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Key questions, which arise when one tries to clear up a problem of formation and evolution of galaxies, is the question of energy: what is the energetic budget of AGN owing to form galaxies and provide its subsequent development? Hence, for understanding the formation and evolution of galaxies, it is important to estimate the energetic budget of AGN which we try to do involving radio loud phase of nuclear activity.
We present the discovery of out-flow like plasma emissions with the Suzaku and ASCA data. Those plasmas have a size of ∼150 pc. Remarkably, the southern plasma is in a recombination dominant phase, which is not predicted by standard shock heating. A plausible scenario is either photoionization due to strong jet-like X-rays from Sgr A* or rapid cooling due to adiabatic expansion of a blowout plasma from the Galactic center about 105 years ago.
This work presents the main results from a selection of optical spectra of Seyfert and LINER galaxies taken from the 9th release of the SDSS with detectable coronal emission. A catalogue of 345 Seyfert 1 (Sy1) and Seyfert 2 (Sy2) galaxies with Forbidden High Ionization Lines (FHILs) emission is presented. By analysing their spectra as well as utilising data from the literature we found evidence of anisotropy in optical FHIL emissions between Sy1 and Sy2 galaxies for the following lines: [Ne v] λ3426, [Fe vii] λ6087, [Fe x] λ6374 and [Fe xi] λ7892. Results continue indicating that optical FHILs are not observed in LINER type galaxies.
An object called G2 was recently discovered moving towards the supermassive black hole in the Galactic center. G2 emits infrared (IR) lines and continuum, which allows constraining its properties. The question is still unresolved whether G2 has a central windy star or it is a coreless cloud. Assuming the object is a cloud originating near the apocenter I perform line/continuum IR diagnostics, revisit estimates of non-thermal emission from pericenter passage, and speculate about future observational prospects. This work is partially reported in Shcherbakov (2013) and partially consists of new ideas discussed at the conference.
Active galaxies are most luminous objects in the universe whose spectra are characterized by both permitted and forbidden emission line features. The spectra of Seyfert 1 galaxies and quasars contain strong and broad emission lines of wide ranging ionization potentials. The velocity widths of the lines range from a minimum of ≈ 500 km/s for narrow lines to a maximum of 20,000 km/sec for broad lines. The UV spectra of the active galaxies contain strong and broad emission lines such as Lyα, NV, SiIV, OIV], CIV, CIII] and MgII lines. The widths of the broad lines are attributed to the differential doppler shifts of the emission lines due to the bulk motions of individual clumpy gas clouds in the BLR region. We have anlysed UV spectra of Seyfert 1 galaxies and quasars from IUE satellite archival database to understand the nature of dependence of the emission line properties with the underlying UV continuum. We have undertaken line luminosity correlation studies for Lyα and CIV lines with their underlying UV continuum luminosity at 1125Å, 1425Å & 1625Å. The IUE archival spectra have been reduced for galactic reddening using the E(B-V) and NHI values published continuum luminosity has been observed at 1125Å, 1425Å & 1625Å. The Lyα line line has exhibited strongest linear correlation wavelengths while CIV line has shown at 1425Å and 2625Å wavelengths. These results are empirically consistent with the predictions of the general multi-component photo-ionization models suggesting that the central strong UV continuum has been reprocessed by the clumpy gas clouds of the broad emission region (BLR). A detailed account of the data reduction, UV flux measurement and the significance of line-luminosity correlations are discussed in this paper.
