arXiv subjects

Marco Chiaberge

Publications and source records attributed to Marco Chiaberge.

At least 37 records · Page 2Linked to original sources

arXiv2023

Constraints on the narrow-line region of the X-ray quasi-periodic eruption source GSN 069

The origins of quasi-periodic eruptions (QPEs) are poorly understood, although most theoretical explanations invoke an accretion disk around a supermassive black hole. The gas and stellar environments in the galactic nuclei of these sources are also poorly constrained. In this paper, we present an analysis of archival Hubble Space Telescope (HST) images to study the narrow-line [O III] emission in the QPE source GSN 069. We find strong evidence for a compact nuclear [O III] emission region of size $\lesssim 35$ pc, overlaid on top of extended [O III] emission up to 2 kpc away from the nucleus. The age of the accretion system is estimated to be between 10 and 100 yr. The [O III] luminosity of the compact region was measured to be $(2.1 \pm 0.3) \times 10^{40}\,\rm erg\,s^{-1}$. Based on CLOUDY simulations, we constrain that the [O III] emitting gas has a hydrogen number density in the range $5 \times 10^{3} < n_{\rm H} \lesssim 10^{8}\,\rm cm^{-3}$ and volume filling factor $f_{\rm V} < 2 \times 10^{-3}$. We suggest that the dense gas in the nuclear region of GSN 069 originates from molecular clouds (with total mass $\gtrsim 3 \times 10^{3}\,M_{\odot}$), which are freshly ionised by the soft X-ray photons from the accretion disk. We predict possible evolution of the compact narrow-line region on emission-line diagnostic diagrams, and hence future HST or integral-field unit observations can be used to further pin down the age of this puzzling system.

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arXiv2022

Compact dust emission in a gravitationally lensed massive quiescent galaxy at z = 2.15 revealed in ~130 pc-resolution observations by ALMA

We present new observations of MRG-M2129, a quiescent galaxy at z = 2.15 with the Atacama Large Millimeter/submillimeter Array (ALMA). With the combination of the gravitational lensing effect by the foreground cluster and the angular resolution provided by ALMA, our data reveal 1.2 mm continuum emission at $\sim130$ pc angular resolution. Compact dust continuum is detected at 7.9 $σ$ in the target but displaced from its stellar peak position by $62 \pm 38$ mas, or $\sim169 \pm 105$ pc in the source plane. We find considerably high dust-to-stellar mass ratio, $4 \times 10^{-4}$. From non-detection of the [C i] 3P2 -> 3P1 line, we then derive $3 σ$ upper limits on the molecular gas-to-dust mass ratio $δ_\mathrm{GDR} < 60$ and the molecular gas-to-stellar mass ratio fH2 < 2.3%. The derived $δ_\mathrm{GDR}$ is $>2\times$ smaller than the typical value assumed for quiescent galaxies in the literature. Our study supports that there exists a broad range of $δ_\mathrm{GDR}$ and urges submillimeter follow-up observations of quenching/recently quenched galaxies at similar redshifts. Based on the derived low $δ_\mathrm{GDR}$ and other observed dust properties, we argue that the central black hole is still active and regulates star formation in the system. Our study exhibits a rare case of a gravitationally lensed type 2 QSO harbored by a quiescent galaxy.

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arXiv2022

NGC 3147: a prototypical low-luminosity active galactic nucleus with double-peaked optical and ultraviolet lines

