Maiolino, Roberto [0000-0002-4985-3819]
    We investigate the properties of star-formation-driven outflows by using a large spectroscopic sample of ∼160 000 local "normal" star-forming galaxies drawn from the Sloan digital sky survey (SDSS), spanning a wide range of star formation rates (SFRs) and stellar masses (M∗). The galaxy sample is divided into a fine grid of bins in the M∗-SFR parameter space, for each of which we produced a composite spectrum by stacking the SDSS spectra of the galaxies contained in that bin together. We exploited the high signal-to-noise of the stacked spectra to study the emergence of faint features of optical emission lines that may trace galactic outflows and are otherwise too faint to detect in individual galaxy spectra. We have adopted a novel approach that relies on the comparison between the line-of-sight velocity distribution (LoSVD) of the ionised gas (as traced by the [OIII]λ5007 and Hα+[NII]λλ6548, 6583 emission lines) and the LoSVD of the stars, which are used as a reference for tracing virial motions. Significant deviations in the gas kinematics from the stellar kinematics in the high-velocity tail of the LoSVDs are interpreted as a signature of outflows. Our results suggest that the incidence of ionised outflows increases with SFR and specific SFR. The outflow velocity (vout) is found to correlate tightly with the SFR for SFR> 1 M⊙yr-1, whereas the dependence of vouton SFR is nearly flat at lower SFRs. The outflow velocity appears to also increase with the stellar velocity dispersion (σ∗), although this relation has a much larger scatter than the one with SFR, and we infer velocities as high as vout∼ (6-8)σ∗. Strikingly, we detect the signature of ionised outflows only in galaxies located above the main sequence (MS) of star-forming galaxies in the M∗-SFR diagram, and the incidence of such outflows increases sharply with the offset from the MS. This result suggests that star-formation-driven outflows may be responsible for shaping the upper envelope of the MS by providing a self-regulating mechanism for star formation. Finally, our complementary analysis of the stellar kinematics reveals the presence of blue asymmetries of a few 10 km s-1in the stellar LoSVDs. The origin of such asymmetries is not clear, but a possibility is that they trace the presence of a large number of high velocity runaway stars and hypervelocity stars in radial trajectories in local galaxies.
  • ItemPublished versionOpen Access
    Galaxy metallicities depend primarily on stellar mass and molecular gas mass
    (EDP Sciences, 2016-11-01) Bothwell, MS; Maiolino, R; Cicone, C; Peng, Y; Wagg, J; Maiolino, Roberto [0000-0002-4985-3819]
    Aims. We present an analysis of the behaviour of galaxies in a four-dimensional parameter space defined by stellar mass, metallicity, star formation rate, and molecular gas mass. We analyse a combined sample of 227 galaxies that draws from a number of surveys across the redshift range 0 < z < 2 (>90% of the sample at z ~ 0) and covers >3 decades in stellar mass. Methods. Using principal component analysis, we demonstrate that galaxies in our sample lie on a 2D plane within this 4D parameter space, which is indicative of galaxies that exist in an equilibrium between gas inflow and outflow. Furthermore, we find that the metallicity of galaxies depends only on stellar mass and molecular gas mass. In other words, gas-phase metallicity has a negligible dependence on star formation rate once the correlated effect of molecular gas content is accounted for. Results. The well-known fundamental metallicity relation which describes a close and tight relationship between metallicity and SFR (at fixed stellar mass) is therefore entirely a by-product of the underlying physical relationship with molecular gas mass (through the Schmidt-Kennicutt relation).
  • ItemAccepted versionOpen Access
    Detection of faint broad emission lines in type 2 AGN - II. On the measurement of the black hole mass of type 2 AGN and the unified model
    (Oxford University Press (OUP), 2017-06) Onori, F; Ricci, F; La Franca, F; Bianchi, S; Bongiorno, A; Brusa, M; Fiore, F; Maiolino, R; Marconi, A; Sani, E; Vignali, C; Maiolino, Roberto [0000-0002-4985-3819]
    © 2017 The Authors. We report the virial measurements of the black hole (BH) mass of a sample of 17 type 2 active galactic nuclei (AGN), drawn from the Swift/BAT 70-month 14-195 keVhard X-ray catalogue, where a faint BLR component has been measured via deep NIR (0.8-2.5 μm) spectroscopy. We compared the type 2 AGN with a control sample of 33 type 1 AGN. We find that the type 2 AGN BH masses span the 5 < log(MBH/M⊙) < 7.5 range, with an average log(MBH/M⊙) = 6.7, which is ~0.8 dex smaller than found for type 1 AGN. If type 1 and type 2 AGN of the same X-ray luminosity log(L14-195/erg s-1) ~ 43.5 are compared, type 2 AGN have 0.5 dex smaller BH masses than type 1 AGN. Although based on few tens of objects, this result disagrees with the standard AGN unification scenarios in which type 1 and type 2 AGN are the same objects observed along different viewing angles with respect to a toroidal absorbing material.
