Irene Cruz-Gonzalez

THE HOST-GALAXY OF THE GAMMA-RAY NARROW-LINE SEYFERT 1 GALAXY 1H 0323+342

We present optical and near-infrared (NIR) imaging data of the radio-loud, narrow-line Seyfert 1 galaxy 1H 0323+342, which shows intense and variable gamma-ray activity discovered by the Fermi satellite with the Large Area Telescope. Near-infrared and optical images are used to investigate the structural properties of the host galaxy of 1H 0323+342; this together with optical spectroscopy allows us to examine its black hole mass. Based on two-dimensional (2D) multiwavelength surface-brightness modeling, we find that statistically, the best model fit is a combination of a nuclear component and a Sersic profile (n ∼ 2.8). However, the presence of a disk component (with a small bulge n ∼ 1.2) also remains a possibility and cannot be ruled out with the present data. Although at first glance a spiral-arm-like structure is revealed in our images, a 2D Fourier analysis of the imagery suggests that this structure corresponds to an asymmetric ring, likely associated with a recent violent dynamical interaction. We discuss our results in the context of relativistic jet production and galaxy evolution.

Destruction of the Environment of the BN-KL Nebula

Resumen en: We present the velocity structure of the 2.12 micron H2 emission in Orion, obtained with an IR Fabry-Perot interferometer with a spectral resolution of 2...

A study of the stellar population in the Lynds 1641 dark cloud. I - The IRAS catalog sources

The character of the sources identified in the IRAS Point Source Catalog and located within the boundaries of the nearest giant molecular cloud, Lynds 1641 is discussed. New optical and near-infrared photometry are combined to provide spectral energy distributions (SEDs) for these objects divided into three classes: class I objects with flat or rising spectra, class II objects with spectra intermediate in slope between a flat and blackbody spectrum, and class III objects with spectra similar to those of blackbodies. It is found that L1641 contains a much larger percentage of class I sources than does the nearby Taurus-Auriga star-forming complex. Spectral energy distributions for the IRAS-selected sample are examined and compared with SEDs for young stellar objects (YSOs) located in Taurus-Auriga. The IRAS-selected sources having optical counterparts in the H-R diagram are identified and discussed along with the distribution of masses and ages for these YSOs.

The isolated interacting galaxy pair NGC 5426/27 (Arp 271)

We present H alpha observations of the isolated interacting galaxy pair NGC 5426/27 using the scanning Fabry-Perot interferometer PUMA. The velocity field, various kinematical parameters and rotation curve for each galaxy were derived. The FWHM map and the residual velocities map were also computed to study the role of non-circular motions of the gas. Most of these motions can be associated with the presence of spiral arms and structure such as central bars. We found a small bar-like structure in NGC 5426, a distorted velocity field for NGC 5427 and a bridge-like feature between both galaxies which seems to be associated with NGC 5426. Using the observed rotation curves, a range of possible masses was computed for each galaxy. These were compared with the orbital mass of the pair derived from the relative motion of the participants. The rotation curve of each galaxy was also used to fit different mass distribution models considering the most common theoretical dark halo models. An analysis of the interaction process is presented and a possible 3D scenario for this encounter is also suggested.

A study of the stellar population in the Lynds 1641 dark cloud. IV. The Einstein X-ray sources

The properties of 65 X-ray sources identified on four overlapping Einstein IPC frames in the northern portion of the L1641 giant molecular cloud are discussed. The X-ray sources have ages ranging from 300,000 to 10 million yr, extending to considerably greater ages than the IRS sample. Examination of X-ray luminosities leads to the conclusion that L(x) is proportional to the surface area of the star; comparison with the Extended Medium Sensitivity Survey sample shows that the premain-sequence stars form an extension of the relationship found by Fleming et al. (1989) for late-type main-sequence stars with an upper envelope determined by coronal saturation. No evidence is found in this sample to support the proposal that X-ray emission is quenched by circumstellar gas ejected by the more extreme T Tauri stars. 100 refs.

Kinematics of the Molecular Hydrogen from the Planetary Nebula NGC 2346

We present scanning Fabry-Perot observations of the planetary nebula NGC 2346 at the near-infrared vibrationally excited line H2 S(1) 1–0 at 2.122 μm. The kinematics matches a model of two ellipsoids with an outflow velocity proportional to the distance of the gas from the central star and moving radially outward. The stronger emission is located in an equatorial torus expanding at 16 km s-1. It is likely that a shock between 6 and 16 km s-1, depending on the assumed velocity of the red giant envelope (0 to 10 km s-1), excites the molecular gas. Depending on those limiting values for the shock velocity, the density of the preshock gas falls in the range (0.3–1.7) × 104 cm-3, and consequently the mass of the molecular gas in the nebula is estimated to be between 0.34 and 1.85 M⊙, much larger than the mass of the ionized gas, and marginally in agreement with the estimate coming from CO observations alone.

