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We study the evolution of the MBH/Mhost relation up to z = 3 for a sample of 96 quasars with known host galaxy luminosities. Black hole masses are estimated assuming virial equilibrium in the broad-line regions, while the host galaxy masses are inferred from their luminosities. With this data, we are able to pin down the evolution of the MBH/Mhost relation over 85% of the age of the universe. While the MBH/Lhost relation remains nearly unchanged, taking into account the aging of the stellar population, we find that the MBH/Mhost ratio (Γ) increases by a factor ~ 7 from z = 0 to z = 3. We show that the evolution of Γ is independent of radio loudness and quasar luminosity. We propose that the most massive black holes, in their quasar phase at high-redshift, become extremely rare objects in host galaxies of similar mass in the local universe.
Feedback from AGN is a key component in most current models of galaxy formation and evolution. For the most massive galaxies, heating and removal of gas by the AGN could precipitate an abrupt quenching of star formation during a dramatic blow-out phase. The “smoking gun” for such a scenario would be direct evidence of powerful outflows associated with the jet. I present some preliminary results of a program to look for these in high-z radio galaxies (HzRGs). Recent observations of the z = 1.5 radio galaxy 3C 230 obtained with the NIFS integral-field spectrograph and Altair laser adaptive optics facility on Gemini North are shown. These reveal with unprecedented resolution the complex kinematics of this system in redshifted Hα and [N ii] emission. The bi-polar velocity field is aligned with the jet axis, with a kinematic center associated with the radio core itself, and turbulent edges approaching the galaxy's escape velocity. This suggests a gas mass of roughly 1011M⊙ has been propagating outwards for 107 to 108 years, corresponding to a mass loss of roughly 102–3M⊙ yr−1, based on its velocity and spatial extent. This is in good agreement with the energetics and typical ages of radio jets, and likely heralds the onset of the “red and dead” stage for this HzRG.
We present a large sample of X-ray selected type 2 QSOs from the XMM–COSMOS survey. Type 2 QSOs are luminous AGN whose central engines are obscured by large amounts of gas and dust. The selection criteria we have used are based on high X-ray luminosity (LX > 1044 erg s−1) and heavy obscuration (NH > 1022 cm−2). We derived stellar masses and star-formation rate estimates for the host galaxies from the best fit of the observed photometry. Type 2 QSOs are generally hosted in massive galaxies with on-going star formation.
Non-local thermodynamic equilibrium (NLTE) line formation for neutral and singly-ionized iron is considered through a range of stellar parameters characteristic of cool stars. A comprehensive model atom for Fe I and Fe II is presented. Our NLTE calculations support the earlier conclusions that the statistical equilibrium (SE) of Fe I shows an underpopulation of Fe I terms. However, the inclusion of the predicted high-excitation levels of Fe I in our model atom leads to a substantial decrease in the departures from LTE. As a test and first application of the Fe I/II model atom, iron abundances are determined for the Sun and four selected stars with well determined stellar parameters and high-quality observed spectra. Within the error bars, lines of Fe I and Fe II give consistent abundances for the Sun and two metal-poor stars when inelastic collisions with hydrogen atoms are taken into account in the SE calculations. For the close-to-solar metallicity stars Procyon and β Vir, the difference (Fe II - Fe I) is about 0.1 dex independent of the line formation model, either NLTE or LTE. We evaluate the influence of departures from LTE on Fe abundance and surface gravity determination for cool stars.
In this contribution, we estimate the temperature at the surface of known exoplanets and of their putative satellites for two albedo extreme cases (Venus and Mars) and present a selection of extremophiles living on Earth that can live under those conditions. We examine also the possibility of survival of microorganisms in planetary systems of variable stars.