  • ItemAccepted versionOpen Access
    Physical Properties of the First Quasars
    (Cambridge University Press (CUP), 2017) Gallerani, S; Fan, X; Maiolino, R; Pacucci, F; Gallerani, S [0000-0002-7200-8293]
    Since the beginning of the new millennium, more than 100 $z\sim 6$ quasars have been discovered through several surveys and followed-up with multi-wavelength observations. These data provided a large amount of information on the growth of supermassive black holes at the early epochs, the properties of quasar host galaxies and the joint formation and evolution of these massive systems. We review the properties of the highest-$z$ quasars known so far, especially focusing on some of the most recent results obtained in (sub-)millimeter bands. We discuss key observational challenges and open issues in theoretical models and highlight possible new strategies to improve our understanding of the galaxy-black hole formation and evolution in the early Universe.
  • ItemAccepted versionOpen Access
    SDSS-IV MaNGA: Spatially resolved star formation histories in galaxies as a function of galaxy mass and type
    (Oxford University Press (OUP), 2017-05) Goddard, D; Thomas, D; Maraston, C; Westfall, K; Etherington, J; Riffel, R; Mallmann, ND; Zheng, Z; Argudo-Fernández, M; Lian, J; Bershady, M; Bundy, K; Drory, N; Law, D; Yan, R; Wake, D; Weijmans, A; Bizyaev, D; Brownstein, J; Lane, RR; Maiolino, R; Masters, K; Merrifield, M; Nitschelm, C; Pan, K; Roman-Lopes, A; Storchi-Bergmann, T; Schneider, DP; Maiolino, Roberto [0000-0002-4985-3819]
    © 2016 The Authors. We study the internal gradients of stellar population propertieswithin 1.5 Re for a representative sample of 721 galaxies, with stellar masses ranging between 109M⊙ and 1011.5M⊙ from the SDSS-IV MaNGA Integral-Field-Unit survey. Through the use of our full spectral fitting code FIREFLY, we derive light- and mass-weighted stellar population properties and their radial gradients, as well as full star formation and metal enrichment histories. We also quantify the impact that different stellar population models and full spectral fitting routines have on the derived stellar population properties and the radial gradient measurements. In our analysis, we find that age gradients tend to be shallow for both early-type and late-type galaxies. Mass-weighted age gradients of early-types arepositive (~0.09 dex/Re) pointing to 'outside- in' progression of star formation, while late-type galaxies have negative light-weighted age gradients (~-0.11 dex/Re), suggesting an 'inside-out' formation of discs. We detect negative metallicity gradients in both early- and late-type galaxies, but these are significantly steeper in late-types, suggesting that the radial dependence of chemical enrichment processes and the effect of gas inflow and metal transport are far more pronounced in discs. Metallicity gradients of both morphological classes correlate with galaxy mass, with negative metallicity gradients becoming steeper with increasing galaxy mass. The correlation with mass is stronger for late-type galaxies, with a slope of d(∇[Z/H])/d(logM) ~ -0.2 ± 0.05, compared to d(∇[Z/H])/d(logM) ~ -0.05 ± 0.05 for early-types. This result suggests that the merger history plays a relatively small role in shaping metallicity gradients of galaxies.