Radio-optical scrutiny of compact AGN: correlations between properties of pc-scale jets and optical nuclear emission

Aims. We study the correlations between the VLBA (Very Long Baseline Array) radio emission at 15 GHz, extended emission at 151 MHz, and optical nuclear emission at 5100 A for a complete sample of 135 compact jets. Methods. We use the partial Kendalls tau correlation analysis to check the link between radio properties of parsec-scale jets and optical nuclear luminosities of host active galactic nuclei (AGN). Results. We find a significant positive correlation for 99 quasars between optical nuclear luminosities and total radio (VLBA) luminosities of unresolved cores at 15 GHz originated at milliarcseconds scales. For 18 BL Lacs, the optical continuum emission correlates with the radio emission of the jet at 15 GHz. We suggest that the radio and optical emission are beamed and originate in the innermost part of the sub-parsec-scale jet in quasars. Analysis of the relation between the apparent speed of the jet and the optical nuclear luminosity at 5100 A supports the relativistic beaming model for the optical emission generated in the jet, and allows the peak values of the intrinsic optical luminosity of the jet and its Lorentz factor to be estimated for the populations of quasars (2 x 10 20 W Hz -1 and γ = 52), BL Lacs (9 x 10 21 W Hz -1 and y = 20), and radio galaxies (1.5 x 10 21 W Hz -1 and γ = 9). The radio-loudness of quasars (the ratio of 15 GHz flux density and optical nuclear flux at 5100 A) is found to increase at high redshifts, which is interpreted as progressively higher Doppler factors in radio regime compared to those in optical. A strong positive correlation is found between the intrinsic kinetic power of the jet (measured from the flux density at 151 MHz) and the apparent luminosities of the total and the unresolved core emission of the jet at 15 GHz. This correlation is interpreted in terms of an intrinsically more luminous parsec-scale jet producing more luminous extended structure, which is detectable at low radio frequencies, 151 MHz. A possibility that the low frequency radio emission is relativistically beamed in superluminal sources and therefore correlates with radio luminosity of the jet at 15 GHz cannot be ruled out. Monitoring of superluminal AGN in a wide range of frequencies is required to check the contribution of each effect.

A Multiwavelength Study of Narrow-Line Seyfert 1 Galaxies from the Second Byurakan Survey

In this work we present a multiwavelength study of narrow-line Seyfert 1 galaxies (NLS1s) discovered in the Second Byurakan Survey (SBS). The sample consists of 26 objects, which have MB ≥ -23.0, or -19.9 > MB > -23.0, 0.0243 1). The traditional linear correlation LX and Lop, which seems to hold for active galactic nuclei in general, is found for SBS NLS1s. An anticorrelation between the FWHM of Hβ and the ratio of Fe II λ4570/Hβ is also observed. A weak correlation is found between αox slope and Lop. One of our main findings is that almost all SBS NLS1s may not have an FIR bump. Their spectral energy distribution suggests that they may also possess a big blue bump. The absence of an IR bump in most SBS NLS1s and the weakness of X-ray radiation in some of them may argue against the presence of a broad-line region. The surface density of SBS NLS1s is less than 0.015 deg-2 (B < 17.5,z < 0.16).

Molecular Hydrogen Kinematics in Cepheus A

We present the radial velocity structure of the molecular hydrogen outflows associated with the star-forming region Cepheus A. This structure is derived from the Doppler shift of the H2 v = 1–0 S(1) emission line obtained by Fabry-Perot spectroscopy. The east and west regions of emission, called Cep A (E) and Cep A (W), show radial velocities in the range of -20 to 0 km s-1 with respect to the molecular cloud. Cep A (W) shows an increasing velocity with position offset from the core, indicating the existence of a possible accelerating mechanism. Cep A (E) has an almost constant mean radial velocity of -18 km s-1 along the region, although with a large dispersion in velocity, indicating the possibility of a turbulent outflow. A detailed analysis of the Cep A (E) region shows evidence for the presence of a Mach disk on that outflow. In addition, we argue that the presence of a velocity gradient in Cep A (W) is indicative of a C-shock in this region. Following Riera and coworkers, we analyzed the data using wavelet analysis to study the line width and central radial velocity distributions. We found that both outflows have complex spatial and velocity structure characteristic of a turbulent flow.

Flux-Velocity Relation for H2 Outflows*

We present an analysis of velocity-resolved near-IR molecular hydrogen observations of a variety of protostellar outflows with very different energetics, degrees of collimation, and morphologies. Observations in the 2.12 μm line of H2 were obtained using an IR Fabry-Perot interferometer with a spectral resolution of 23 km s-1. The integrated flux-velocity diagrams for each outflow show a flat spectrum for low velocities followed by a decreasing power law dF/dv ∝ vγ, with γ between -1.8 and -2.6, for velocities higher than a clearly defined break velocity at 2-17 km s-1. Contrary to shock model predictions, it is shown that the H2 intensity is constant with velocity. We argue that the flux-velocity relation can then be interpreted as a mass-velocity relation, in striking similarity to the power-law mass spectra observed in CO outflows. By comparing H2 and CO mass-velocity spectra, it is shown that there is a velocity regime in which both molecules coexist and produce similar γ-values. Evolution effects in outflows appear as a correlation between outflow length and γ; as outflows age, the spectra becomes steeper. Our results support a common physical origin for both CO and H2 emission and a strong association between the molecular outflows traced in each molecule.