A previous narrow-slit ($0.1$ arcsec) Hubble Space Telescope observation unveiled a broad relativistic H$α$ profile in NGC3147, a low-luminosity ($\mathrm{L_{bol}}\sim10^{42}$ erg s$^{-1}$), low-Eddington ratio ($\mathrm{L_{bol}/L_{Edd}}\sim10^{-4}$) active galactic nucleus (AGN), formerly believed to be a candidate true type 2 AGN intrinsically lacking the broad-line region. The new observations presented here confirm the double-peaked profile of the H$α$ line, which further shows variability both in flux and in the inner radius of the emitting disc with respect to the previous epoch. Similar disc line profiles are also found in prominent ultraviolet (UV) lines, in particular Ly$α$ and C IV. The new data also allow us to build a simultaneous subarcsec optical-to-X-ray spectral energy distribution of NGC3147, which is characterized by the absence of a thermal UV bump, and an emission peak in the X-rays. The resulting very flat $α_{ox}=-0.82$ is typical of low-luminosity AGN, and is in good agreement with the extrapolation to low luminosities of the well-known trend with luminosity observed in standard AGN. Indeed, we are possibly observing the accretion disc emission in NGC3147 in the optical, close to the expected peak. On the other hand, the steep -2 UV power law may be Comptonization of that cold disc by a warm corona, what is instead generally observed as a `soft excess' in more luminous AGN.

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arXiv2021

Redshift identification of X-ray selected active galactic nuclei in the J1030 field: searching for large-scale structures and high-redshift sources

We publicly release the spectroscopic and photometric redshift catalog of the sources detected with Chandra in the field of the $z$=6.3 quasar SDSS J1030+0525. This is currently the fifth deepest X-ray field, and reaches a 0.5-2 keV flux limit $f_{\rm 0.5-2}$=6$\times$10$^{-17}$ erg s$^{-1}$ cm$^{-2}$. By using two independent methods, we measure a photometric redshift for 243 objects, while 123 (51%) sources also have a spectroscopic redshift, 110 of which coming from an INAF-Large Binocular Telescope (LBT) Strategic Program. We use the spectroscopic redshifts to determine the quality of the photometric ones, and find it in agreement with that of other X-ray surveys which used a similar number of photometric data-points. In particular, we measure a sample normalized median absolute deviation $σ_{NMAD}$=1.48||$z_{phot}$-$z_{spec}$||/(1+$z_{spec}$)=0.065. We use these new spectroscopic and photometric redshifts to study the properties of the Chandra J1030 field. We observe several peaks in our spectroscopic redshift distribution between $z$=0.15 and $z$=1.5, and find that the sources in each peak are often distributed across the whole Chandra field of view. This evidence confirms that X-ray selected AGN can efficiently track large-scale structures over physical scales of several Mpc. Finally, we computed the Chandra J1030 $z>$3 number counts: while the spectroscopic completeness at high-redshift of our sample is limited, our results point towards a potential source excess at $z\geq$4, which we plan to either confirm or reject in the near future with dedicated spectroscopic campaigns.

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arXiv2021

Lower-Luminosity Obscured AGN Host Galaxies are Not Predominantly in Major-Merging Systems at Cosmic Noon

For over 60 years, the scientific community has studied actively growing central super-massive black holes (active galactic nuclei -- AGN) but fundamental questions on their genesis remain unanswered. Numerical simulations and theoretical arguments show that black hole growth occurs during short-lived periods ($\sim$ 10$^{7}$ -10$^{8}$ yr) of powerful accretion. Major mergers are commonly invoked as the most likely dissipative process to trigger the rapid fueling of AGN. If the AGN-merger paradigm is true, we expect galaxy mergers to coincide with black hole accretion during a heavily obscured AGN phase (N$_H$ $ > 10^{23}$ cm$^{-2}$). Starting from one of the largest samples of obscured AGN at 0.5 $<$ $z$ $<$ 3.1, we select 40 non-starbursting lower-luminosity obscured AGN. We then construct a one-to-one matched redshift- and near-IR magnitude-matched non-starbursting inactive galaxy control sample. Combining deep color \textit{Hubble Space Telescope} imaging and a novel method of human classification, we test the merger-AGN paradigm prediction that heavily obscured AGN are strongly associated with galaxies undergoing a major merger. On the total sample of 80 galaxies, we estimate each individual classifier's accuracy at identifying merging galaxies/post-merging systems and isolated galaxies. We calculate the probability of each galaxy being in either a major merger or isolated system, given the accuracy of the human classifiers and the individual classifications of each galaxy. We do not find statistically significant evidence that obscured AGN at cosmic noon are predominately found in systems with evidence of significant merging/post-merging features.