  • ItemPublished versionOpen Access
    Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
    (American Astronomical Society, 2017) Blanton, MR; Bershady, MA; Abolfathi, B; Albareti, FD; Prieto, CA; Almeida, A; Alonso-García, J; Anders, F; Anderson, SF; Andrews, B; Aquino-Ortíz, E; Aragón-Salamanca, A; Argudo-Fernández, M; Armengaud, E; Aubourg, E; Avila-Reese, V; Badenes, C; Bailey, S; Barger, KA; Barrera-Ballesteros, J; Bartosz, C; Bates, D; Baumgarten, F; Bautista, J; Beaton, R; Beers, TC; Belfiore, F; Bender, CF; Berlind, AA; Bernardi, M; Beutler, F; Bird, JC; Bizyaev, D; Blanc, GA; Blomqvist, M; Bolton, AS; Boquien, M; Borissova, J; Bosch, RVD; Bovy, J; Brandt, WN; Brinkmann, J; Brownstein, JR; Bundy, K; Burgasser, AJ; Burtin, E; Busca, NG; Cappellari, M; Carigi, MLD; Carlberg, JK; Rosell, AC; Carrera, R; Chanover, NJ; Cherinka, B; Cheung, E; Chew, YGM; Chiappini, C; Choi, PD; Chojnowski, D; Chuang, CH; Chung, H; Cirolini, RF; Clerc, N; Cohen, RE; Comparat, J; Costa, LD; Cousinou, MC; Covey, K; Crane, JD; Croft, RAC; Cruz-Gonzalez, I; Cuadra, DG; Cunha, K; Damke, GJ; Darling, J; Davies, R; Dawson, K; Macorra, ADL; Dell'Agli, F; Lee, ND; Delubac, T; Mille, FD; Diamond-Stanic, A; Cano-Díaz, M; Donor, J; Downes, JJ; Drory, N; Bourboux, HDMD; Duckworth, CJ; Dwelly, T; Dyer, J; Ebelke, G; Eigenbrot, AD; Eisenstein, DJ; Emsellem, E; Eracleous, M; Escoffier, S; Evans, ML; Fan, X; Fernández-Alvar, E; Blanton, MR [0000-0003-1641-6222]; Bershady, MA [0000-0002-3131-4374]; Prieto, CA [0000-0002-0084-572X]; Alonso-García, J [0000-0003-3496-3772]; Andrews, B [0000-0001-8085-5890]; Aragón-Salamanca, A [0000-0001-8215-1256]; Badenes, C [0000-0003-3494-343X]; Barger, KA [0000-0001-5817-0932]; Barrera-Ballesteros, J [0000-0003-2405-7258]; Beaton, R [0000-0002-1691-8217]; Beers, TC [0000-0003-4573-6233]; Bender, CF [0000-0003-4384-7220]; Berlind, AA [0000-0002-1814-2002]; Bizyaev, D [0000-0002-3601-133X]; Bosch, RVD [0000-0002-0420-6159]; Bovy, J [0000-0001-6855-442X]; Brandt, WN [0000-0002-0167-2453]; Brownstein, JR [0000-0002-8725-1069]; Bundy, K [0000-0001-9742-3138]; Burgasser, AJ [0000-0002-6523-9536]; Cappellari, M [0000-0002-1283-8420]; Carlberg, JK [0000-0001-5926-4471]; Rosell, AC [0000-0003-3044-5150]; Carrera, R [0000-0001-6143-8151]; Cheung, E [0000-0001-8546-1428]; Chojnowski, D [0000-0001-9984-0891]; Chung, H [0000-0002-3043-2555]; Covey, K [0000-0001-6914-7797]; Crane, JD [0000-0002-5226-787X]; Darling, J [0000-0003-2511-2060]; Davies, R [0000-0001-7897-3812]; Dawson, K [0000-0002-0553-3805]; Lee, ND [0000-0002-3657-0705]; Cano-Díaz, M [0000-0001-9553-8230]; Drory, N [0000-0002-7339-3170]; Eigenbrot, AD [0000-0003-0810-4368]; Emsellem, E [0000-0002-6155-7166]; Eracleous, M [0000-0002-3719-940X]; Fan, X [0000-0003-3310-0131]
    We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratio in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially-resolved spectroscopy for thousands of nearby galaxies (median redshift of z = 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between redshifts z = 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGN and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5-meter Sloan Foundation Telescope at Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5-meter du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in July 2016.
