arXiv subjects

Michele Ginolfi

Publications and source records attributed to Michele Ginolfi.

49 records · Page 3Linked to original sources

arXiv2023

Bubbles and outflows: the novel JWST/NIRSpec view of the z=1.59 obscured quasar XID2028

Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, although direct observational evidence is still scarce and debated. Here we present Early Release Science JWST NIRSpec IFU observations of the z=1.59 prototypical obscured Active Galactic Nucleus (AGN) XID2028: This target represents a unique test case for studying quasar feedback at the peak epoch of AGN-galaxy co-evolution because extensive multi-wavelength coverage is available and a massive and extended outflow is detected in the ionised and molecular components. With the unprecedented sensitivity and spatial resolution of the JWST, the NIRSpec dataset reveals a wealth of structures in the ionised gas kinematics and morphology that were previously hidden in the seeing-limited ground-based data. In particular, we find evidence of an interaction between the interstellar medium of the galaxy and the quasar-driven outflow and radio jet that produces an expanding bubble from which the fast and extended wind detected in previous observations emerges. The new observations confirm the complex interplay between the AGN jet, wind and the interstellar medium of the host galaxy, highlighting the role of low-luminosity radio jets in AGN feedback. They also clearly show the new window that NIRSpec opens for detailed studies of feedback at high redshift.

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arXiv2023

A solar metallicity galaxy at $z >$ 7? Possible detection of the [N II] 122 $μ$m and [O III] 52 $μ$m lines

We present the first detection of the [N II] 122 $μ$m and [O III] 52 $μ$m lines for a reionisation-epoch galaxy. Based on these lines and previous [C II] 158 $μ$m and [O III] 88 $μ$m measurements, using two different radiative transfer models of the interstellar medium, we estimate an upper limit on electron density of $\lesssim$ 500 cm$^{-3}$ and a gas-phase metallicity $Z/Z_\odot \sim 1.1 \pm 0.2$ for A1689-zD1, a gravitationally-lensed, dusty galaxy at $z$ = 7.133. Other measurements or indicators of metallicity so far in galaxy interstellar media at $z \gtrsim$ 6 are typically an order of magnitude lower than this. The unusually high metallicity makes A1689-zD1 inconsistent with the fundamental metallicity relation, although there is likely significant dust obscuration of the stellar mass, which may partly resolve the inconsistency. Given a solar metallicity, the dust-to-metals ratio is a factor of several lower than expected, hinting that galaxies beyond $z \sim$ 7 may have lower dust formation efficiency. Finally, the inferred nitrogen enrichment compared to oxygen, on which the metallicity measurement depends, indicates that star-formation in the system is older than about 250 Myr, pushing the beginnings of this galaxy to $z >$ 10.

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arXiv2023

To see or not to see a $z\sim13$ galaxy, that is the question

Determining when the first galaxies formed remains an outstanding goal of modern observational astronomy. Theory and current stellar population models imply that the first galaxies formed at least at $z = 14-15$. But to date, only one galaxy at $z > 13$ (GS-z13-0) has been spectroscopically confirmed.. The galaxy `HD1' was recently proposed to be a z=13.27 galaxy based on its potential Lyman break and tentative [O III] 88 μm detection with ALMA. We hereby aim to test this scenario with new ALMA Band 4, DDT observations of what would be the [C II] 158 μm emission, if HD1 is at z$\sim$13.27. We carefully analyse the new ALMA Band 4 observations and re-analyse the existing ALMA Band 6 data on the source to determine the proposed redshift. We find a tentative $4σ$ feature in the Band 4 data that is spatially offset by 1.7" and spectrally offset by 190 km s-1 from the previously-reported $3.8σ$ `[O III] 88 μm' feature. Through various statistical tests, we demonstrate that these tentative features are fully consistent with both being random noise features. We conclude that we are more likely to be recovering noise features than both [O III] and [C II] emission from a source at $z\sim 13.27$. Although we find no credible evidence of a $z\sim 13.27$ galaxy, we cannot entirely rule out this scenario. Non-detections are also possible for a $z\sim 13$ source with a low interstellar gas-phase metallicity or ionisation parameter and/or high gas density. Determining where and exactly what type of galaxy HD1 is, will now likely require JWST/NIRSpec spectroscopy.