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arXiv2021

Merger or Not: Accounting for Human Biases in Identifying Galactic Merger Signatures

Significant galaxy mergers throughout cosmic time play a fundamental role in theories of galaxy evolution. The widespread usage of human classifiers to visually assess whether galaxies are in merging systems remains a fundamental component of many morphology studies. Studies that employ human classifiers usually construct a control sample, and rely on the assumption that the bias introduced by using humans will be evenly applied to all samples. In this work, we test this assumption and develop methods to correct for it. Using the standard binomial statistical methods employed in many morphology studies, we find that the merger fraction, error, and the significance of the difference between two samples are dependent on the intrinsic merger fraction of any given sample. We propose a method of quantifying merger biases of individual human classifiers and incorporate these biases into a full probabilistic model to determine the merger fraction and the probability of an individual galaxy being in a merger. Using 14 simulated human responses and accuracies, we are able to correctly label a galaxy as ''merger'' or ''isolated'' to within 1\% of the truth. Using 14 real human responses on a set of realistic mock galaxy simulation snapshots our model is able to recover the pre-coalesced merger fraction to within 10\%. Our method can not only increase the accuracy of studies probing the merger state of galaxies at cosmic noon, but also can be used to construct more accurate training sets in machine learning studies that use human classified data-sets.

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arXiv2021

Clustering of red and blue galaxies around high-redshift 3C radio sources as seen by the Hubble Space Telescope

To properly understand the evolution of high-redshift galaxy clusters, both passive and star-forming galaxies have to be considered. Here we study the clustering environment of 21 radio galaxies and quasars at 1 1.6, red overdensities at 1.2<z<1.6, and red overdensities with an increased deficit of central blue galaxies at z<1.2. Only a few 3C sources show a blue overdensity tracing active star-formation in the cluster centers; this rarity could indicate that the powerful quasar activity may quench star-formation in the vicinity of most radio sources. The derived number of central luminous red galaxies and the radial density profiles are comparable to those found in local clusters, indicating that some 3C clusters are already mass-rich and compact.

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arXiv2020

The web of the Giant: spectroscopic confirmation of a Large Scale Structure around the z=6.31 quasar SDSS J1030+0524

We report on the spectroscopic confirmation of a large scale structure around the luminous, z=6.31 QSO SDSS~J1030+0524, that is powered by a billion solar mass black hole. The structure is populated by at least six members, four Lyman Break Galaxies (LBGs) and two Lyman Alpha Emitters (LAEs). The four LBGs have been identified among a sample of 21 i-band dropouts with z{AB}<25.5 selected up to projected separations of 5 physical Mpc (15 arcmin) from the QSO. Their redshifts have been determined through up to 8hr-long multi-object spectroscopic observations at 8-10m class telescopes. The two LAEs have been identified in a 6hr VLT/MUSE observation centered on the QSO. The redshifts of the six galaxies cover the range 6.129-6.355. Assuming that peculiar velocities are negligible, this range corresponds to radial separations of +/-5 physical Mpc from the QSO, that is comparable to the projected scale of the observed LBG distribution on the sky. We conservatively estimate that this structure is significant at >3.5 sigma level, and that the level of the galaxy overdensity is at least 1.5-2 within the large volume sampled (~780 physical Mpc^3). The spectral properties of the six member galaxies (Lyalpha strength and UV luminosity) are similar to those of field galaxies at similar redshifts. This is the first spectroscopic identification of a galaxy overdensity around a super-massive black hole in the first billion years of the Universe. Our finding lends support to the idea that the most distant and massive black holes form and grow within massive (>10^{12} Msun) dark matter halos in large scale structures, and that the absence of earlier detections of such systems was likely due to observational limitations.