  • ItemAccepted versionOpen Access
    Physical conditions of the molecular gas in metal-poor galaxies
    (EDP Sciences, 2017) Hunt, LK; Weiß, A; Henkel, C; Combes, F; Garciá-Burillo, S; Casasola, V; Caselli, P; Lundgren, A; Maiolino, R; Menten, KM; Testi, L; Hunt, LK [0000-0001-9162-2371]
    Studying the molecular component of the interstellar medium in metal-poor galaxies has been challenging because of the faintness of carbon monoxide emission, the most common proxy of H2. Here we present new detections of molecular gas at low metallicities, and assess the physical conditions in the gas through various CO transitions for 8 galaxies. For one, NGC 1140 (Z/Zsun ~ 0.3), two detections of 13CO isotopologues and atomic carbon, [CI](1-0), and an upper limit for HCN(1-0) are also reported. After correcting to a common beam size, we compared 12CO(2-1)/12CO(1-0) (R21) and 12CO(3-2)/12CO(1-0) (R31) line ratios of our sample with galaxies from the literature and find that only NGC 1140 shows extreme values (R21 ~ R31 ~ 2). Fitting physical models to the 12CO and 13CO emission in NGC 1140 suggests that the molecular gas is cool (kinetic temperature Tkin<=20 K), dense (H2 volume density nH2 >= $10^6$ cm$^{-3}$), with moderate CO column density (NCO ~ $10^{16}$ cm$^{-2}$) and low filling factor. Surprisingly, the [12CO]/[13CO] abundance ratio in NGC 1140 is very low (~ 8-20), lower even than the value of 24 found in the Galactic Center. The young age of the starburst in NGC 1140 precludes 13C enrichment from evolved intermediate-mass stars; instead we attribute the low ratio to charge-exchange reactions and fractionation, because of the enhanced efficiency of these processes in cool gas at moderate column densities. Fitting physical models to 12CO and [CI](1-0) emission in NGC 1140 gives an unusually low [12CO]/[12C] abundance ratio, suggesting that in this galaxy atomic carbon is at least 10 times more abundant than 12CO.
  • ItemAccepted versionOpen Access
    On the discovery of fast molecular gas in the UFO/BAL quasar APM 08279+5255 at z = 3.912
    (EDP Sciences, 2017) Feruglio, C; Ferrara, A; Bischetti, M; Downes, D; Neri, R; Ceccarelli, C; Cicone, C; Fiore, F; Gallerani, S; Maiolino, R; Menci, N; Piconcelli, E; Vietri, G; Vignali, C; Zappacosta, L; Maiolino, Roberto [0000-0002-4985-3819]
    We have performed a high sensitivity observation of the UFO/BAL quasar APM 08279+5255 at z=3.912 with NOEMA at 3.2 mm, aimed at detecting fast moving molecular gas. We report the detection of blueshifted CO(4-3) with maximum velocity (v95\%) of $-1340$ km s$^{-1}$, with respect to the systemic peak emission, and a luminosity of $L' = 9.9\times 10^9 ~\mu^{-1}$ K km s$^{-1}$ pc$^{-2}$ (where $\mu$ is the lensing magnification factor). We discuss various scenarios for the nature of this emission, and conclude that this is the first detection of fast molecular gas at redshift $>3$. We derive a mass flow rate of molecular gas in the range $\rm \dot M=3-7.4\times 10^3$ M$_\odot$/yr, and momentum boost $\dot P_{OF} / \dot P_{AGN} \sim 2-6$, therefore consistent with a momentum conserving flow. For the largest $\dot P_{OF}$ the scaling is also consistent with a energy conserving flow with an efficiency of $\sim$10-20\%. The present data can hardly discriminate between the two expansion modes. The mass loading factor of the molecular outflow $\eta=\dot M_{OF}/SFR$ is $>>1$. We also detect a molecular emission line at a frequency of 94.83 GHz, corresponding to a rest frame frequency of 465.8 GHz, which we tentatively identified with the cation molecule $\rm N_2H^+$(5-4), which would be the first detection of this species at high redshift. We discuss the alternative possibility that this emission is due to a CO emission line from the, so far undetected, lens galaxy. Further observations of additional transitions of the same species with NOEMA can discriminate between the two scenarios.
