arXiv subjects

A. Ferrara

Publications and source records attributed to A. Ferrara.

At least 109 records · Page 6Linked to original sources

arXiv2019

Populations behind the source-subtracted cosmic infrared background anisotropies

While the upcoming telescopes will reveal correspondingly fainter, more distant galaxies, a question will persist: what more is there that these telescopes cannot see? One answer is the source-subtracted Cosmic Infrared Background (CIB). The CIB is comprised of the collective light from all sources remaining after known, resolved sources are accounted for. Ever-more-sensitive surveys will identify the brightest of these, allowing them to be removed, and - like peeling layers off an onion - reveal deeper layers of the CIB. In this way it is possible to measure the contributions from populations not accessible to direct telescopic observation. Measurement of fluctuations in the source-subtracted CIB, i.e., the spatial power spectrum of the CIB after subtracting resolved sources, provides a robust means of characterizing its faint, and potentially new, populations. Studies over the past 15 years have revealed source-subtracted CIB fluctuations on scales out to ~100' which cannot be explained by extrapolating from known galaxy populations. Moreover, they appear highly coherent with the unresolved Cosmic X-ray Background, hinting at a significant population of accreting black holes among the CIB sources. Characterizing the source-subtracted CIB with high accuracy, and thereby constraining the nature of the new populations, is feasible with upcoming instruments and would produce critically important cosmological information in the next decade. New coextensive deep and wide-area near-infrared, X-ray, and microwave surveys will bring decisive opportunities to examine, with high fidelity, the spatial spectrum and origin of the CIB fluctuations and their cross-correlations with cosmic microwave and X-ray backgrounds, and determine the formation epochs and the nature of the new sources (stellar nucleosynthetic or accreting black holes).

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arXiv2018

Witnessing galaxy assembly at the edge of the reionization epoch

We report the discovery of Serenity-18, a galaxy at z=5.939 for which we could measure the content of molecular gas, M(H_2)~ 5 x10^9 M_sun, traced by the CO(6-5) emission, together with the metal-poor ([Fe/H]=-3.08 +- 0.12, [Si/H]=-2.86 +- 0.14) gas clump/filament which is possibly feeding its growth. The galaxy has an estimated star formation rate of ~100 M_sun yr^{-1}, implying that it is a typical main sequence galaxy at these redshifts. The metal-poor gas is detected through a damped Lyman-alpha absorber (DLA) observed at a spatial separation of 40 kpc and at the same redshift of Serenity-18, along the line of sight to the quasar SDSS J2310+1855 (z_em = 6.0025). The chemical abundances measured for the damped Lyman-alpha system are in very good agreement with those measured for other DLAs discovered at similar redshifts, indicating an enrichment due to massive PopII stars. The galaxy/Damped system we discovered is a direct observational evidence of the assembly of a galaxy at the edge of the reionization epoch.

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arXiv2018

Science with an ngVLA: [CII] 158$μ$m Emission from $z \ge 10$ Galaxies

We consider the capabilities of ALMA and the ngVLA to detect and image the[CII] 158\,$μ$m line from galaxies into the cosmic `dark ages' ($z \sim 10$ to 20). The [CII] line may prove to be a powerful tool in determining spectroscopic redshifts, and galaxy dynamics, for the first galaxies. In 40\,hr, ALMA has the sensitivity to detect the integrated [CII] line emission from a moderate metallicity, active star-forming galaxy [$Z_A = 0.2\,Z_{\odot}$; star formation rate (SFR)= 5\,$M_\odot$\,yr$^{-1}$], at $z = 10$ at a significance of 6$σ$. The ngVLA will detect the integrated [CII] line emission from a Milky-Way like star formation rate galaxy ($Z_{A} = 0.2\,Z_{\odot}$, SFR = 1\,$M_\odot$\,yr$^{-1}$), at $z = 15$ at a significance of 6$σ$. Imaging simulations show that the ngVLA can determine rotation dynamics for active star-forming galaxies at $z \sim 15$, if they exist. The [CII] detection rate in blind surveys will be slow (of order unity per 40\,hr pointing.