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arXiv2020

A Large Population of Obscured AGN in Disguise as Low Luminosity AGN in Chandra Deep Field South

Population synthesis models of actively accreting super-massive black holes (or active galactic nuclei -- AGN) predict a large fraction that must grow behind dense, obscuring screens of gas and dust. Deep X-ray surveys are thought to have provided the most complete and unbiased samples of AGN, but there is strong observational evidence that a portion of the population of obscured AGN is being missed. In this paper we use a sample of AGN derived from the deepest X-ray survey to date, the Chandra 7Ms GOODS-South Survey, to investigate the nature of low flux X-ray sources. We make full use of the extensive multi-wavelength coverage of the GOODS-South field, and cross-match our objects with wavelengths from the Radio to the IR. We find the low X-ray flux AGN in our sample have X-ray luminosities that indicate low-luminosity AGN classification, while their radio, infrared and optical counterparts indicate moderate to powerful AGN classification. We find the predicted column densities is on average an order of magnitude higher than the calculated column densities via X-ray detections for X-ray faint sources. We interpret our results as evidence of obscured AGN disguising as low-luminosity AGN via their X-ray luminosities. When we compare the estimation of the obscured AGN space density with and without these objects, we find a difference of 40% in the lowest X-ray luminosity regime probed by our sample.

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arXiv2020

TXS 2116$-$077: A Gamma-ray Emitting Relativistic Jet Hosted in a Galaxy Merger

What triggers collimated relativistic outflows or jets, from the centers of galaxies remains a fundamental question in astrophysics. The merging of two galaxies has been proposed to realize the conditions to successfully launch and drive such jets into the intergalactic medium. However, evidences for the operation of this mechanism are scarce. Here we report the first unambiguous detection of an ongoing merger of a narrow-line Seyfert 1 galaxy, TXS 2116$-$077, hosting a closely aligned, $γ$-ray emitting relativistic jet with a Seyfert 2 galaxy at a separation of $\sim$12 kpc, using the observations taken with 8.2 m Subaru telescope. Our subsequent followup observations with 10.4 m Gran Telescopio Canarias, 4.2 m William Herschel Telescope, and Chandra X-ray observatory have provided what is likely to be the first glimpse of the merging environment hosting a closely aligned relativistic jet. Our finding that the jet is considerably younger than the merger demonstrates that jet activity can be triggered by galaxy mergers and that $γ$-ray detected narrow-line Seyfert 1 galaxies represent the beginning phase of that activity. These results also highlight the crucial role of mergers in shaping the fate of galaxies in their cosmological evolution and are consistent with recent studies focused on the host galaxy imaging of this enigmatic class of active galactic nuclei.

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arXiv2020

Molecular Gas Heating and Modified Dust Properties in Active Galaxies: Growing Black Holes or Tidal Shocks?

We investigate if and how growing super-massive black holes (SMBH) known as Active Galactic Nuclei (AGN) and gravitational interactions affect the warm molecular gas and dust of galaxies. Our analysis focuses on the morphologies and warm ISM properties of 630 galaxies at z < 0.1. We use grizy images from the Pan-STARRS survey to classify the galaxies into mergers, early mergers, and non-mergers. We use MIR spectroscopic measurements of emission from rotational H2 transitions, dust and PAH features, and silicate emission or absorption lines at 9.7 microns to study how gravitational interactions impact the warm ISM in AGN and non-AGN hosts. We find that in AGN-hosts, the ISM is warmer, the ratios of H2 to PAHs are larger, the PAH emission line ratios and silicate strengths have a wider range of values than in non-AGN hosts. We find some statistical differences between the H2 emission of mergers and non-mergers, but those differences are less statistically significant than those between AGN and non-AGN hosts.

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arXiv2019

Host galaxies of high-redshift extremely red and obscured quasars

We present Hubble Space Telescope 1.4-1.6 micron images of the hosts of ten extremely red quasars (ERQs) and six type 2 quasar candidates at z=2-3. ERQs, whose bolometric luminosities range between 10^47 and 10^48 erg/sec, show spectroscopic signs of powerful ionized winds, whereas type 2 quasar candidates are less luminous and show only mild outflows. After performing careful subtraction of the quasar light, we clearly detect almost all host galaxies. The median rest-frame B-band luminosity of the ERQ hosts in our sample is 10^11.2 L_Sun, or 4 L* at this redshift. Two of the ten hosts of ERQs are in ongoing mergers. The hosts of the type 2 quasar candidates are 0.6 dex less luminous, with 2/6 in likely ongoing mergers. Intriguingly, despite some signs of interaction and presence of low-mass companions, our objects do not show nearly as much major merger activity as do high-redshift radio-loud galaxies and quasars. In the absence of an overt connection to major ongoing gas-rich merger activity, our observations are consistent with a model in which the near-Eddington accretion and strong feedback of ERQs are associated with relatively late stages of mergers resulting in early-type remnants. These results are in some tension with theoretical expectations of galaxy formation models, in which rapid black hole growth occurs within a short time of a major merger. Type 2 quasar candidates are less luminous, so they may instead be powered by internal galactic processes.