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arXiv2022

The ALPINE-ALMA [CII] survey: The infrared-radio correlation and AGN fraction of star-forming galaxies at z $\sim$ 4.4-5.9

We present the radio properties of 66 spectroscopically-confirmed normal star-forming galaxies (SFGs) at $4.4<z<5.9$ in the COSMOS field that were [C II] detected in the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [C II] at Early times (ALPINE). We separate these galaxies ("CII-detected-all") into lower redshift ("CII-detected-lz", $\langle z\rangle=4.5$) and higher redshift ("CII-detected-hz", $\langle z\rangle=5.6$) sub-samples and stack multi-wavelength imaging for each sub-sample from X-ray to radio bands. A radio signal is detected in the stacked 3 GHz image of CII-detected-all and -lz samples at $\gtrsim3σ$. We find that the infrared-radio correlation of our sample, quantified by $q_{\mathrm{TIR}}$, is lower than the local relation for normal SFGs at $\sim$3$σ$ significance level, and is instead broadly consistent with that of bright sub-mm galaxies at $2<z<5$. Neither of these samples show evidence of dominant AGN activity in their stacked Spectral Energy Distributions (SEDs), rest-frame UV spectra, or X-ray images. Although we cannot rule out the possible effect of the assumed spectral index and the applied infrared SED templates as at least partially causing these differences, the lower obscured fraction of star formation than at lower redshift can alleviate the tension between our stacked $q_{\mathrm{TIR}}$s and that of local normal SFGs. It is possible that the dust buildup, which primarily governs the IR emission in addition to older stellar populations, has not had enough time to occur fully in these galaxies, whereas the radio emission can respond on a more rapid timescale. Therefore, we might expect a lower $q_{\mathrm{TIR}}$ to be a general property of high-redshift SFGs.

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arXiv2022

The ALPINE-ALMA [CII] survey: dust attenuation curves at z=4.4-5.5

There is now ample evidence that dust is already present in abundance at high z. However, given the faintness of distant galaxies in the optical and the NIR, datasets are still limited and how the dust affects the emerging radiation of galaxies at very high redshift is not yet fully understood. Using the ALPINE survey, our objective is to quantify the dust attenuation properties in galaxies at z=4.4-5.5, and in particular the shape of their attenuation curve. Using the CIGALE code, we model the stellar populations and their interaction with the dust in order to measure some of the physical properties of a subsample of 23 main-sequence ALPINE galaxies. We find that the attenuation curves span a broad range of properties, from curves that are much steeper than the SMC extinction curve, to shallower than the starburst attenuation curve. The shape of the attenuation curves strongly depends on the V-band attenuation. Galaxies with the lowest attenuation also present the steepest curves. The steepness of such curves is probably the consequence of the combination of the intrinsic physical properties of the dust, the relative distribution of stars and dust in the interstellar medium, and the differential reddening. The broad range of attenuation curves found at z~5 shows that no single attenuation curve is appropriate for main sequence galaxies and that assuming a fixed curve can lead to large errors, for instance in the interpretation and use of the IRX-beta diagram, if SED modeling is not feasible. Great caution should be exercised when correcting high redshift galaxies for the presence of dust using the UV slope beta as it can affect the estimation of both SFR and stellar mass even at low V-band attenuation due to the steepness of the attenuation curve. However, when SED modeling can be used, the impact of the choice of the attenuation curve on the SFR and the stellar mass is limited.

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arXiv2020

Metal enrichment in the circumgalactic medium and Lyα haloes around quasars at z $\sim$3

Deep observations have detected extended Ly$α$ emission nebulae surrounding tens of quasars at redshift 2 to 6. However, the metallicity of such extended haloes is still poorly understood. We perform a detailed analysis on a large sample of 80 quasars at $z\sim3$ based on MUSE-VLT data. We find clear evidence of extended emission of the UV nebular lines such as CIV or HeII for about 20$\%$ of the sample, while CIII] is only marginally detected in a few objects. By stacking the cubes we detect emission of CIV, HeII and CIII] out to a radius of about 45 kpc. CIV and HeII show a radial decline much steeper than Ly$α$, while CIII] shows a shallower profile similar to Ly$α$ in the inner 45 kpc. We infer that the average metallicity of the circumgalactic gas within the central 30-50~kpc is $\sim$0.5 solar, or even higher. However, we also find evidence of a component of the Ly$α$ haloes, which has much weaker metal emission lines relative to Ly$α$. We suggest that the high metallicity of the circumgalactic medium within the central 30-50 kpc is associated with chemical pre-enrichment by past quasar-driven outflows and that there is a more extended component of the CGM that has much lower metallicity and likely associated with near-pristine gas accreted from the intergalactic medium. We show that our observational results are in good agreement with the expectations of the FABLE zoom-in cosmological simulations.