In these proceedings I briefly: (1) review the impact (or “feedback”) that active galactic nuclei (AGN) are predicted to have on their host galaxies and larger scale environment, (2) review the observational evidence for or against these predictions and (3) present new results on ionised outflows in AGN. The observational support for the “maintenance mode” of feedback is strong (caveat the details); AGN at the centre of massive halos appear to be regulating the cooling of hot gas, which could in turn control the levels of future star formation (SF) and black hole growth. In contrast, direct observational support for more rapid forms of feedback, which dramatically impact on SF (i.e., the “quasar mode”), remains elusive. From a systematic study of the spectra of ≈24 000 AGN we find that extreme ionised gas kinematics are common, and are most prevalent in radio bright AGN (L1.4 GHz > 103 W Hz−1). Follow-up IFU observations have shown that these extreme gas kinematics are extended over kilo-parsec scales. However, the co-existence of high-levels of SF, luminous AGN activity and radio jets raises interesting questions on the primary drivers and impact of these outflows. Galaxy-wide, high-mass outflows are being observed in an increasing number of AGN and are a plausible mechanism for the depletion of gas; however, there is still much work to be done to determine the physical processes that drive these outflows and to measure the level of impact that they have on their host galaxies.
Very Long Baseline Interferometry (VLBI) provides the highest angular resolution achievable in astronomy, reaching sub-milliarcsecond scales. For radio loud AGNs, this offers the unique opportunity to directly image and monitor the fine details of the jet structure, approaching the event horizon in the nearest and most supermassive black holes, like in M87. After a quick review of various VLBI facilities, we present results from recent VLBI monitoring projects on two remarkable radio and high energy sources: the radio galaxy M87 and the BL Lac object Mrk421. For the latter, we present a detailed analysis of the jet structure in total intensity and polarization through the whole 2011, during which a multi-wavelength campaign took place. We reveal flux density variability but no significant changes in the jet structure. In M87, we detect and follow the evolution of the core and of the jet feature HST-1; we reveal superluminal motion of components within HST-1, with a possible connection between ejection of new such components and the occurrence of very high energy flares. Estimates on the physical parameters for both sources are given (Doppler factor, viewing angle, magnetic field, etc.).
The Byurakan-IRAS Galaxy (BIG) sample is the result of optical identifications of IRAS PSC sources at high-galactic latitudes using the First Byurakan Survey (FBS) low-dispersion spectra. Among the 1178 objects most are spiral galaxies and many have been proved to be AGN and starburst by spectroscopic observations, as well as there is a number of ULIRGs among these objects. BIG objects contain galaxy pairs, multiples, and small groups that are subject for study on the matter of the real IR-emitter in these systems. Given that these objects are powerful IR sources, they are considered as young systems indicating high rate of evolution and starburst activity exceeding 100 Mo/yr. Spectroscopic observations show that all these systems are physical ones and we were able to measure the mutual distances and sizes for all components. Cross-correlations with the recent more accurate IR catalogues, such as 2MASS and WISE, as well as radio ones (NVSS, FIRST), provided accurate coordinates of the IR source and possibility to find the individual galaxy responsible for the IR. However, in almost half of the cases, IR position indicates the intermediate region between the components, which means that it comes from the system as a whole. Some more MW data have been matched to IR and radio to have an overall understanding on these systems. Given that these systems are mostly interacting/merging ones often containing AGN and most of them may be considered as powerful starbursts, it is possible to study starburst/activity/interaction phenomena and their interrelationship.
The Galactic center supermassive black hole is surrounded by orbiting clouds of gas. These clumps of gas may collide with each other, losing angular momentum and plunging towards the center. Observations of X-ray reflection from molecular clouds surrounding the Galactic center show evidence for enhanced activity of Sagittarius A* during the past few hundred years. These observations enable us to place constraints on the nature of past accretion events responsible for this enhanced activity. We model the source intrinsic luminosity of Sgr A* using multiple accretion events occurring at various moments in time, characterized by a range of angular momentum We also applied our scheme to the case of G2 cloud in the Galactic center.
The Baldwin, Phillips, and Terlevich emission-line ratio diagnostic ([OIII]/Hβ versus [NII]/Hα, hereafter BPT diagram) efficiently separates galaxies whose signal is dominated by star formation (BPT-SF) from those dominated by AGN activity (BPT-AGN). Yet the BPT diagram is limited to z<0.5, the redshift at which [NII]λ6584 leaves the optical spectral window. Using the Sloan Digital Sky Survey (SDSS), we construct a new diagnostic, or TBT diagram, that is based on rest-frame g−z color, [NeIII]λ3869, and [OII]λλ3726+3729 and can be used for galaxies out to z<1.4. The TBT diagram identifies 98.7% of the SDSS BPT-AGN as TBT-AGN and 97% of the SDSS BPT-SF as TBT-SF. Furthermore, it identifies 97% of the OPTX Chandra X-ray selected AGNs as TBT-AGN. This is in contrast to the BPT diagram, which misidentifies 20% of X-ray selected AGNs as BPT-SF.