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arXiv2019

HST unveils a compact mildly relativistic Broad Line Region in the candidate true type 2 NGC 3147

NGC 3147 has been considered the best case of a true type 2 AGN: an unobscured AGN, based on the unabsorbed compact X-ray continuum, which lacks a broad line region (BLR). However, the very low luminosity of NGC 3147 implies a compact BLR, which produces very broad lines, hard to detect against the dominant background host galaxy. Narrow (0.1"x0.1") slit HST spectroscopy allowed us to exclude most of the host galaxy light, and revealed an H$α$ line with an extremely broad base (FWZI$\sim27\,000$ km s$^{-1}$). The line profile shows a steep cutoff blue wing and an extended red wing, which match the signature of a mildly relativistic thin accretion disk line profile. It is indeed well fit with a nearly face on thin disk, at $i\sim23^\circ$, with an inner radius at $77\pm15$ r$_g$, which matches the prediction of $62^{+18}_{-14}$ r$_g$ from the $R_{\rm BLR} \sim L^{1/2}$ relation. This result questions the very existence of true type 2 AGN. Moreover, the detection of a thin disk, which extends below 100 r$_g$ in an $L/L_{\rm Edd}\sim10^{-4}$ system, contradicts the current view of the accretion flow configuration at extremely low accretion rates.

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arXiv2018

HST emission-line images of nearby 3CR radio galaxies: two photoionization, accretion and feedback modes

We present HST/ACS narrow-band images of a low-z sample of 19 3C radio galaxies to study the H$α$ and [OIII] emissions from the narrow-line region (NLR). Based on nuclear emission line ratios, we divide the sample into High and Low Excitation Galaxies (HEGs and LEGs). We observe different line morphologies, extended line emission on kpc scale, large [OIII]/H$α$ scatter across the galaxies, and a radio-line alignment. In general, HEGs show more prominent emission line properties than LEGs: larger, more disturbed, more luminous, and more massive regions of ionized gas with slightly larger covering factors. We find evidence of correlations between line luminosities and (radio and X-ray) nuclear luminosities. All these results point to a main common origin, the active nucleus, which ionize the surrounding gas. However, the contribution of additional photoionization mechanism (jet shocks and star formation) are needed to account for the different line properties of the two classes. A relationship between the accretion, photoionization and feedback modes emerges from this study. For LEGs (hot-gas accretors), the synchrotron emission from the jet represents the main source of ionizing photons. The lack of cold gas and star formation in their hosts accounts for the moderate ionized-gas masses and sizes. For HEGs (cold-gas accretors), an ionizing continuum from a standard disk and shocks from the powerful jets are the main sources of photoionization, with the contribution from star formation. These components, combined with the large reservoir of cold/dust gas brought from a recent merger, account for the properties of their extended emission-line regions.

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arXiv2018

The recoiling black hole candidate 3C 186: spatially-resolved quasar feedback and further evidence of a blue-shifted broad line region

We present the results of integral field spectroscopy of the gravitational wave (GW) recoiling black hole candidate 3C 186. The goal of the observations is to study the kinematics of the [OIII]5007 narrow emission line region (NLR) of the quasar, and investigate the origin of the velocity offsets originally measured for different UV lines. The results show that i) the spatial structure of the NLR is complex. The [OIII]5007 line shows significant velocity offsets with respect to the systemic redshift of the source. Different components at different velocities (-670, -100, + 75 km s^-1) are produced in different regions of the source. ii) we detect both the narrow and the broad components of the Hbeta line. The narrow component generally follows the kinematics of the [OIII] line, while the broad component is significantly blue-shifted. The peak of the broad line is near the blue end, or possibly outside of the sensitivity band of the instrument, implying a velocity offset of >~1800 km s^-1. This result is in agreement with the interpretation of the QSO as a GW recoiling black hole. The properties of the NLR show that the observed outflows are most likely the effect of radiation pressure on the (photoionized) gas in the interstellar medium of the host galaxy.