Starburst features in the optical are nowadays well known, but the use of this knowledge is not always possible (e.g. objects heavily obscured). In this case the near-IR is of unprecedented value. Recent models show that TP-AGB stars should dominate the NIR spectra of populations 0.3 to 2 Gyr old. While the optical spectra is insensitive to the presence of these stars, the near-IR changes dramatically. Not only does the absolute flux in the near-IR is affected, but also peculiar absorption features appear. These features can be used as indicators of 1 Gyr stellar population. In this work we used the IRTF Spex to create the first empirical database of NIR spectra of carefully selected starbursts, to test for the first time and in a consistent way the new stellar population models that account for the TP-AGB. The methodology used is to do stellar population synthesis in the optical and in the NIR, and compare the predictions of both spectral regions. We also compare the strength of important features of the TP-AGB stars, like the CN (1.1 microns) and CO (2.3 microns) bands with optical diagnostics.
GALEV evolutionary synthesis models describe the evolution of stellar populations in general, of star clusters as well as of galaxies, both in terms of resolved stellar populations and of integrated light properties over cosmological timescales of >13 Gyr from the onset of star formation shortly after the Big Bang until today. A new web-interface now allows to run customized GALEV models with user-defined parameters. This web-interface, all data, and many more features to come, can be found at http://www.galev.org.
We have measured the probability distribution function of the ratio RX = log L1.4/LX, where L1.4/LX = ν Lν(1.4 GHz)/LX(2–10 keV), between the 1.4 GHz and the unabsorbed 2–10 keV luminosities and its dependence on LX and z. We have used a complete sample of ~1800 hard X-ray selected AGN, observed in the 1.4 GHz band, cross-correlated in order to exclude FR II-type objects, and thus obtain a contemporaneous measure of the radio and X-ray emission. The distribution P(RX|LX,z) is shown in Figure 1. Convolution of the distribution P(RX|LX,z) with the 2–10 keV X-ray AGN luminosity function from La Franca et al. (2005) and the relations between radio power and kinetic energy from Best et al. (2006) and Willott et al. (1999) allows us to derive the AGN kinetic power and its evolution. As shown in Figure 1, our results are in good agreement with the predictions of the most recent models of galaxy formation and evolution (e.g., Croton et al. 2006), where AGN radio feedback is required to quench the star formation.
In this work, we present the spectra of NGC 4151 observed over 11 years (from 1996 to 2006) using the SAO 6-m and 1-m telescopes (Russia), the GHAO 2.1-m telescope (Cananea, México), and the OAN-SPM 2.1-m telescope (San-Pedro, México). The procedure of spectra calibration is given by Shapovalova et al. (2008). Our analysis is focused on high-quality (S/N > 50) spectra of the Hα and Hβ emission lines.
We have identified a new class of object that we term PRONGS (powerful radio objects nested in galaxies with star formation). These are powerful radio sources whose optical properties are that of spiral/star-forming galaxies, unlike classic powerful radio sources which are typically hosted by elliptical galaxies in the local Universe. Here we present a first look at these enigmatic sources.
High-redshift quasars provide a unique glimpse into the early evolution of massive galaxies. The physical processes that trigger major bursts of star formation in quasar host galaxies (mergers and interactions) probably also funnel gas into the central regions to grow the super-massive black holes (SMBHs) and ignite the luminous quasar phenomenon. The globally dense environments where this occurs were probably also among the first to collapse and manufacture stars in significant numbers after the big bang. Measurements of the elemental abundances near quasars place important constraints on the nature, timing and extent of this star formation. A variety of studies using independent emission and absorption line diagnostics have shown that quasar environments have gas-phase metallicities that are typically a few times solar at all observed redshifts. These results are consistent with galaxy evolution scenarios in which large amounts of star formation (e.g., in the central regions) precede the visibly bright quasar phase. An observed trend for higher metallicities in more luminmous quasars (powered by more massive SMBHs) is probably tied to the well-known mass–metallicity relation among ordinary galaxies. This correlation and the absence of a trend with redshift indicate that mass is a more important parameter in the evolution than the time elapsed since the big bang.
TS01 is an exceptional planetary nebula (PN) in the Galactic halo: it is the most oxygen-poor and has a double-degenerate core with mass close to 1.4M⊙, possibly a Supernova Ia progenitor. With data from the far UV to the IR we can pin down the abundances of half a dozen of elements. The oxygen abundance is by 1.9(±0.3) dex lower than in the Sun. Standard AGB models with appropriate mass and metallicity cannot explain the observed chemical composition. We find that additional mixing, induced by stellar rotation and/or by the presence of the close companion can explain most of the features of the abundance pattern in TS01.
