New CO and Millimeter Continuum Observations of the z=2.394 Radio Galaxy 53W002

The z=2.39 radio galaxy 53W002 lies in a cluster of Ly-alpha emission line objects and may itself be undergoing a major burst of star formation. CO(3--2) emission, at 102 GHz, was detected from 53W002 by Scoville et al. (1997a), who also reported a possible 30 kpc extension and velocity gradient suggesting a rotating gaseous disk. In this paper we present new interferometric CO(3--2) observations which confirm the previous line detection with improved signal-to-noise ratio, but show no evidence for source extension or velocity gradient. The compact nature of the CO source and the molecular mass found in this object are similar to luminous infrared galaxies and other AGNs previously studied

Detection of CO(3-2) Emission at z=2.64 from the Gravitationally Lensed Quasar MG 0414+0534

We have detected CO(3-2) line emission from the gravitationally lensed quasar MG 0414+0534 at redshift 2.64, using the IRAM Plateau de Bure Interferometer. The line is broad, with Delta v_FWHM = 580 km/s. The velocity-integrated CO flux is comparable to, but somewhat smaller than, that of IRAS F10214+4724 and the Cloverleaf quasar (H1413+117), both of which are at similar redshifts. The lensed components A1+A2 and B were resolved, and separate spectra are presented for each. We also observed the unlensed radio quiet quasar PG 1634+706 at z=1.33, finding no significant CO emission.Comment: To be published in ApJ Letters. 9 pages of text in Latex, using style file aaspp4.sty (included), plus two ps figures to be printed separatel

The stellar content of giant H II regions in NGC 7714

This is an electronic version of an article published in The Astrophysical Journal. García-Vargas, M.L., González-Delgado, R.M., Pérez, E., Alloin, D., Díaz, A. and E. Terlevich. The stellar content of giant H II regions in NGC 7714. The Astrophysical Journal 478 (1997): 112-12

The near-IR luminosity-metallicity relation of dwarf irregular galaxies

We report on the recent developments of our long-term investigation of the near-IR luminosity-metallicity relation for dwarf irregular galaxies in nearby groups. A very well-defined relation is emerging from our observational database, and a preliminary discussion of its implications is given.Comment: 5 pages, 3 figures, to be published in the IAU Coll. 198, "Near-Field Cosmology With Dwarf Elliptical Galaxies", ed. B. Binggeli and H. Jerje

Massive Clusters in the Inner Regions of NGC 1365: Cluster Formation and Gas Dynamics in Galactic Bars

Cluster formation and gas dynamics in the central regions of barred galaxies are not well understood. This paper reviews the environment of three 10^7 Msun clusters near the inner Lindblad resonance of the barred spiral NGC 1365. The morphology, mass, and flow of HI and CO gas in the spiral and barred regions are examined for evidence of the location and mechanism of cluster formation. The accretion rate is compared with the star formation rate to infer the lifetime of the starburst. The gas appears to move from inside corotation in the spiral region to looping filaments in the interbar region at a rate of ~6 Msun/yr before impacting the bar dustlane somewhere along its length. The gas in this dustlane moves inward, growing in flux as a result of the accretion to ~40 Msun/yr near the ILR. This inner rate exceeds the current nuclear star formation rate by a factor of 4, suggesting continued buildup of nuclear mass for another ~0.5 Gyr. The bar may be only 1-2 Gyr old. Extrapolating the bar flow back in time, we infer that the clusters formed in the bar dustlane outside the central dust ring at a position where an interbar filament currently impacts the lane. The ram pressure from this impact is comparable to the pressure in the bar dustlane, and both are comparable to the pressure in the massive clusters. Impact triggering is suggested. The isothermal assumption in numerical simulations seems inappropriate for the rare fraction parts of spiral and bar gas flows. The clusters have enough lower-mass counterparts to suggest they are part of a normal power law mass distribution. Gas trapping in the most massive clusters could explain their [NeII] emission, which is not evident from the lower-mass clusters nearby.Comment: 21 pages, 4 figures, accepted by ApJ, 702, September 2009, revision adds reference

Re-examining High Abundance SDSS Mass-Metallicity Outliers: High N/O, Evolved Wolf-Rayet Galaxies?

