| 1. |
- Belete, A. Bewketu, et al.
(författare)
-
Molecular gas kinematics in the nuclear region of nearby Seyfert galaxies with ALMA
- 2021
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 654
-
Tidskriftsartikel (refereegranskat)abstract
- Context. The study of the distribution, morphology, and kinematics of cold molecular gas in the nuclear and circumnuclear regions of active galactic nuclei (AGNs) helps to characterise and hence to quantify the impact of the AGNs on the host galaxy over its lifetime. Aims. We present the analysis of the molecular gas in the nuclear regions of three Seyfert galaxies, NGC 4968, NGC 4845, and MCG-06-30-15, using Atacama Large sub-Millimetre Array (ALMA) observations of the CO(2-1) emission line. The aim is to determine the kinematics of the gas in the central (∼1 kpc) region and thereby to probe nuclear fueling and feedback of AGNs. Methods. We used two different softwares, namely the 3D-Based Analysis of Rotating Object via Line Observations and DiskFit, to model the kinematics of the gas in the molecular disc, and thereby to determine the gas rotation and any kinematical perturbations. Results. Circular motions dominate the kinematics of the molecular gas in the central discs, mainly in NGC 4845 and MCG-06-30-15; however there is clear evidence of non-circular motions in the central (∼1 kpc) region of NGC 4845 and NGC 4968. The strongest non-circular motion is detected in the inner disc of NGC 4968, mainly along the minor kinematic axis, with a velocity ∼115 km s-1. Of all DiskFit models, the bisymmetric model is found to give the best fit for NGC 4968 and NGC 4845, indicating that the observed non-circular motions in the inner disc of these galaxies could result from the nuclear barred structure, where the gas streams in elliptical orbits aligned along the bar. If the dynamics of NGC 4968 is modelled as a corotation pattern just outside of the bar, the bar pattern speed becomes ωb = 52 km s-1 kpc-1; the corotation is set at 3.5 kpc; and the inner Lindblad resonance (ILR) ring is R = 300 pc, corresponding to the CO emission ring. In the NGC 4968 galaxy, the torques exerted on the gas by the bar are positive in the centre, within the gas nuclear ring, and negative outside. This shows that the gas is transiently trapped in the ILR. The comparison of the CO intensity maps with the map of the cold dust emission shows an absence of CO in the centre of NGC 4968; also the dust distribution and CO emission in and around the centre of NGC 4845 have similar extensions. The 1.2 mm ALMA continuum is peaked and compact in NGC 4968 and MCG-06-30-15, but their CO(2-1) emissions have extended distributions. Allowing the CO-to-H2 conversion factor αCO between 0.8 and 3.2, which is typical of nearby galaxies of the same type, the molecular mass M(H2) is estimated to be ∼3 - 12 × 107 M⊙ (NGC 4968), ∼9 - 36 × 107 M⊙ (NGC 4845), and ∼1 - 4 × 107 M⊙ (MCG-06-30-15). Conclusions. We conclude that the observed non-circular motions in the molecular disc of NGC 4968 and likely those seen in NGC 4845 are due to the presence of the bar in the nuclear region. We discuss the possibility that the observed pattern in the kinematics might be a consequence of the presence of AGNs, and this might be the case for NGC 4845. At the current spectral and spatial resolution and sensitivity, we cannot claim any strong evidence in these sources of the long sought feedback or feeding effect resulting from the presence of AGNs.
|
|
| 2. |
- Bonanomi, Francesca, et al.