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arXiv2018

On the faint-end of the galaxy luminosity function in the Epoch of Reionization: updated constraints from the HST Frontier Fields

Ultra-faint galaxies are hosted by small dark matter halos with shallow gravitational potential wells, hence their star formation activity is more sensitive to feedback effects. The shape of the faint-end of the high-$z$ galaxy luminosity function (LF) contains important information on star formation and its interaction with the reionization process during the Epoch of Reionization (EoR). High-$z$ galaxies with $M_{\rm UV}\gtrsim-17$ have only recently become accessible thanks to the Frontier Fields (FFs) survey combining deep {\it HST} imaging and the gravitational lensing effect. In this paper we investigate the faint-end of the LF at redshift $>$5 using the data of FFs clusters Abell 2744 (A2744), MACSJ0416.1-2403 (M0416), MACSJ0717.5+3745 (M0717) and MACSJ1149.5+2223 (M1149). We analyze both an empirical and a physically-motivated LF model to obtain constraints on a possible turn-over of LF at faint magnitudes. In the empirical model the LF drops fast when the absolute UV magnitude $M_{\rm UV}$ is much larger than a turn-over absolute UV magnitude $M_{\rm UV}^{\rm T}$. We obtain $M_{\rm UV}^{\rm T}\gtrsim-14.6 $ (15.2) at 1 (2) $σ$ confidence level (C.L.) for $z\sim6$. In the physically-motivated analytical model, star formation in halos with circular velocity below $v_c^*$ is fully quenched if these halos are located in ionized regions. Using updated lensing models and new additional FFs data, we re-analyze previous constraints on $v_c^*$ and $f_{\rm esc}$ presented by Castellano et al. 2016a (C16a) using a smaller dataset. We obtain new constraints on $v_c^*\lesssim 59$ km s$^{-1}$ and $f_{\rm esc}\lesssim 56\%$ (both at 2$σ$ C.L.) and conclude that there is no turn-over detected so far from the analyzed FFs data. Forthcoming {\it JWST} observations will be key to tight these constraints further.

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arXiv2018

Probing the High-Redshift Universe with SPICA: Toward the Epoch of Reionization and Beyond

With the recent discovery of a dozen dusty star-forming galaxies and around 30 quasars at z>5 that are hyper-luminous in the infrared ($μ$$L_{\rm IR}>10^{13}$ L$_{\odot}$, where $μ$ is a lensing magnification factor), the possibility has opened up for SPICA, the proposed ESA M5 mid-/far-infrared mission, to extend its spectroscopic studies toward the epoch of reionization and beyond. In this paper, we examine the feasibility and scientific potential of such observations with SPICA's far-infrared spectrometer SAFARI, which will probe a spectral range (35-230 $μ$m) that will be unexplored by ALMA and JWST. Our simulations show that SAFARI is capable of delivering good-quality spectra for hyper-luminous infrared galaxies (HyLIRGs) at z=5-10, allowing us to sample spectral features in the rest-frame mid-infrared and to investigate a host of key scientific issues, such as the relative importance of star formation versus AGN, the hardness of the radiation field, the level of chemical enrichment, and the properties of the molecular gas. From a broader perspective, SAFARI offers the potential to open up a new frontier in the study of the early Universe, providing access to uniquely powerful spectral features for probing first-generation objects, such as the key cooling lines of low-metallicity or metal-free forming galaxies (fine-structure and H2 lines) and emission features of solid compounds freshly synthesized by Population III supernovae. Ultimately, SAFARI's ability to explore the high-redshift Universe will be determined by the availability of sufficiently bright targets (whether intrinsically luminous or gravitationally lensed). With its launch expected around 2030, SPICA is ideally positioned to take full advantage of upcoming wide-field surveys such as LSST, SKA, Euclid, and WFIRST, which are likely to provide extraordinary targets for SAFARI.

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arXiv2018

The dense molecular gas in the $\rm z\sim6$ QSO SDSS J231038.88+185519.7 resolved by ALMA

