arXiv subjects

W. Jaffe

Publications and source records attributed to W. Jaffe.

45 records · Page 3Linked to original sources

arXiv2005

HII and H2 in the envelopes of cooling flow central galaxies

We report observations of ionized and warm molecular gas in the extended regions of the central galaxies in several cooling flow clusters. These show that both gas phases are present in these clusters to large radii. We trace both Pa alpha and H2 lines to radii in excess of 20 kpc. The surface brightness profiles of the two phases trace each other closely. Apart from very close to the central AGN, line ratios in and between the phases vary only slowly with position. The kinematics of the phases are indistinguishable and away from the influence of the central AGN both the mean and dispersion in velocity are low (<= 100 km/s) ruling out kinematic support of the molecular gas. All of the above indicates that the mechanisms for heating the molecular gas and ionizing the HII regions are highly coupled. The highest surface brightness emission within a few kpc of the central AGN is distinct, both kinematically and thermally from that at larger radii. The relative strengths of the Pa alpha to the H2 lines indicates a source of UV excitation rich in EUV relative to FUV photons, e.g. a black body with a temperature >= 10^5 K.

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arXiv2005

The Mid-IR spatially resolved environment of OH26.5+0.6 at maximum luminosity

We present observations of the famous OH/IR star OH26.5+0.6 obtained using the Mid-Infrared Interferometric Instrument MIDI at the European Southern Observatory (ESO) Very Large Telescope Interferometer VLTI. The emission of the dusty envelope, spectrally dispersed at a resolution of 30 from 8 to 13.5 micron, appears resolved by a single dish UT telescope. In particular the angular diameter increases strongly within the silicate absorption band. Moreover an acquisition image taken at 8.7 micron exhibits, after deconvolution, a strong asymmetry. The axis ratio is 0.75+/-0.07 with the FWHM of the major and minor axis which are 286mas and 214mas respectively. The measured PA angle, 95 degrees +/-6 degrees is reminiscent of the asymmetry in the OH maser emission detected at 1612MHz by Bowers & Johnston (1990) for this star. In interferometric mode the UT1-UT3 102m baseline was employed to detect the presence of the star. No fringes have been found with a detection threshold estimated to be of the order of 1% of the total flux of the source, i.e. 5-8 Jy. These observations were carried out during the phase of maximum luminosity of the star, when the dust shell is more diluted and therefore the chance to detect the central source maximized. We modeled the dusty environment based on the work of Justannont et al. (1996). In particular, the failure to detect fringes provides strong constraints on the opacities in the inner regions of the dust shell or in the close vicinity of the star.

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arXiv2005

The sub-arcsecond dusty environment of Eta Carinae

The core of the nebula surrounding Eta Carinae has been observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to constrain spatially and spectrally the warm dusty environment and the central object. In particular, narrow-band images at 3.74 and 4.05 micron reveal the butterfly shaped dusty environment close to the central star with unprecedented spatial resolution. A void whose radius corresponds to the expected sublimation radius has been discovered around the central source. Fringes have been obtained in the Mid-IR which reveal a correlated flux of about 100Jy situated 0.3" south-east of the photocenter of the nebula at 8.7 micron, which corresponds with the location of the star as seen in other wavelengths. This correlated flux is partly attributed to the central object, and these observations provide an upper limit for the SED of the central source from 2.2 to 13.5 micron. Moreover, we have been able to spectrally disperse the signal from the nebula itself at PA=318 degree, i.e. in the direction of the bipolar nebula 310 degree) within the MIDI field of view of 3". A large amount of corundum (Al2O3) is discovered, peaking at 0.6-1.2" south-east from the star, whereas the dust content of the Weigelt blobs is dominated b silicates. We discuss the mechanisms of dust formation which are closely related to the geometry of this Butterfly nebulae.

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arXiv2003

A Submillimetre Selected Quasar in the Field of Abell478

We present the discovery of a dusty quasar, SMMJ04135+10277, located behind the galaxy cluster Abell 478. The quasar was discovered as the brightest source in a submillimetre survey of high redshift galaxies lensed by foreground rich clusters of galaxies in a project aimed at studying the cosmic star formation history of dusty galaxies. With submm fluxes of S_850 = 25+-2.8 mJy and S_450 = 55+-17 mJy this object is one of the brightest submillimetre sources known. Optical observations revealed a quasar with redshift z=2.837. The quasar was also detected at shorter infrared wavelengths with the Infrared Space Observatory. This object is the first quasar discovered by its submm emission. Given the general lack of overlap between deep submm and X-ray samples, usually interpreted as a low incidence of active nuclei in submm samples, this is an unusual object. Analysis of number counts of quasars and of submm galaxies bears out this suggestion. We compare the properties of SMMJ04135+10277 to those of optically selected quasars with submm emission, and argue that the optical faintness results from a large viewing angle with the direction of relativistic beaming, and not from abnormally high extinction. We also find indications that the bulk of the submm flux density is not powered by the quasar nucleus. This conclusion is supported by analysis of the infrared spectral energy distribution. These results are consistent with previous observations that quasars at higher redshift tend to have a more prominent cold dust component, most likely powered by extended star formation in the host galaxy. The quasar is found to have a total infrared luminosity of (2.9+-0.5)x10^13 L_sun, dominated by the emission from cool dust. (Abridged)