(författare)
-
Another X-ray UFO without a momentum-boosted molecular outflow : ALMA CO(1–0) observations of the galaxy pair IRAS 05054+1718
- 2023
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 673
-
Tidskriftsartikel (refereegranskat)abstract
- We present Atacama Large Millimetre/submillimetre Array (ALMA) CO(1–0) observations of the nearby infrared luminous (LIRG) galaxy pair IRAS 05054+1718 (also known as CGCG 468-002), as well as a new analysis of X-ray data of this source collected between 2012 and 2021 using the Nuclear Spectroscopic Telescope Array (NuSTAR), Swift, and the XMM-Newton satellites. The western component of the pair, NED01, hosts a Seyfert 1.9 nucleus that is responsible for launching a powerful X-ray ultra-fast outflow (UFO). Our X-ray spectral analysis suggests that the UFO could be variable or multi-component in velocity, ranging from v/c ∼ −0.12 (as seen in Swift) to v/c ∼ −0.23 (as seen in NuSTAR), and constrains its momentum flux to be ṗoutX−ray ∼ (4 ± 2) × 1034 g cm s−2. The ALMA CO(1–0) observations, obtained with an angular resolution of 2.2″, although targeting mainly NED01, also include the eastern component of the pair, NED02, a less-studied LIRG with no clear evidence of an active galactic nucleus (AGN). We study the CO(1–0) kinematics in the two galaxies using the 3D-BAROLO code. In both sources we can model the bulk of the CO(1–0) emission with rotating disks and, after subtracting the best-fit models, we detect compact residual emission at S/N = 15 within ∼3 kpc of the centre. A molecular outflow in NED01, if present, cannot be brighter than such residuals, implying an upper limit on its outflow rate of Ṁoutmol ≲ 19 ± 14 M⊙ yr−1 and on its momentum rate of ṗoutmol ≲ (2.7 ± 2.4) × 1034 g cm s−1. Combined with the revised energetics of the X-ray wind, we derive an upper limit on the momentum rate ratio of ṗoutmol/ṗoutX−ray < 0.67. We discuss these results in the context of the expectations of AGN feedback models, and we propose that the X-ray disk wind in NED01 has not significantly impacted the molecular gas reservoir (yet), and we can constrain its effect to be much smaller than expectations of AGN ‘energy-driven’ feedback models. We also consider and discuss the hypothesis of asymmetries of the molecular disk not properly captured by the 3D-BAROLO code. Our results highlight the challenges in testing the predictions of popular AGN disk-wind feedback theories, even in the presence of good-quality multi-wavelength observations.
|
|
| 3. |
- Braito, V, et al.
(författare)
-
Dramatic Changes in the Observed Velocity of the Accretion Disk Wind in MCG-03-58-007 Are Revealed by XMM-Newton and NuSTAR
- 2022
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 926:2
-
Tidskriftsartikel (refereegranskat)abstract
- Past X-ray observations of the nearby Seyfert 2 MCG-03-58-007 revealed the presence of a powerful and highly variable disk wind, where two possible phases outflowing with vout1/c ∼ −0.07 and vout2/c ∼ −0.2 were observed. Multi-epoch X-ray observations, covering the period from 2010 to 2018, showed that the lower-velocity component is persistent, as it was detected in all the observations, while the faster phase outflowing with vout2/c ∼ −0.2 appeared to be more sporadic. Here we present the analysis of a new monitoring campaign of MCG-03-58-007 performed in 2019 May–June and consisting of four simultaneous XMM-Newton and NuSTAR observations. We confirm that the disk wind in MCG-03-58-007 is persistent, as it is detected in all the observations, and powerful, having a kinetic power that ranges between 0.5% and 10% of the Eddington luminosity. The highly ionized wind (log(ξ/erg cm s−1) ∼ 5) is variable in both the opacity and, remarkably in its velocity. This is the first time where we have observed a substantial variability of the outflowing velocity in a disk wind, which dropped from vout/c ∼ −0.2 (as measured in the first three observations) to vout/c ∼ −0.074 in just 16 days. We conclude that such a dramatic and fast variability of the outflowing velocity could be due to the acceleration of the wind, as recently proposed by Mizumoto et al. Here, the faster wind, seen in the first three observations, is already accelerated to vout/c ∼ −0.2, while in the last observation our line of sight intercepts only the slower, pre-accelerated streamline.
|
|
| 4. |
- Braito, V., et al.
(författare)
-
The stratified disc wind of MCG-03-58-007
- 2021
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 500:1, s. 291-300
-
Tidskriftsartikel (refereegranskat)abstract
- Past Suzaku, XMM-Newton, and NuSTAR observations of the nearby (z = 0.03233) bright Seyfert 2 galaxy MCG-03-58-007 revealed the presence of two deep and blue-shifted iron K-shell absorption line profiles. These could be explained with the presence of two phases of a highly ionized, high column density accretion disc wind outflowing with v(out1) similar to-0.1c and v(out2) similar to -0.2c. Here we present two new observations of MCG-03-58-007: one was carried out in 2016 with Chandra and one in 2018 with Swift. Both caught MCG-03-58-007 in a brighter state (F2-10 (keV) similar to 4 x 10(-12) erg cm(-2) s(-1)) confirming the presence of the fast disc wind. The multi-epoch observations of MCG-03-58-007 covering the period from 2010 to 2018 were then analysed. These data show that the lower velocity component outflowing with v(out1) similar to -0.072 +/- 0.002c is persistent and detected in all the observations, although it is variable in column density in the range N-H similar to 3-8 x 102(3) cm(-2). In the 2016 Swift observation we detected again the second faster component outflowing with v(out2) similar to-0.2c, with a column density (N-H = 7.0(-4.1)(+5.6) x 10(23) cm(-2)), similar to that seen during the Suzaku observation. However during the Chandra observation 2 yr earlier, this zone was not present (N-H < 1.5 x 10(23) cm(-2)), suggesting that this faster zone is intermittent. Overall the multi-epochs observations show that the disc wind in MCG-03-58-007 is not only powerful, but also extremely variable, hence placing MCG-03-58-007 among unique disc winds such as the one seen in the famous QSO PDS456. One of the main results of this investigation is the consideration that these winds could be extremely variable, sometime appearing and sometime disappearing; thus to reach solid and firm conclusions about their energetics multiple observations are mandatory.
|
|
| 5. |
|
|
| 6. |
- Della Bruna, Lorenza, et al.