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arXiv2020

The ALPINE-ALMA [C II] survey: the luminosity function of serendipitous [C II] line emitters at $z\sim 5$

We present the first [CII] 158 $μ$m luminosity function (LF) at $z\sim 5$ from a sample of serendipitous lines detected in the ALMA Large Program to INvestigate [CII] at Early times (ALPINE). A search performed over the 118 ALPINE pointings revealed several serendipitous lines. Based on their fidelity, we selected 14 lines for the final catalog. According to the redshift of their counterparts, we identified 8 out of 14 detections as [CII] lines at $z\sim 5$, and two as CO transitions at lower redshifts. The remaining 4 lines have an elusive identification in the available catalogs and we considered them as [CII] candidates. We used the 8 confirmed [CII] and the 4 [CII] candidates to build one of the first [CII] LFs at $z\sim 5$. We found that 11 out of these 12 sources have a redshift very similar to that of the ALPINE target in the same pointing, suggesting the presence of overdensities around the targets. Therefore, we split the sample in two (a "clustered" and "field" sub-sample) according to their redshift separation and built two separate LFs. Our estimates suggest that there could be an evolution of the [CII] LF between $z \sim 5$ and $z \sim 0$. By converting the [CII] luminosity to star formation rate we evaluated the cosmic star formation rate density (SFRD) at $z\sim 5$. The clustered sample results in a SFRD $\sim 10$ times higher than previous measurements from UV-selected galaxies. On the other hand, from the field sample (likely representing the average galaxy population) we derived a SFRD $\sim 1.6$ higher compared to current estimates from UV surveys but compatible within the errors. Because of the large uncertainties, observations of larger samples are necessary to better constrain the SFRD at $z\sim 5$. This study represents one of the first efforts aimed at characterizing the demography of [CII] emitters at $z\sim 5$ using a mm-selection of galaxies.

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arXiv2020

Scaling relations and baryonic cycling in local star-forming galaxies: I. The sample

Metallicity and gas content are intimately related in the baryonic exchange cycle of galaxies, and galaxy evolution scenarios can be constrained by quantifying this relation. To this end, we have compiled a sample of ~400 galaxies in the Local Universe, dubbed "MAGMA" (Metallicity And Gas for Mass Assembly), which covers an unprecedented range in parameter space, spanning more than 5 orders of magnitude in stellar mass (Mstar), star-formation rate (SFR), and gas mass (Mgas), and a factor of ~60 in metallicity [Z, 12+log(O/H)]. Stellar masses and SFRs have been recalculated for all the galaxies using IRAC, WISE and GALEX photometry, and 12+log(O/H) has been transformed, where necessary, to a common metallicity calibration. To assess the true dimensionality of the data, we have applied multi-dimensional principal component analyses (PCAs) to our sample. In confirmation of previous work, we find that even with the vast parameter space covered by MAGMA, the relations between Mstar, SFR, Z and Mgas (MHI+MH2) require only two dimensions to describe the hypersurface. To accommodate the curvature in the Mstar-Z relation, we have applied a piecewise 3D PCA that successfully predicts observed 12+log(O/H) to an accuracy of ~0.1dex. MAGMA is a representative sample of isolated star-forming galaxies in the Local Universe, and can be used as a benchmark for cosmological simulations and to calibrate evolutionary trends with redshift.

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arXiv2020

The case for the fundamental $M_{\rm BH}$-$σ$ relation

Strong scaling relations between host galaxy properties (such as stellar mass, bulge mass, luminosity, effective radius etc) and their nuclear supermassive black hole's mass point towards a close co-evolution. In this work, we first review previous efforts supporting the fundamental importance of the relation between supermassive black hole mass and stellar velocity dispersion ($M_{\rm BH}$-$σ_{\rm e}$). We then present further original work supporting this claim via analysis of residuals and principal component analysis applied to some among the latest compilations of local galaxy samples with dynamically measured supermassive black hole masses. We conclude with a review of the main physical scenarios in favour of the existence of a $M_{\rm BH}$-$σ_{\rm e}$ relation, with a focus on momentum-driven outflows.

