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Lonsdale, Carol J.

Publications and source records attributed to Lonsdale, Carol J..

18 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

The First Hyper-Luminous Infrared Galaxy Discovered by WISE

We report the discovery by the Wide-field Infrared Survey Explorer of the z = 2.452 source WISEJ181417.29+341224.9, the first hyperluminous source found in the WISE survey. WISE 1814+3412 is also the prototype for an all-sky sample of approximately 1000 extremely luminous "W1W2-dropouts" (sources faint or undetected by WISE at 3.4 and 4.6 micrometers and well detected at 12 or 22 micrometers). The WISE data and a 350 micrometers detection give a minimum bolometric luminosity of 3.7 x 10(exp 13) solar luminosity, with approximately 10(exp 14) solar luminosity plausible. Followup images reveal four nearby sources: a QSO and two Lyman Break Galaxies (LBGs) at z = 2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission. Gravitational lensing is unlikely given the source locations and their different spectra and colors. The dominant LBG spectrum indicates a star formation rate approximately 300 solar mass yr(exp -1), accounting for less than or equal to 10 percent of the bolometric luminosity. Strong 22 micrometer emission relative to 350 micrometer implies that warm dust contributes significantly to the luminosity, while cooler dust normally associated with starbursts is constrained by an upper limit at 1.1 mm. Radio emission is approximately 10? above the far-infrared/radio correlation, indicating an active galactic nucleus is present. An obscured AGN combined with starburst and evolved stellar components can account for the observations. If the black hole mass follows the local MBH-bulge mass relation, the implied Eddington ratio is approximately greater than 4. WISE 1814+3412 may be a heavily obscured object where the peak AGN activity occurred prior to the peak era of star formation.

Eisenhardt, Peter R.↗
NASA NTRS1997

Symmetric Parsec-scale OH Megamaser Structures in Arp 220

The parsec-scale OH megamaser emission in the luminous IR galaxy Arp 200 has been imaged in detail using global VLBI array. Four major emission regions are revelaed inthe 1667 MHz line, each with complex spatial and velocity structure showing intriguing symmetries.

parsec-scale galaxies infrared radio lines masers↗
NASA NTRS1997

Symmetric Parsec-scale OH Megamaser Structure in Arp 220

The parsec-scale OH megamaser emission in the luminous IR galaxy Arp 220 has been imaged in detail using a global VLBI array. Four major emission regions are revealed in the 1667 MHz line, each with complex spatial and velocity structure showing intriguing symmetries.

active infrared radio lines galaxies maser↗
NASA NTRS1995

Ultraluminous infrared galaxies and the radio-optical correlation for quasars

Through analysis of available optical spectrophotometric data and radio flux density measurements in the literature, it is demonstrated that a good correlation exists between the radio power and bolometric luminosity of the optically-selected OSOs in the Bright Quasar Sample (BOS) of Schmidt and Green (1983). We have recently used VLBI measurements of a sample of ultraluminous infrared galaxies to infer the likely existence of radio-quiet Active Galactic Nuclei (AGNs) deeply enshrouded in dust within their nuclei (Lonsdale, Smith, and Lonsdale 1993). We employ the radio-bolometric luminosity correlation for the BQS quasars to test whether these hypothetical buried AGNs can be energetically responsible for the observed far-infrared luminosities of the ultraluminous infrared galaxies. The ultraluminous infrared galaxies are shown to follow the same relation between radio core power and bolometric luminosity as the radio-quiet QSOs, suggesting that buried AGNs can account for essentially all the observed infrared luminosity, and raising the possibility that any starburst which may be in progress may not be energetically dominant. The broader implications of the radio-optical correlation in quasars for AGNs and luminous infrared galaxy models and the use of radio astronomy as a probe of the central powerhouse in radio quiet AGNs and luminous infrared galaxies are briefly discussed.

Lonsdale, Carol J.↗
NASA NTRS1994

Simulations of deep galaxy fields. 1: Monte Carlo simulations of optical and near-infrared counts

Monte Carlo simulations of three-dimensional galaxy distributions are performed, following the 1988 prescription of Chokshi & Wright, to study the photometric properties of evolving galaxy populations in the optical and near-infrared bands to high redshifts. In this paper, the first of a series, we present our baseline model in which galaxy numbers are conserved, and in which no explicit 'starburst' population is included. We use the model in an attempt to simultaneously fit published blue and near-infrared photometric and spectroscopic observations of deep fields. We find that our baseline models, with a formation redshift, z(sub f), of 1000, and H(sub 0) = 50, are able to reproduce the blue counts to b(sub j) = 22, independent of the value of Omega(sub 0), and also to provide a satisfactory fit to the observed blue-band redshift distributions, but for no value of Omega(sub 0) do we achieve an acceptable fit to the fainter blue counts. In the K band, we fit the number counts to the limit of the present-day surveys only for an Omega(sub 0) = 0 cosmology. We investigate the effect on the model fits of varying the cosmological parameters H(sub 0), the formation red-shift z(sub f), and the local luminosity function. Changing H(sub 0) does not improve the fits to the observations. However, reducing the epoch of a galaxy formation used in our simulations has a substantial effect. In particular, a model with z(sub f) approximately equal to 5 in a low Omega(sub 0) universe improves the fit to the faintest photometric blue data without any need to invoke a new population of galaxies, substantial merging, or a significant starburst galaxy population. For an Omega(sub 0) = 1 universe, however, reducing z(sub f) is less successful at fitting the blue-band counts and has little effect at all at K. Varying the parameters of the local luminosity function can also have a significant effect. In particular the steep low end slope of the local luminosity function of Franceschini et al. allows an acceptable fit to the b(sub j) less than or equal to 25 counts for Omega(sub 0) = 1, but is incompatible with Omega(sub 0) = 0.