  • ItemAccepted versionOpen Access
    The 13th Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey Mapping Nearby Galaxies at Apache Point Observatory
    (American Astronomical Society, 2017-12-01) Albareti, FD; Prieto, CA; Almeida, A; Anders, F; Anderson, S; Andrews, BH; Aragón-Salamanca, A; Argudo-Fernández, M; Armengaud, E; Aubourg, E; Avila-Reese, V; Badenes, C; Bailey, S; Barbuy, B; Barger, K; Barrera-Ballesteros, J; Bartosz, C; Basu, S; Bates, D; Battaglia, G; Baumgarten, F; Baur, J; Bautista, J; Beers, TC; Belfiore, F; Bershady, M; De Lis, SB; Bird, JC; Bizyaev, D; Blanc, GA; Blanton, M; Blomqvist, M; Bolton, AS; Borissova, J; Bovy, J; Brandt, WN; Brinkmann, J; Brownstein, JR; Bundy, K; Burtin, E; Busca, NG; Chavez, HOC; Diaz, MC; Cappellari, M; Carrera, R; Chen, Y; Cherinka, B; Cheung, E; Chiappini, C; Chojnowski, D; Chuang, CH; Chung, H; Cirolini, RF; Clerc, N; Cohen, RE; Comerford, JM; Comparat, J; Correa Do Nascimento, J; Cousinou, MC; Covey, K; Crane, JD; Croft, R; Cunha, K; Darling, J; Davidson, JW; Dawson, K; Da Costa, L; Da Silva Ilha, G; Machado, AD; Delubac, T; De Lee, N; De La Macorra, A; De La Torre, S; Diamond-Stanic, AM; Donor, J; Downes, JJ; Drory, N; Du, C; Du Mas Des Bourboux, H; Dwelly, T; Ebelke, G; Eigenbrot, A; Eisenstein, DJ; Elsworth, YP; Emsellem, E; Eracleous, M; Escoffier, S; Evans, ML; Falcón-Barroso, J; Fan, X; Favole, G; Fernandez-Alvar, E; Fernandez-Trincado, JG; Feuillet, D; Fleming, SW; Font-Ribera, A; Freischlad, G; Frinchaboy, P; Fu, H; Gao, Y
    The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) began observations in July 2014. It pursues three core programs: APOGEE-2, MaNGA, and eBOSS. In addition, eBOSS contains two major subprograms: TDSS and SPIDERS. This paper describes the first data release from SDSS-IV, Data Release 13 (DR13), which contains new data, reanalysis of existing data sets and, like all SDSS data releases, is inclusive of previously released data. DR13 makes publicly available 1390 spatially resolved integral field unit observations of nearby galaxies from MaNGA, the first data released from this survey. It includes new observations from eBOSS, completing SEQUELS. In addition to targeting galaxies and quasars, SEQUELS also targeted variability-selected objects from TDSS and X-ray selected objects from SPIDERS. DR13 includes new reductions of the SDSS-III BOSS data, improving the spectrophotometric calibration and redshift classification. DR13 releases new reductions of the APOGEE-1 data from SDSS-III, with abundances of elements not previously included and improved stellar parameters for dwarf stars and cooler stars. For the SDSS imaging data, DR13 provides new, more robust and precise photometric calibrations. Several value-added catalogs are being released in tandem with DR13, in particular target catalogs relevant for eBOSS, TDSS, and SPIDERS, and an updated red-clump catalog for APOGEE. This paper describes the location and format of the data now publicly available, as well as providing references to the important technical papers that describe the targeting, observing, and data reduction. The SDSS website,, provides links to the data, tutorials and examples of data access, and extensive documentation of the reduction and analysis procedures. DR13 is the first of a scheduled set that will contain new data and analyses from the planned ~6-year operations of SDSS-IV.
  • ItemPublished versionOpen Access
    SHINING, A Survey of Far-infrared Lines in Nearby Galaxies. I. Survey Description, Observational Trends, and Line Diagnostics
    (IOP Publishing, 2018) Herrera-Camus, R; Sturm, E; Graciá-Carpio, J; Lutz, D; Contursi, A; Veilleux, S; Fischer, J; González-Alfonso, E; Poglitsch, A; Tacconi, L; Genzel, R; Maiolino, R; Sternberg, A; Davies, R; Verma, A; Maiolino, Roberto [0000-0002-4985-3819]
    We use the Herschel/PACS spectrometer to study the global and spatially resolved far-infrared (FIR) fine-structure line emission in a sample of 52 galaxies that constitute the SHINING survey. These galaxies include star-forming, active-galactic nuclei (AGN), and luminous infrared galaxies (LIRGs). We find an increasing number of galaxies (and kiloparsec size regions within galaxies) with low line-to-FIR continuum ratios as a function of increasing FIR luminosity ($L_{\mathrm{FIR}}$), dust infrared color, $L_{\mathrm{FIR}}$ to molecular gas mass ratio ($L_{\mathrm{FIR}}/M_{\mathrm{mol}}$), and FIR surface brightness ($\Sigma_{\mathrm{FIR}}$). The correlations between the [CII]/FIR or [OI]/FIR ratios with $\Sigma_{\mathrm{FIR}}$ are remarkably tight ($\sim0.3$ dex scatter over almost four orders of magnitude in $\Sigma_{\mathrm{FIR}}$). We observe that galaxies with $L_{\mathrm{FIR}}/M_{\mathrm{mol}} \gtrsim 80\,L_{\odot}\,M_{\odot}^{-1}$ and $\Sigma_{\mathrm{FIR}}\gtrsim10^{11}$ $L_{\odot}$ kpc$^{-2}$ tend to have weak fine-structure line-to-FIR continuum ratios, and that LIRGs with infrared sizes $\gtrsim1$ kpc have line-to-FIR ratios comparable to those observed in typical star-forming galaxies. We analyze the physical mechanisms driving these trends in Paper II (Herrera-Camus et al. 2018). The combined analysis of the [CII], [NII], and [OIII] lines reveals that the fraction of the [CII] line emission that arises from neutral gas increases from 60% to 90% in the most active star-forming regions and that the emission originating in the ionized gas is associated with low-ionization, diffuse gas rather than with dense gas in HII regions. Finally, we report the global and spatially resolved line fluxes of the SHINING galaxies to enable the comparison and planning of future local and high-$z$ studies.