We present ALMA observations of the CO(6-5) and [CII] emission lines and the sub-millimeter continuum of the $z\sim6$ quasi-stellar object (QSO) SDSS J231038.88+185519.7. Compared to previous studies, we have analyzed a synthetic beam that is ten times smaller in angular size, we have achieved ten times better sensitivity in the CO(6-5) line, and two and half times better sensitivity in the [CII] line, enabling us to resolve the molecular gas emission. We obtain a size of the dense molecular gas of $2.9\pm0.5$ kpc, and of $1.4\pm0.2$ kpc for the 91.5 GHz dust continuum. By assuming that CO(6-5) is thermalized, and by adopting a CO--to--$H_2$ conversion factor $\rm α_{CO} = 0.8~ M_{\odot}~K^{-1}~ (km/s)^{-1} ~pc^{2}$, we infer a molecular gas mass of $\rm M(H_2)=(3.2 \pm0.2) \times 10^{10}\rm M_{\odot}$. Assuming that the observed CO velocity gradient is due to an inclined rotating disk, we derive a dynamical mass of $\rm M_{dyn}~sin^2(i) = (2.4\pm0.5) \times 10^{10}~ M_{\odot}$, which is a factor of approximately two smaller than the previously reported estimate based on [CII]. Regarding the central black hole, we provide a new estimate of the black hole mass based on the C~IV emission line detected in the X-SHOOTER/VLT spectrum: $\rm M_{BH}=(1.8\pm 0.5) \times 10^{9}~ M_{\odot}$. We find a molecular gas fraction of $\rm μ=M(H_2)/M^*\sim4.4$, where $\rm M^*\approx M_{dyn} - M(H_2)-M(BH)$. We derive a ratio $v_{rot}/σ\approx 1-2$ suggesting high gas turbulence, outflows/inflows and/or complex kinematics due to a merger event. We estimate a global Toomre parameter $Q\sim 0.2-0.5$, indicating likely cloud fragmentation. We compare, at the same angular resolution, the CO(6-5) and [CII] distributions, finding that dense molecular gas is more centrally concentrated with respect to [CII]. We find that the current BH growth rate is similar to that of its host galaxy.

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arXiv2018

Spectroscopic investigation of a reionized galaxy overdensity at z=7

We present deep spectroscopic follow-up observations of the Bremer Deep Field (BDF) where the two $z\sim$7 bright Ly$α$ emitters (LAE) BDF521 and BDF3299 were previously discovered by Vanzella et al. (2011) and where a factor of $\sim$3-4 overdensity of faint LBGs has been found by Castellano et al. (2016). We confirm a new bright Ly$α$ emitter, BDF2195, at the same redshift of BDF521, $z=7.008$, and at only $\sim$90 kpc physical distance from it, confirming that the BDF area is likely an overdense, reionized region. A quantitative assessment of the Ly$α$ fraction shows that the number of detected bright emitters is much higher than the average found at z$\sim$7, suggesting a high Ly$α$ transmission through the inter-galactic medium (IGM). However, the line visibility from fainter galaxies is at odds with this finding, since no Ly$α$ emission is found in any of the observed candidates with $M_{UV}>$-20.25. This discrepancy can be understood either if some mechanism prevents Ly$α$ emission from fainter galaxies within the ionized bubbles from reaching the observer, or if faint galaxies are located outside the reionized area and bright LAEs are solely responsible for the creation of their own HII regions. A thorough assessment of the nature of the BDF region and of its sources of re-ionizing radiation will be made possible by JWST spectroscopic capabilities.

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arXiv2018

The THESEUS space mission concept: science case, design and expected performances

THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRB and X-ray transient detection over a broad field of view (more than 1sr) with 0.5-1 arcmin localization, an energy band extending from several MeV down to 0.3 keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) follow-up with a 0.7 m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing the main open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the inter-stellar and intra-galactic medium up to redshift $\sim$10, signatures of Pop III stars, sources and physics of re-ionization, and the faint end of the galaxy luminosity function. In addition, it will provide unprecedented capability to monitor the X-ray variable sky, thus detecting, localizing, and identifying the electromagnetic counterparts to sources of gravitational radiation, which may be routinely detected in the late '20s / early '30s by next generation facilities like aLIGO/ aVirgo, eLISA, KAGRA, and Einstein Telescope. THESEUS will also provide powerful synergies with the next generation of multi-wavelength observatories (e.g., LSST, ELT, SKA, CTA, ATHENA).

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arXiv2018

Dusty galaxies in the Epoch of Reionization: simulations

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. 2017}). 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(2017), i.e. a star formation rate of $\mathrm{SFR} = 78\;\rm M_\odot \rm yr^{-1}$, a factor $\approx 4$ higher than deduced from simple Spectral Energy Distribution fitting. In this case we find: (a) dust attenuation (corresponding to $τ_V=1.4$) is consistent with a Milky Way extinction curve; (b) the dust-to-metal ratio is low, $f_\mathrm{d} \sim 0.08$, implying that early dust formation is rather inefficient; (c) the luminosity-weighted dust temperature is high, $T_d=91\pm 23\, \rm K$, as a result of the intense ($\approx 100\times$ MW) interstellar radiation field; (d) due to the high $T_d$, the ALMA Band 7 detection can be explained by a limited dust mass, $M_d=1.6\times 10^6 $M$_\odot$. Finally, the high dust temperatures might solve the puzzling low infrared excess recently deduced for high-$z$ galaxies from the IRX-$β$ relation.