We present new MMT spectroscopic observations of four dwarf galaxies representative of a larger sample observed by the Sloan Digital Sky Survey (SDSS) and identified by Peeples et al. (2008) as low-mass, high oxygen abundance outliers from the mass-metallicity relation. Peeples et al. (2008) showed that these four objects (with metallicity estimates of 8.5 =< 12 + log(O/H) =< 8.8) have oxygen abundance offsets of 0.4-0.6 dex from the M_B luminosity-metallicity relation. Our new observations extend the wavelength coverage to include the [OII] 3726,3729 doublet, which adds leverage in oxygen abundance estimates and allows measurements of N/O ratios. All four spectra are low excitation, with relatively high N/O ratios (N/O >~ 0.10), each of which tend to bias estimates based on strong emission lines toward high oxygen abundances. These spectra all fall in a regime where the "standard" strong line methods for metallicity determinations are not well calibrated either empirically or by photoionization modeling. By comparing our spectra directly to photoionization models, we estimate oxygen abundances in the range of 7.9 =< 12 + log(O/H) =< 8.4, consistent with the scatter of the mass-metallicity relation. We discuss the physical nature of these galaxies that leads to their unusual spectra (and previous classification as outliers), finding their low excitation, elevated N/O, and strong Balmer absorption are consistent with the properties expected from galaxies evolving past the "Wolf-Rayet galaxy" phase. We compare our results to the "main" sample of Peeples et al. (2008) and conclude that they are outliers primarily due to enrichment of nitrogen relative to oxygen, and not due to unusually high oxygen abundances for their masses or luminosities.Comment: 38 pages, 10 figures, accepted to Ap

Hubble Space Telescope Ultraviolet Spectroscopy of Fourteen Low-Redshift Quasars

We present low-resolution ultraviolet spectra of 14 low redshift (z<0.8) quasars observed with HST/STIS as part of a Snap project to understand the relationship between quasar outflows and luminosity. By design, all observations cover the CIV emission line. Nine of the quasars are from the Hamburg-ESO catalog, three are from the Palomar-Green catalog, and one is from the Parkes catalog. The sample contains a few interesting quasars including two broad absorption line (BAL) quasars (HE0143-3535, HE0436-2614), one quasar with a mini-BAL (HE1105-0746), and one quasar with associated narrow absorption (HE0409-5004). These BAL quasars are among the brightest known (though not the most luminous) since they lie at z<0.8. We compare the properties of these BAL quasars to the z1.4 Large Bright Quasar samples. By design, our objects sample luminosities in between these two surveys, and our four absorbed objects are consistent with the v ~ L^0.62 relation derived by Laor & Brandt (2002). Another quasar, HE0441-2826, contains extremely weak emission lines and our spectrum is consistent with a simple power-law continuum. The quasar is radio-loud, but has a steep spectral index and a lobe-dominated morphology, which argues against it being a blazar. The unusual spectrum of this quasar resembles the spectra of the quasars PG1407+265, SDSSJ1136+0242, and PKS1004+13 for which several possible explanations have been entertained.Comment: Uses aastex.cls, 21 pages in preprint mode, including 6 figures and 2 tables; accepted for publication in The Astronomical Journal (projected vol 133

The XMM-LSS survey. Survey design and first results

We have designed a medium deep large area X-ray survey with XMM - the XMM Large Scale Structure survey, XMM-LSS - with the scope of extending the cosmological tests attempted using ROSAT cluster samples to two redshift bins between 0<z<1 while maintaining the precision of earlier studies. Two main goals have constrained the survey design: the evolutionary study of the cluster-cluster correlation function and of the cluster number density. The results are promising and, so far, in accordance with our predictions as to the survey sensitivity and cluster number density. The feasibility of the programme is demonstrated and further X-ray coverage is awaited in order to proceed with a truly significant statistical analysis. (Abridged)Comment: Published in Journal of Cosmology and Astroparticle Physic

Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. 5: Variability of the ultraviolet continuum and emission lines of NGC 3783

We report on the results of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of 7 months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variability was observed in both continuum and emission-line fluxes. The light curves for the continuum fluxes exhibited two well-defined local minima or 'dips,' the first lasting is less than or approximately 20 days and the second is less than or approximately 4 days, with additional episodes of relatively rapid flickering of approximately the same amplitude. As in the case of NGC 5548 (the only other Seyfert galaxy that has been the subject of such an intensive, sustained monitoring effort), the largest continuum variations were seen at the shortest wavelengths, so that the continuum became 'harder' when brighter. The variations in the continuum occurred simultaneously at all wavelengths (delta(t) is less than 2 days). Generally, the amplitude of variability of the emission lines was lower than (or comparable to) that of the continuum. Apart from Mg II (which varied little) and N V (which is relatively weak and badly blended with Ly(alpha), the light curves of the emission lines are very similar to the continuum light curves, in each case with a small systematic delay or 'lag.' As for NGC 5548, the highest ionization lines seem to respond with shorter lags than the lower ionization lines. The lags found for NGC 3783 are considerably shorter than those obtained for NGC 5548, with values of (formally) approximately 0 days for He II + O III), and approximately 4 days for Ly(alpha) and C IV. The data further suggest lags of approximately 4 days for Si IV + O IV) and 8-30 days for Si III + C III). Mg II lagged the 1460 A continuum by approximately 9 days, although this result depends on the method of measuring the line flux and may in fact be due to variability of the underlying Fe II lines. Correlation analysis further shows that the power density spectrum contains substantial unresolved power over timescales of is less than or approximately 2 days, and that the character of the continuum variability may change with time