  • ItemPublished versionOpen Access
    SHINING, A Survey of Far-infrared Lines in Nearby Galaxies. II. Line-deficit Models, AGN Impact, [C II]–SFR Scaling Relations, and Mass–Metallicity Relation in (U)LIRGs
    (IOP Publishing, 2018) Herrera-Camus, R; Sturm, E; Graciá-Carpio, J; Lutz, D; Contursi, A; Veilleux, S; Fischer, J; González-Alfonso, E; Poglitsch, A; Tacconi, L; Genzel, R; Maiolino, R; Sternberg, A; Davies, R; Verma, A; Maiolino, Roberto [0000-0002-4985-3819]
    The SHINING survey (Paper I; Herrera-Camus et al. 2018) offers a great opportunity to study the properties of the ionized and neutral media of galaxies from prototypical starbursts and active galactic nuclei (AGN) to heavily obscured objects. Based on Herschel/PACS observations of the main far-infrared (FIR) fine-structure lines, in this paper we analyze the physical mechanisms behind the observed line deficits in galaxies, the apparent offset of luminous infrared galaxies (LIRGs) from the mass-metallicity relation, and the scaling relations between [CII] 158 $\mu$m line emission and star formation rate (SFR). Based on a toy model and the Cloudy code, we conclude that the increase in the ionization parameter with FIR surface brightness can explain the observed decrease in the line-to-FIR continuum ratio of galaxies. In the case of the [CII] line, the increase in the ionization parameter is accompanied by a reduction in the photoelectric heating efficiency and the inability of the line to track the increase in the FUV radiation field as galaxies become more compact and luminous. In the central $\sim$kiloparsec regions of AGN galaxies we observe a significant increase in the [OI] 63 $\mu$m/[CII] line ratio; the AGN impact on the line-to-FIR ratios fades on global scales. Based on extinction-insensitive metallicity measurements of LIRGs we confirm that they lie below the mass-metallicity relation, but the offset is smaller than those reported in studies that use optical-based metal abundances. Finally, we present scaling relations between [CII] emission and SFR in the context of the main-sequence of star-forming galaxies.
  • ItemAccepted versionOpen Access
    Dissipative structures in magnetorotational turbulence
    (Oxford University Press (OUP), 2018) Ross, J; Latter, HN
    Via the process of accretion, magnetorotational turbulence removes energy from a disk's orbital motion and transforms it into heat. Turbulent heating is far from uniform and is usually concentrated in small regions of intense dissipation, characterised by abrupt magnetic reconnection and higher temperatures. These regions are of interest because they might generate non-thermal emission, in the form of flares and energetic particles, or thermally process solids in protoplanetary disks. Moreover, the nature of the dissipation bears on the fundamental dynamics of the magnetorotational instability (MRI) itself: local simulations indicate that the large-scale properties of the turbulence (e.g. saturation levels, the stress-pressure relationship) depend on the short dissipative scales. In this paper we undertake a numerical study of how the MRI dissipates and the small-scale dissipative structures it employs to do so. We use the Godunov code RAMSES and unstratified compressible shearing boxes. Our simulations reveal that dissipation is concentrated in ribbons of strong magnetic reconnection that are significantly elongated in azimuth, up to a scale height. Dissipative structures are hence meso-scale objects, and potentially provide a route by which large scales and small scales interact. We go on to show how these ribbons evolve over time --- forming, merging, breaking apart, and disappearing. Finally, we reveal important couplings between the large-scale density waves generated by the MRI and the small-scale structures, which may illuminate the stress-pressure relationship in MRI turbulence.