We present the observations of coronal hole that has originated at the polar hole in one hemisphere, extended to equatorial region, got disconnected and transported across the equator to polar region of opposite hemisphere.
The centers of most galaxies in the local Universe are occupied by compact, barely resolved sources. Based on their structural properties, position in the Fundamental Plane, and integrated spectra, these sources clearly have a stellar origin. They are therefore called ‘nuclear star clusters’ (NCs) or ‘stellar nuclei’. NCs are found in galaxies of all Hubble types, suggesting that their formation is intricately linked to galaxy evolution. Here, I review some recent studies of NCs, describe ideas for their formation and subsequent growth, and touch on their possible evolutionary connection with both supermassive black holes and globular clusters.
We present subarcsecond resolution mid-infrared (mid-IR) photometry in the range from 8 to 20 μm of 18 nearby Seyfert galaxies, reporting high spatial resolution nuclear fluxes for the entire sample (see Table 3 of Ramos Almeida et al. 2009). We construct spectral energy distributions (SEDs) that the AGN dominates, relatively uncontaminated by starlight, adding near-IR measurements from the literature at similar angular resolution. We find that the IR SEDs of intermediate-type Seyferts are flatter and present higher 10 to 18 μm ratios than those of Seyfert 2 (Sy2) galaxies.
We would like to know how molecular clouds turn into stellar clusters, and with what efficiency massive stars form in those clusters, since massive stars are the main agents responsible for evolution of the interstellar medium of galaxies, and their subsequent star-formation history. The imprint of ‘precluster’ molecular cloud conditions can be observed, but only in the least evolved, most embedded clusters, necessarily at wavelengths that can penetrate more than 10 visual magnitudes of extinction. Mid-infrared photometric imaging, most recently and extensively from Spitzer, can be used to select young stellar objects in clustered star-formation environments in our Galaxy and nearby galaxies. Relatively sophisticated methods have been developed, but the fundamental principle remains the selection of sources that have excess infrared emission from circumstellar dust. By fitting radiative-transfer models to a source's spectral-energy distribution between ~1 and ~100μm, we constrain the circumstellar dust distribution and evolutionary state. We can explore many things with this protostellar distribution in mass/luminosity and time/evolutionary state. For example we do not see strong evidence for primordial mass segregation in initial studies. We find evidence of primordial hierarchical substructure, greater clustering at the youngest stages, and even imprints of the pre-stellar Jeans scale. We see correlation of the youngest sources with dense molecular clumps and constrain the timescales for chemical processing and dispersal of those clumps. We have only begun to mine the wealth of existing Spitzer, emerging Herschel and soon ALMA data.
We present the initial results of a multiwavelength study to detect AGN in several galaxy clusters at moderate redshifts (0.5 < z < 0.9). By using multiple epochs of HST data, we identify 10–15 optically variable galactic nuclei in each cluster. The variable and non-variable galaxies are compared with X-ray point sources.
A key part of the modern-day regenerative solar magnetic dynamo is the reversal of the Sun's global magnetic field every eleven years. However, recent theoretical models indicate that young-rapidly rotating Sun-like stars may not always undergo full magnetic reversals, but instead may sometimes undergo “attempted” reversals where the magnetic field declines in strength only to return with the same polarity. Using the technique of Zeeman Doppler imaging we have mapped the magnetic field topology of a small sample of young Sun-like stars at multiple epochs, and present tentative evidence of an “attempted” magnetic field reversal on one of our stars.
The brilliant outcome of some 30 years of helioseismology spreads over a wide range of topics. Some highlights relevant to the cause of the solar activity cycle are listed up. The rotation profile in the solar convective zone is discussed as an important source of the dynamo mechanism. The kinematic dynamo model is described in the linear approximation, and the condition for the solar type dynamo is derived. It is shown that comparison of this condition with the rotation profile determined from helioseismology is useful to identify the possible seats of the dynamo.