(författare)
-
Stellar feedback in M83 as observed with MUSE I. Overview, an unprecedented view of the stellar and gas kinematics and evidence of outflowing gas
- 2022
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 660
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Young massive stars inject energy and momentum into the surrounding gas, creating a multi-phase interstellar medium (ISM) and regulating further star formation. The main challenge of studying stellar feedback proves to be the variety of scales spanned by this phenomenon, ranging from the immediate surrounding of the stars (H II regions, 10s pc scales) to galactic-wide kiloparsec scales.Aims. We present a large mosaic (3.8 × 3.8 kpc) of the nearby spiral galaxy M83, obtained with the MUSE instrument at ESO Very Large Telescope. The integral field spectroscopy data cover a large portion of the optical disk at a resolution of ∼20 pc, allowing the characterisation of single H II regions while sampling diverse dynamical regions in the galaxy.Methods. We obtained the kinematics of the stars and ionised gas, and compared them with molecular gas kinematics observed in CO(2-1) with the ALMA telescope array. We separated the ionised gas into H II regions and diffuse ionised gas (DIG) and investigated how the fraction of Hα luminosity originating from the DIG (fDIG) varies with galactic radius.Results. We observe that both stars and gas trace the galactic disk rotation, as well as a fast-rotating nuclear component (30″ ≃ 700 pc in diameter), likely connected to secular processes driven by the galactic bar. In the gas kinematics, we observe a stream east of the nucleus (50″ ≃ 1250 pc in size), redshifted with respect to the disk. The stream is surrounded by an extended ionised gas region (1000 × 1600 pc) with enhanced velocity dispersion and a high ionisation state, which is largely consistent with being ionised by slow shocks. We interpret this feature as either the superposition of the disk and an extraplanar layer of DIG, or as a bar-driven inflow of shocked gas. A double Gaussian component fit to the Hα line also reveals the presence of a nuclear biconic structure whose axis of symmetry is perpendicular to the bar. The two cones (20″ ≃ 500 pc in size) appear blue- and redshifted along the line of sight. The cones stand out for having an Hα emission separated by up to 200 km s−1 from that of the disk, and a high velocity dispersion ∼80–200 km s−1. At the far end of the cones, we observe that the gas is consistent with being ionised by shocks. These features had never been observed before in M83; we postulate that they are tracing a starburst-driven outflow shocking into the surrounding ISM. Finally, we obtain fDIG ∼ 13% in our field of view, and observe that the DIG contribution varies radially between 0.8 and 46%, peaking in the interarm region. We inspect the emission of the H II regions and DIG in ‘BPT’ diagrams, finding that in H II regions photoionisation accounts for 99.8% of the Hα flux, whereas the DIG has a mixed contribution from photoionisation (94.9%) and shocks (5.1%).
|
|
| 7. |
- Jung, Dooseok Escher, et al.
(författare)
-
Universal Upper End of the Stellar Initial Mass Function in the Young and Compact LEGUS Clusters
- 2023
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 954:2
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the variation in the upper end of the stellar initial mass function (uIMF) in 375 young and compact star clusters in five nearby galaxies within ∼5 Mpc. All the young stellar clusters (YSCs) in the sample have ages ≲ 4 Myr and masses above 500 M⊙, according to standard stellar models. The YSC catalogs were produced from Hubble Space Telescope images obtained as part of the Legacy ExtraGalactic UV Survey (LEGUS) Hubble treasury program. They are used here to test whether the uIMF is universal or changes as a function of the cluster's stellar mass. We perform this test by measuring the Hα luminosity of the star clusters as a proxy for their ionizing photon rate, and charting its trend as a function of cluster mass. Large cluster numbers allow us to mitigate the stochastic sampling of the uIMF. The advantage of our approach relative to previous similar attempts is the use of cluster catalogs that have been selected independently of the presence of Hα emission, thus removing a potential sample bias. We find that the uIMF, as traced by the Hα emission, shows no dependence on cluster mass, suggesting that the maximum stellar mass that can be produced in star clusters is universal, in agreement with previous findings.
|
|
| 8. |
- Pérez, Gustavo, et al.