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arXiv2018

Detection of an optical/UV jet/counterjet and Multiple Spectral Components in M84

We report an optical/UV jet and counterjet in M84, previously unreported in archival HST imaging. With archival VLA, ALMA, and Chandra imaging, we examine the first well-sampled spectral energy distribution of the inner jet of M84, where we find that multiple co-spatial spectral components are required. In particular, the ALMA data reveal that the radio spectrum of all four knots in the jet turns over at approximately 100 GHz, which requires a second component for the bright optical/UV emission. Further, the optical/UV has a soft spectrum and is inconsistent with the relatively flat X-ray spectrum, which indicates a third component at higher energies. Using archival VLA imaging, we have measured the proper motion of the innermost knots at 0.9+/-0.6 and 1.1+/-0.4 c, which when combined with the low jet-to-counterjet flux ratio yields an orientation angle for the system of 74 (+9,-18) degrees. In the radio, we find high fractional polarization of the inner jet of up to 30% while in the optical no polarization is detected (< 8%). We investigate different scenarios for explaining the particular multi-component SED of the knots. Inverse Compton models are ruled out due to the extreme departure from equipartition and the unrealistically high total jet power required. The multi-component SED can be naturally explained within a leptohadronic scenario, but at the cost of very high power in relativistic protons. A two-component synchrotron model remains a viable explanation, but more theoretical work is needed to explain the origin and properties of the electron populations.

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arXiv2017

Proper Motions of Jets on the Kiloparsec Scale: New Results with HST

The Hubble Space Telescope recently celebrated 25 years of operation. Some of the first images of extragalactic optical jets were taken by HST in the mid-1990s; with time baselines on the order of 20 years and state-of-the-art astrometry techniques, we are now able to reach accuracies in proper-motion measurements on the order of a tenth of a milliarcsecond per year. We present the results of a recent HST program to measure the kiloparsec-scale proper motions of eleven nearby optical jets with Hubble, the first sample of its kind. When paired with VLBI proper-motion measurements on the parsec scale, we are now able to map the full velocity profile of these jets from near the black hole to the final deceleration as they extend out into and beyond the host galaxy. We see convincing evidence that weak-flavor jets (i.e., FR Is) have a slowly increasing jet speed up to 100 pc from the core, where superluminal components are first seen.

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arXiv2016

The Environment of z >1 3CR Radio Galaxies and QSOs: From Proto-Clusters to Clusters of Galaxies?

We study the cluster environment for a sample of 21 radio loud AGN from the 3CR catalog at z>1, 12 radio galaxies and 9 quasars with HST images in the optical and IR. We use two different approaches to determine cluster candidates. We identify the early type galaxies (ETGs) in every field by modeling each of the sources within a 40" radius of the targets with a Sersic profile. Using a simple passive evolution model, we derive the expected location of the ETGs on the red sequence (RS) in the color-magnitude diagram for each of the fields of our sources. For seven targets, the model coincides with the position of the ETGs. A second approach involves a search for over densities. We compare the object densities of the sample as a whole and individually against control fields taken from the GOODS-S region of 3D-HST survey. With this method we determine the fields of 10 targets to be cluster candidates. Four cluster candidates are found by both methods. The two methods disagree in some cases, depending on the specific properties of each field. For the most distant radio galaxy in the 3CR catalog (3C257 at z = 2.47), we identify a population of bluer ETGs that lie on the expected location of the RS model for that redshift. This appears to be the general behavior of ETGs in our fields and it is possibly a signature of the evolution of such galaxies. Our results are consistent with half of the z > 1 radio galaxies being located in dense, rapidly evolving environments.

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