The current galaxy formation paradigm postulates that a significant amount of gas accretes onto galaxies from the IGM in a cold T ~ 104K phase, and many have argued that this gas should be detectable in diffuse Lyα emission. However, so far, there are no convincing direct detections.
We are conducting a deep (down to 1σ ~ 5 − 10 × 10−19 erg s−1 cm−2 arcsec−2) and the first statistical survey matching the Lyα line around radio-quiet quasars at z ~ 2. By taking advantage of the boost in fluorescent Lyα emission due to the ionizing radiation emitted by a luminous QSO that, like a flashlight, can illuminate the hydrogen in its vicinity, we will be able to constrain some of the properties of the gas sorrounding z ~ 2 QSOs. In particular, with this unique dataset, we can conduct the first deep statistical census of the size, morphology, luminosity, frequency, and covering factor of Lyα emission around QSOs.
We summarize here our recent findings from near-infrared spectroscopy and 1 mm line and continuum observations of a recently identified extended green object (EGO) in Sgr C, whose observational characteristics suggest early-stage massive star formation is taking place. Located on the outskirts of the massive evolved Hii region associated with Sgr C in the Western central molecular zone (CMZ), the EGO measures ∼10″ (0.4 pc at 8.5 kpc). We confirm that early-stage star formation is taking place on the periphery of the Sgr C Hii region. The data show clear detections of two protostellar cores and several knots of H2 and Brackett γ emission alongside a previously detected compact radio source. We calculate the cores' joint mass to be ∼103 M⊙, with column densities of 1-2 × 1024 cm−2. The host molecular clouds mass is approximately 105 M⊙. Despite these favorable conditions, the cloud is curiously devoid of any further star formation, making it comparable to other remarkably quiescent clouds, such as G0.253 in the Eastern CMZ.
To test recent suggestions that the infrared emission of low-luminosity AGN arises in a truncated thin accretion disk, we compare recent, high-resolution IR data with published SED model fits that include emission from the truncated disk. We also fit the data with clumpy torus and optically thin dust shell models. These comparisons suggest that dust can better account for the IR emission of the objects in question than can the truncated disk. That optically thin models give a good fit to the data may support a scenario in which the torus of the AGN unified model does not persist in low accretion rate AGN.
We show that the observed time lag between starburst and AGN activity can be explained by a viscous time lag the gas needs to flow through the AGN's accretion disk before reaching the central black hole. Our calculations reproduce the observed time lag and are in agreement with the observed correlation between black hole mass and stellar velocity dispersion.
Kaz 163 is a close double galaxy. Its southern component S is compact, with a very blue nucleus, in which heated active processes take place. From time to time gas formations are ejected from it, which behave themselves like emission components around the main emission lines Hα and Hβ, around both from their long-wave and short-wave sides. This paper presents the spectral data of new observations, which were carried out with the 2.6m telescope at the Byurakan Astrophysical Observatory in September 2011. During the former observation in October 1981, lines [NII] λλ 6584,6548 were not visible in the spectrum of the component S. In 2001 they were already visible on the spectrum, and on the spectrum obtained in 2011 they already surpassed the intensity of Hα. The magnitude of the component S is also changing: its nucleus is very blue and its U-B = −0m.63. In the soft X-ray spectral range (0.1–2 keV) the flux of the radiation changed by 45% during 55,000 sec, and in the hard one (2–10keV) it changed up to 3.4 times. Photoindices Γ for the soft and hard ranges in the spectrum of galaxy S, unlike other objects, do not so much differ from each other. The mean value for the first interval is approximately 2.5 and is equal −2.0 for the second one. On the histogram of redshifts Kaz 163 corresponds to the first big peak of the distribution. It is concluded that the component S of the galaxy Kaz 163 is a NLS1 galaxy, with the development of their evolution, is in the preliminary stage. Component N is a normal elliptical galaxy with no activity.