(författare)
-
StarcNet : Machine Learning for Star Cluster Identification
- 2021
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 907:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present a machine learning (ML) pipeline to identify star clusters in the multicolor images of nearby galaxies, from observations obtained with the Hubble Space Telescope as part of the Treasury Project LEGUS (Legacy ExtraGalactic Ultraviolet Survey). StarcNet (STAR Cluster classification NETwork) is a multiscale convolutional neural network (CNN) that achieves an accuracy of 68.6% (four classes)/86.0% (two classes: cluster/noncluster) for star cluster classification in the images of the LEGUS galaxies, nearly matching human expert performance. We test the performance of StarcNet by applying a pre-trained CNN model to galaxies not included in the training set, finding accuracies similar to the reference one. We test the effect of StarcNet predictions on the inferred cluster properties by comparing multicolor luminosity functions and mass-age plots from catalogs produced by StarcNet and by human labeling; distributions in luminosity, color, and physical characteristics of star clusters are similar for the human and ML classified samples. There are two advantages to the ML approach: (1) reproducibility of the classifications: the ML algorithm's biases are fixed and can be measured for subsequent analysis; and (2) speed of classification: the algorithm requires minutes for tasks that humans require weeks to months to perform. By achieving comparable accuracy to human classifiers, StarcNet will enable extending classifications to a larger number of candidate samples than currently available, thus increasing significantly the statistics for cluster studies.
|
|
| 9. |
- Sirressi, Mattia, et al.
(författare)
-
CLusters in the UV as EngineS (CLUES). I. Survey Presentation and FUV Spectral Analysis of the Stellar Light
- 2022
-
Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 164:5
-
Tidskriftsartikel (refereegranskat)abstract
- The CLusters in the Uv as EngineS (CLUES) survey is a Cosmic Origins Spectrograph (COS) campaign aimed at acquiring the 1130–1770 Å rest-frame spectroscopy of very young (<20 Myr) and massive (>104 M⊙) star clusters in galaxies that are part of the Hubble treasury program Legacy ExtraGalactic UV Survey. In this first paper of a series, we describe the CLUES sample consisting of 20 young star clusters and report their physical properties as derived by both multiwavelength photometry and far-UV (FUV) spectroscopy with Hubble Space Telescope. Thanks to the synergy of the two different data sets, we build a coherent picture of the diverse stellar populations found in each region (with sizes of 40–160 pc). We associate the FUV-brightest stellar population to the central targeted star cluster and the other modeled population to the diffuse stars that are included in the COS aperture. We observe better agreement between photometric and spectroscopic ages for star clusters younger than 5 Myr. For clusters older than 5 Myr, photometry and spectroscopy measurements deviate, with the latter producing older ages, due to the degeneracy of photometric models. FUV spectroscopy enables us to better constrain the stellar metallicities, a parameter that optical colors are insensitive to. Finally, the derived E(B − V) are quite similar, with a tendency for FUV spectroscopy to favor solutions with higher extinctions. The recovered masses are in agreement within a factor of 2 for all of the clusters.
|
|
| 10. |
- Sirressi, Mattia, 1995-, et al.
(författare)
-
CLusters in the Uv as EngineS (CLUES). II. Subkiloparsec-scale Outflows Driven by Stellar Feedback
- 2024
-
Ingår i: Astronomical Journal. - 0004-6256 .- 1538-3881. ; 167:4
-
Tidskriftsartikel (refereegranskat)abstract
- We analyze the far-ultraviolet (1130−1770 Å rest frame) spectroscopy of 20 young (<50 Myr) and massive (>104M⊙) star clusters (YSCs) in 11 nearby star-forming galaxies. We probe the interstellar gas intervening along the line of sight, detecting several metal absorption lines of a wide range of ionization potentials, from 6.0 to 77.5 eV. Multiple-component Voigt fits to the absorption lines are used to study the kinematics of the gas. We find that nearly all targets in the sample feature gas outflowing from 30 up to 190 km s−1, often in both the neutral and ionized phases. The outflow velocities correlate with the underlying stellar population properties directly linked to the feedback: the mass of the YSCs, the photon production rate, and the instantaneous mechanical luminosity produced by stellar winds and supernovae. We detect a neutral inflow in four targets, which we interpret as likely not associated with the star cluster but tracing larger-scale gas kinematics. A comparison between the outflows' energy and that produced by the associated young stellar populations suggests an average coupling efficiency of 10% with a broad scatter. Our results extend the relation found in previous works between galactic outflows and the host galaxy star formation rate to smaller scales, pointing toward the key role that clustered star formation and feedback play in regulating galaxy growth.
|
|