Chokshi, Arati↗
NASA NTRS1993

Simulations of Deep Galaxy Fields I: Monte-Carlo Simulations of Optical and Near Infrared Counts

Monte-Carlo simulations of three dimensional galaxy distributions are performed, following the prescription of Chokishi & Wright (1988), to study the photometric properties of evolving galaxy populations in the optical and near infrared bands to high redshifts. Galaxies are spatially distributed according to the spatial two point correlation function in a range of cluster to field environments andin volume elements appropriate to the cosmological model under consideration. Details of individual galaxy properties, including luminosities, morphologies, disk-to-bulge ratios, and size distributions are simulated to match local observed galaxy properties. Galaxies have evolving gas fraction, metallicity and spectral energy distributions that include both stellar emission and internal dust absorption and re-emission. The simulations result in noiseless two dimensional galaxy distributions on the sky that canbe compared to the observed deep images in the blue and near-infrared bands...

faint↗
NASA NTRS1993

The Infrared Background: Theory

The infrared region of the spectrum is a very interesting and important one for the study of extragalactic backgrounds, both galaxian and pre-galactic. This review concentrates on backgrounds from protogalaxies and galaxies. Detailed discussions of many possible pre-galactic backgrounds have recently been presented by Bond, Carr and Hogan (1986, 1991); see Carr (1992) for a recent review of these and Wright et al. (1993) for a summary of how well some of them have fared in light of the most recent COBE observational results. I will concentrate on the approximate wavelength range 10 to 500 micrometers since both the near-infrared and the submillimeter range are discussed by others...

Lonsdale, Carol J.↗
NASA NTRS1993

Evolution of the Blue and Far-Infrared Galaxy Luminosity Functions

The space density of blue-selected galaxies at moderate redshifts is determined here directly by deriving the luminosity function. Evidence is found for density evolution for moderate luminosity galaxies at a rate of (1+z) exp delta, with a best fit of delta + 4 +/- 2, between the current epoch and Z greater than about 0.1. At M(b) less than -22 evidence is found for about 0.5-1.5 mag of luminosity evolution in addition to the density evolution, corresponding to an evolutionary rate of about (1+z) exp gamma, with gamma = 0.5-2.5, but a redshift of about 0.4. Assuming a steeper faint end slope of alpha = -1.3 similar to that observed in the Virgo cluster, could explain the data with a luminosity evolution rate of gamma = 1-2, without need for any density evolution. Acceptable fits are found by comparing composite density and luminosity evolution models to faint IRAS 60 micron source counts, implying that the blue and far-IR evolutionary rates may be similar.

Lonsdale, Carol J.↗
NASA NTRS1993

The starburst-AGN connection - A sensitive VLBI survey of luminous IRAS galaxies

Results of an 18 cm VLBI survey of 31 luminous, radio-compact IR galaxies are presented. Over half the sample galaxies show high-brightness temperature emission, with T sub b greater than 10 exp 5 K and structure on scales of 5-150 mas. The limits for nondetected sources are similar, consistent with a picture in which most of these galaxies have compact cores at a level of a few percent of the total radio flux density. Characteristics of the extended radio structure, infrared properties, and optical excitation are not good indicators of the detectability of VLBI-scale emission. Structural information and energetic considerations rule out a single supernova interpretation of the compact emission in these galaxies, although we cannot exclude the possibility of several simultaneous extraordinarily luminous radio supernovae within the central few hundred cubic parsec. Our results instead favor the presence of an AGN obscured by starburst-related dust.

Lonsdale, Colin J.↗
NASA NTRS1992

The Starburst-AGN Connection: A Sensitive VLBI Survey of Luminous IRAS Galaxies

Results of an 18 cm VLBI survey of 31 luminous (L_(fir) greater than 10^(11.25)L dot circle),radio-compact (theta less than approximately 0."25) infrared galaxies are presented. Over half thesample galaxies show high-brightness temperature emission, with T_b greater than 10^5K andstructure on scales of 5 - 150 mas. The median VLBI core power for detected sources is log P_(core)= 22.0(WHz^(-1)0, and the ratio of core to total 1.6 GHz flux density less than S_(core)/S_(total)greater than = 0.12. The limits for non- detected sources are similar, consistent with a picture inwhich all the galaxies have compact cores at a level of a few percent of the total radio flux density. Characteristics of the extended radio structure, infrared properties and optical excitation are not goodindicators of the detectability of VLBI-scale emission. Structural information and energeticconsiderations rule out a single supernova interpretation of the compact emission in these galaxies,though we cannot exclude the possibility of several simultaneous extraordinarily luminous radiosupernovae within the central few hundred pc^3. Our results instead favor the presence of an AGNobscured by starburst-related dust.