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arXiv2001

Dusty Nuclear Disks and Filaments in Early Type Galaxies

We examine the dust properties of a nearby distance-limited sample of early type galaxies using the WFPC2 of the Hubble Space Telescope. Dust is detected in 29 out of 67 galaxies (43%), including 12 with small nuclear dusty disks. In a separate sample of 40 galaxies biased for the detection of dust by virtue of their detection in the IRAS 100 micron band, dust is found in ~78% of the galaxies, 15 of which contain dusty disks. In those galaxies with detectable dust, the apparent mass of the dust correlates with radio and far infrared luminosity, becoming more significant for systems with filamentary dust. A majority of IRAS and radio detections are also associated with dusty galaxies rather than dustless galaxies. This indicates that thermal emission from clumpy, filamentary dust is the main source of the far-IR radiation in early type galaxies. Dust in small disk-like morphology tends to be well aligned with the major axis of the host galaxies, while filamentary dust appears to be more randomly distributed with no preference for alignment with any major galactic structure. This suggests that, if the dusty disks and filaments have a common origin, the dust originates externally and requires time to dynamically relax and settle in the galaxy potential in the form of compact disks. More galaxies with visible dust than without dust display emission lines, indicative of ionized gas, although such nuclear activity does not show a preference for dusty disk over filamentary dust. There appears to be a weak relationship between the mass of the dusty disks and central velocity dispersion of the galaxy, suggesting a connection with a similar recently recognized relationship between the latter and the black hole mass.

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arXiv2000

Infrared Spectra of Cooling Flow Galaxies

We have taken K-band spectra covering 7 cooling flow clusters. The spectra show many of the 1-0S transitions of molecular Hydrogen, as well as some of the higher vibrational transitions, and some lines of ionized Hydrogen. The line ratios allow us to conclude that the rotational states of the first excited vibrational state are in approximate LTE, so that densities above 10^5/ cm^3 are likely, but there is evidence that the higher vibrational states are not in LTE. The lack of pressure balance between the molecular gas and the ionized components emphasizes the need for dynamic models of the gas. The ratios of the ionized to molecular lines are relatively constant but lower than from starburst regions, indicating that alternative heating mechanisms are necessary.

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arXiv2000

A Submillimeter Selected Quasar in the Field of Abell 478

We report the discovery of a z=2.83 quasar in the field of the cooling flow galaxy cluster Abell 478. This quasar was first detected in a submm survey of star forming galaxies at high redshifts, as the brightest source. We discuss the optical spectrum and far-IR spectral energy distribution (SED) of this object.

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arXiv1999

A Thin HI Circumnuclear Disk in NGC4261

We report on high sensitivity, spectral line VLBI observations of the HI absorption feature in the radio galaxy NGC4261. Although absorption is only detectable on the most sensitive baseline, it can be unambiguously associated with the counterjet and is interpreted to originate in a thin atomic circumnuclear disk. This structure is probably a continuation of the dusty accretion disk inferred from HST imaging, which could be feeding the massive black hole. HI column densities in front of the counterjet of the order of 10^{21}(T_sp/100 K) cm^{-2} are derived, consistent with X-ray data and VLBI scale free-free absorption. The data presented here are the result of the first scientific project processed on the new EVN MkIV data processor.

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arXiv1997

HST Detections of Massive Black Holes in the Centers of Galaxies

After correcting spherical aberration in the Hubble Space Telescope in 1993, the central masses of galaxies can be measured with a resolution 5 to 10 times better than can be achieved at the best terrestrial sites. This improvement in resolution is decisive for detecting the gravitational signature of massive black holes in galaxy nuclei. The discovery of small (r ~ 100-200 pc) rotating gaseous and stellar disks in the centers of many early-type galaxies provides a new and efficient means for measuring the central potentials of galaxies. Concomitantly, VLBI observations of water masers in the nuclei of NGC 4258 and NGC 1068 revealed exquisite Keplerian rotation curves around massive black holes at radii as small as 0.1 pc. Recent terrestrial K-band measurements of the proper motions of stars in the cluster at the center of the Galaxy provide irrefutable evidence for a black hole with a mass of 2.7E+6 M_sun. At the time of this symposium, the presence of central massive black holes has been established in 12 galaxies. The evidence suggests that there are massive black holes in the centers of all AGNs and in most, if not all, nucleated galaxies. The present data show at best a weak correlation between black hole mass and bulge luminosity.

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