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arXiv2018

Looking at cosmic near-infrared background radiation anisotropies

The cosmic infrared background (CIB) contains emissions accumulated over the entire history of the Universe, including from objects inaccessible to individual telescopic studies. The near-IR (~1-10 mic) part of the CIB, and its fluctuations, reflects emissions from nucleosynthetic sources and gravitationally accreting black holes (BHs). If known galaxies are removed to sufficient depths the source-subtracted CIB fluctuations at near-IR can reveal sources present in the first-stars-era and possibly new stellar populations at more recent times. This review discusses the recent progress in this newly emerging field which identified, with new data and methodology, significant source-subtracted CIB fluctuations substantially in excess of what can be produced by remaining known galaxies. The CIB fluctuations further appear coherent with unresolved cosmic X-ray background (CXB) indicating a very high fraction of BHs among the new sources producing the CIB fluctuations. These observations have led to intensive theoretical efforts to explain the measurements and their properties. While current experimental configurations have limitations in decisively probing these theories, their potentially remarkable implications will be tested in the upcoming CIB measurements with the ESA's Euclid dark energy mission. We describe the goals and methodologies of LIBRAE (Looking at Infrared Background Radiation with Euclid), a NASA-selected project for CIB science with Euclid, which has the potential for transforming the field into a new area of precision cosmology.

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arXiv2018

First Stars, Reionization and Gamma-Ray Bursts

Gamma-Ray Bursts represent unique tools to study the early phases of cosmic evolution, the formation of the first stars and galaxies. Absorption line spectra of these sources located in the Epoch of Reionization might provide us with key information about these remote, and yet fundamental, stages of cosmic history. I will briefly review these issues, highlighting the immense leap that the Þmission could represent for finding answers to the many fundamental open questions.

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arXiv2017

ALMA suggests outflows in z~5.5 galaxies

We present the first attempt to detect outflows from galaxies approaching the Epoch of Reionization (EoR) using a sample of 9 star-forming ($\rm SFR=31\pm 20~M_{\odot}~yr^{-1}$) $z\sim 5.5$ galaxies for which the [CII]158$μ$m line has been previously obtained with 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 characterised by a flux excess of $\sim 0.5$ mJy extended over $\sim 1000$ 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 [CII] lines, signatures of starburst-driven outflows. We infer an average outflow rate of $\rm \dot{M}=54\pm23~ M_{\odot}~yr^{-1}$, providing a loading factor $η=\rm \dot{M}/SFR=1.7\pm1.3$ in agreement with observed local starbursts. Our interpretation is consistent with outcomes from zoomed hydro-simulations of {\it Dahlia}, a $z\sim 6$ galaxy ($\rm SFR\sim 100~\rm M_{\odot}~yr^{-1}$) whose feedback-regulated star formation results into an outflow rate $\rm \dot{M}\sim 30~ M_{\odot}~yr^{-1}$. The quality of the ALMA data is not sufficient for a detailed analysis of the [CII] 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 [CII] line in this sample are required to better characterise feedback at high-$z$ and to understand the role of outflows in shaping early galaxy formation.

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arXiv2017

Measuring patchy reionisation with kSZ$^2$-21 cm correlations

We study cross-correlations of the kinetic Sunyaev-Zel'dovich effect (kSZ) and 21 cm signals during the epoch of reionisation (EoR) to measure the effects of patchy reionisation. Since the kSZ effect is proportional to the line-of-sight velocity, the kSZ-21 cm cross correlation suffers from cancellation at small angular scales. We thus focus on the correlation between the kSZ-squared field (kSZ$^2$) and 21 cm signals. When the global ionisation fraction is low ($x_e\lesssim 0.7$), the kSZ$^2$ fluctuation is dominated by rare ionised bubbles which leads to an anti-correlation with the 21 cm signal. When $0.8\lesssim x_e<1$, the correlation is dominated by small pockets of neutral regions, leading to a positive correlation. However, at very high redshifts when $x_e<0.15$, the spin temperature fluctuations change the sign of the correlation from negative to positive, as weakly ionised regions can have strong 21 cm signals in this case. To extract this correlation, we find that Wiener filtering is effective in removing large signals from the primary CMB anisotropy. The expected signal-to-noise ratios for a $\sim$10-hour integration of upcoming Square Kilometer Array data cross-correlated with maps from the current generation of CMB observatories with 3.4~$μ$K arcmin noise and 1.7~arcmin beam over 100~deg$^2$ are 51, 60, and 37 for $x_e=0.2$, 0.5, and 0.9, respectively.

astro-ph.CO↗

arXiv2017

Kiloparsec-scale gaseous clumps and star formation at $z=5-7$

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 $z\sim6-7$ 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$_{\rm [CII]}$-SFR relation at early epochs is fully consistent with the local relation, but it has a dispersion of 0.48$\pm$0.07 dex, which is about two times larger than observed locally. We also find that the deviation from the local L$_{\rm [CII]}$-SFR relation has a weak anti-correlation with the EW(Ly$α$). 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 ${\rm Σ_{[CII}-Σ_{SFR}}$ relation. These properties are likely a consequence of a combination of different effects, 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.