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arXiv2018

The infrared-luminous progenitors of high-z quasars

Here we explore the infrared (IR) properties of the progenitors of high-z quasar host galaxies. Adopting the cosmological, data constrained semi-analytic model GAMETE/QSOdust, we simulate several independent merger histories of a luminous quasar at z ~ 6, following black hole growth and baryonic evolution in all its progenitor galaxies. We find that a fraction of progenitor galaxies (about 0.4 objects per single luminous quasar) at 6.5 < z < 8 has an IR luminosity of L_IR > 10^13 Lsun (hyper-luminous IR galaxies; HyLIRGs). HyLIRGs progenitors reside in the most massive halos, with dark matter (DM) masses of M_DM ~ 10^12.5 - 10^13 Msun. These systems can be easily observed in their ~ 1 mm-continuum emission in a few seconds of integration time with the Atacama Large Millimeter/submillimeter Array (ALMA), and at least 40% of them host nuclear BH activity that is potentially observable in the soft and hard X-ray band. Our findings are in line with recent observations of exceptional massive DM halos hosting HyLIRGs at z ~ 7, suggesting that z ~ 6 luminous quasars are indeed the signposts of these observed rare peaks in the high-z cosmic density field, and that massive IR-luminous galaxies at higher z are their natural ancestors.

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arXiv2018

Extended and broad Lyman alpha emission around a BAL quasar at z~5

In this work we report deep MUSE observations of a Broad Absorption Line (BAL) quasar at z ~ 5, revealing a Lyman alpha nebula with a maximum projected linear size of ~ 60 kpc around the quasar (down to our 2-sigma SB limit per layer of ~ 9e-19 erg/s/cm^2/arcsec^2 for a 1 arcsec^2 aperture). After correcting for the cosmological surface brightness dimming, we find that our nebula, at z ~ 5, has an intrinsically less extended Lyman alpha 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 Lyman alpha 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 (CGM) of our source, the velocity dispersion of the Lyman alpha emission is very high (FWHM > 1000 km/s), suggesting that in our case we may be probing outflowing material associated with the quasar.

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arXiv2017

Where does galactic dust come from?

Here we investigate the origin of the dust mass (Mdust) observed in the Milky Way (MW) and of dust scaling relations found in a sample of local galaxies from the DGS and KINGFISH surveys. To this aim, we model dust production from Asymptotic Giant Branch (AGB) stars and supernovae (SNe) in simulated galaxies forming along the assembly of a Milky Way-like halo in a well resolved cosmic volume of 4cMpc using the GAMESH pipeline. We explore the impact of different sets of metallicity and mass-dependent AGB and SN dust yields on the predicted Mdust. Our results show that models accounting for grain destruction by the SN reverse shock predict a total dust mass in the MW that is a factor of ~4 lower than observed, and can not reproduce the observed galaxy-scale relations between dust and stellar masses, and dust-to-gas ratios and metallicity, with a smaller discrepancy in galaxies with low metallicity (12 + log(O/H) < 7.5) and low stellar masses (Mstar < 10^7 Msun). In agreement with previous studies, we suggest that competing processes in the interstellar medium must be at play to explain the observed trends. Our result reinforces this conclusion by showing that it holds independently of the adopted AGB and SN dust yields.

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arXiv2017

Molecular gas on large circumgalactic scales at z=3.47

We report ALMA observations of the most massive (star forming) galaxy in the redshift range 3<z<4 within the whole GOODS-S field. We detect a large elongated structure of molecular gas around the massive primeval galaxy, traced by the CO(4-3) emission, and extended over 40 kpc. We infer a mass of the large gaseous structure of Mgas~2-6x10^11 Msun. About 60% of this mass is not directly associated with either the central galaxy or its two lower mass satellites. The CO extended structure is also detected in continuum thermal emission. The kinematics of the molecular gas shows the presence of different components, which cannot be ascribed to simple rotation. Furthermore, on even larger scales, we detect nine additional CO systems within a radius of 250 kpc from the massive galaxy and mostly distributed in the same direction as the CO elongated structure found in the central 40 kpc. The stacked images of these CO systems show detections in the thermal continuum and in the X-rays, suggesting that these systems are forming stars at a rate of 30-120 Msun/yr. We suggest that the extended gas structure, combined with its kinematic properties, and the gas rich star forming systems detected on larger scales, are tracing the inner and densest regions of large scale accreting streams, feeding the central massive galaxy. These results corroborate models of galaxy formation, in which accreting streams are clumpy and undergo some star formation (hence enriching the streams with metals) even before accreting onto the central galaxy.

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