The Fermi γ-ray telescope discovered a pair of bubbles at the Galactic center. These structures are spatially-correlated with the microwave emission detected by the WMAP and Planck satellites. These bubbles were likely inflated by a jet launched from the vicinity of a supermassive black hole in the Galactic center. Using MHD simulations, which self-consistently include interactions between cosmic rays and magnetic fields, we build models of the supersonic jet propagation, cosmic ray transport, and the magnetic field amplification within the Fermi bubbles. Our key findings are that: (1) the synthetic Fermi γ-ray and WMAP microwave spectra based on our simulations are consistent with the observations, suggesting that a single population of cosmic ray leptons may simultaneously explain the emission across a range of photon energies; (2) the model fits the observed centrally-peaked microwave emission if a second, more recent, pair of jets embedded in the Fermi bubbles is included in the model. This is consistent with the observationally-based suggestion made by Su & Finkbeiner (2012); (3) the radio emission from the bubbles is expected to be strongly polarized due to the relatively high level of field ordering caused by elongated turbulent vortices. This effect is caused by the interaction of the shocks driven by the jets with the preexisting interstellar medium turbulence; (4) a layer of enhanced rotation measure in the shock-compressed region could exist in the bubble vicinity but the level of this enhancement depends on the details of the magnetic topology.
Photoionization models for AGN, including Seyfert and LINERs are discussed. These photoionization models can be used to derive emission-line diagnostics for AGN that can determine the properties of the AGN and surrounding ISM, including the relative AGN contribution to the EUV radiation field, the hardness of the AGN radiation field, the ionization state of the gas, and the metallicity of the narrow-line region. It is shown how the AGN emission-line diagnostics are expected to change with redshift. Finally, latest application of these models by the author to wide integral field spectroscopy to separate starburst and AGN contributions in composite galaxies are presented.
The star formation rate in the central 500 pc of the Milky Way is lower by a factor of > 10 than expected for the substantial amount of dense gas it contains, which challenges current star formation theories. I discuss which physical mechanisms could be causing this observation and put forward a self-consistent cycle of star formation in the Galactic center, in which the plausible star formation inhibitors are combined. Their ubiquity suggests that the perception of a lowered central SFR should be a common phenomenon in other galaxies with direct implications for galactic star formation and also potentially supermassive black hole growth. I then describe a scenario to explain the presence of super star clusters in the Galactic center environment, in which their formation is triggered by gas streams passing close to the minimum of the global Galactic gravitational potential at the location of the central supermassive black hole, Sgr A*. If this triggering mechanism can be verified, we can use the known time interval since closest approach to Sgr A* to study the physics of stellar mass assembly in an extreme environment as a function of absolute time. I outline the first results from detailed numerical simulations testing this scenario. Finally, I describe a study showing that in terms of the baryonic composition, kinematics, and densities, the gas in the Galactic center is indistinguishable from high-redshift clouds and galaxies. As such, the Galactic center clouds may be used as a template to understand the evolution (and possibly the life cycle) of high-redshift clouds and galaxies.
Fossil galaxy groups are energetically and morphologically ideal environments to study the intergalactic medium (IGM) heating, because their inter-galactic gas is undisturbed due to the lack of recent group scale mergers. We study the role of active galactic nuclei (AGN) in heating the IGM in a sample of five fossil galaxy groups by employing properties at 610 MHz and 1.4 GHz. We find that two of the dominant galaxies in fossil groups, ESO 3060170 and RX J1416.4+2315, are associated with the radio lobes. We evaluate the PdV work of the radio lobes and their corresponding heating power and compare to the X-ray emission loss within cooling radius. Our results show that the power due to mechanical heating is not sufficiently high to suppress the cooling.