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arXiv2017

ALMA reveals metals yet no dust within multiple components in CR7

We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [CII]$_{158 μ\rm m}$ line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Ly$α$ emitting galaxy at $z=6.6$ that consists of three separated UV-continuum components. Our observations reveal several well-separated components of [CII] emission. The two most luminous components in [CII] coincide with the brightest UV components (A and B), blue-shifted by $\approx 150$ km s$^{-1}$ with respect to the peak of Ly$α$ emission. Other [CII] components are observed close to UV clumps B and C and are blue-shifted by $\approx300$ and $\approx80$ km s$^{-1}$ with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3$σ$ limiting luminosity L$_{\rm IR} (T_d = 35 \rm \, K) < 3.1\times10^{10}$ L$_{\odot}$. 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$_{\odot}$ yr$^{-1}$. All clumps have [CII] luminosities consistent within the scatter observed in the local relation between SFR and L$_{\rm [CII]}$, implying that strong Ly$α$ emission does not necessarily anti-correlate with [CII] luminosity. Combining our measurements with the literature, we show that galaxies with blue UV slopes have weaker [CII] emission at fixed SFR, potentially due to their lower metallicities and/or higher photoionisation. Comparison with hydrodynamical simulations suggests that CR7's clumps have metallicities of $0.1<\rm Z/Z_{\odot}<0.2$. 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.

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arXiv2017

Unbiased large spectroscopic surveys of galaxies selected by SPICA using dust bands

The mid-infrared (IR) range contains many spectral features associated with large molecules and dust grains such as polycyclic aromatic hydrocarbons (PAHs) and silicates. These are usually very strong compared to fine-structure gas lines, and thus valuable in studying the spectral properties of faint distant galaxies. In this paper, we evaluate the capability of low-resolution mid-IR spectroscopic surveys of galaxies that could be performed by SPICA. The surveys are designed to address the question how star formation and black hole accretion activities evolved over cosmic time through spectral diagnostics of the physical conditions of the interstellar/circumnuclear media in galaxies. On the basis of results obtained with Herschel far-IR photometric surveys of distant galaxies and Spitzer and AKARI near- to mid-IR spectroscopic observations of nearby galaxies, we estimate the numbers of the galaxies at redshift z > 0.5, which are expected to be detected in the PAH features or dust continuum by a wide (10 deg^2) or deep (1 deg^2) blind survey, both for a given observation time of 600 hours. As by-products of the wide blind survey, we also expect to detect debris disks, through the mid-IR excess above the photospheric emission of nearby main-sequence stars, and we estimate their number. We demonstrate that the SPICA mid-IR surveys will efficiently provide us with unprecedentedly large spectral samples, which can be studied further in the far-IR with SPICA.

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arXiv2017

Galaxy evolution studies with the SPace IR telescope for Cosmology and Astrophysics (SPICA): the power of IR spectroscopy

IR spectroscopy in the range 12-230 micron with the SPace IR telescope for Cosmology and Astrophysics (SPICA) will reveal the physical processes that govern the formation and evolution of galaxies and black holes through cosmic time, bridging the gap between the James Webb Space Telescope (JWST) and the new generation of Extremely Large Telescopes (ELTs) at shorter wavelengths and the Atacama Large Millimeter Array (ALMA) at longer wavelengths. SPICA, with its 2.5-m telescope actively-cooled to below 8K, 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 (AGN), sampling a large range in mass and luminosity, from faint local dwarf galaxies to luminous quasars in the distant Universe. AGN and starburst feedback and feeding mechanisms in distant galaxies will be uncovered through detailed measurements of molecular and atomic line profiles. 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~6. Furthermore, SPICA spectroscopy will uncover the most luminous galaxies in the first few hundred million years of the Universe, through their characteristic dust and molecular hydrogen features.

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arXiv2017

On the discovery of fast molecular gas in the UFO/BAL quasar APM 08279+5255 at z=3.912

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 $L' = 9.9\times 10^9 ~μ^{-1}$ K km s$^{-1}$ pc$^{-2}$ (where $μ$ 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 $η=\dot M_{OF}/SFR$ 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.

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