Lonsdale, Carol J.↗
NASA NTRS1992

A VLBI search for AGN radio cores in starburst galaxies

Results are presented of Mk III 18-cm VLBI observations of a small sample of IR-bright galaxies: four starburst galaxies which have no evidence of an AGN from the optical spectrum, two Seyfert 2 galaxies, and one previously unclassified Markarian galaxies. In Mrk 297 the compact radio source lies in an obscure clump near the edge of the galaxy. This is either the first known case of a detached nucleus (presumably as a result of disruption during a merger) or a radio supernova of unprecedented luminosity. No VLBI-scale emission was detected in the nucleus of the starburst galaxy Mrk 201 or in Mrk 928a, although the Seyfert 2 nucleus Mrk 928b was detected. Mrk 620 was found to have a milliarcsecond core, but Mrk 520 was not detected. Optical spectroscopy was obtained for five galaxies, including Mrk 520. It is demonstrated that, in luminous starburst galaxies, an active nucleus can effectively be completely hidden from view in the optical by dust. The results also support a physical or causal connection between classical nuclear activity and the starburst phenomenon.

Lonsdale, Colin J.↗
NASA NTRS1990

Galaxy evolution and large-scale structure in the far-infrared. II - The IRAS faint source survey

The new IRAS Faint Source Survey data base is used to confirm the conclusion of Hacking et al. (1987) that the 60 micron source counts fainter than about 0.5 Jy lie in excess of predictions based on nonevolving model populations. The existence of an anisotropy between the northern and southern Galactic caps discovered by Rowan-Robinson et al. (1986) and Needham and Rowan-Robinson (1988) is confirmed, and it is found to extend below their sensitivity limit to about 0.3 Jy in 60 micron flux density. The count anisotropy at f(60) greater than 0.3 can be interpreted reasonably as due to the Local Supercluster; however, no one structure accounting for the fainter anisotropy can be easily identified in either optical or far-IR two-dimensional sky distributions. The far-IR galaxy sky distributions are considerably smoother than distributions from the published optical galaxy catalogs. It is likely that structure of the large size discussed here have been discriminated against in earlier studies due to insufficient volume sampling.

Lonsdale, Carol J.↗
NASA NTRS1989

IRAS observations of optically selected galaxies. I - The properties of the UGC redshift sample

The FIR properties of more than 2400 optically selected galaxies in the Uppsala General Catalog are examined. The galaxies were detected by IRAS at 60 and 100 microns and have measured redshifts. A simple radiative transfer model is presented to study the nature of dust-heating sources. It is shown that for many normal disk galaxies, dust heated by old disk stars competes with dust heated by UV photons from newly formed stars. It is found that the 60-micron/100-micron flux density ratio may be used as an indicator of the dominant dust-heating source. Scaling relations with galaxy size and mass are presented which make it possible to estimate the contributions of any cirrus-like component to the total FIR luminosity.

Bothun, Gregory D.↗
NASA NTRS1989

The Wasilewski sample of emission-line galaxies - Follow-up CCD imaging and spectroscopic and IRAS observations

The results of an extensive imaging and spectroscopic follow-up of the objective prism-selected emission line galaxy (ELG) sample of Wasilewski (1982) are presented. Fluxes at 12, 25, 60, and 100 microns were also obtained from the coadded IRAS survey data. ELGs found by objective prism surveys are found to be generally small and underluminous galaxies which usually have higher than average optical surface brightness. The Seyfert detection rate in objective prism surveys is roughly 10 percent and the ratio of the space densities of Seyfert 2 to Seyfert 1 galaxies is significantly larger than unity. Most of the galaxies selected by objective prism surveys are star-forming, late-type spirals which often show disturbed morphology. About 25 percent of the galaxies detected by the surveys are faint, high-excitation metal-poor compact H II regions.

Bothun, Gregory D.↗
NASA NTRS1989

Galaxy evolution and large-scale structure in the far-infrared. I - IRAS pointed observations

Redshifts for 66 galaxies were obtained from a sample of 93 60-micron sources detected serendipitously in 22 IRAS deep pointed observations, covering a total area of 18.4 sq deg. The flux density limit of this survey is 150 mJy, 4 times fainter than the IRAS Point Source Catalog (PSC). The luminosity function is similar in shape with those previously published for samples selected from the PSC, with a median redshift of 0.048 for the fainter sample, but shifted to higher space densities. There is evidence that some of the excess number counts in the deeper sample can be explained in terms of a large-scale density enhancement beyond the Pavo-Indus supercluster. In addition, the faintest counts in the new sample confirm the result of Hacking et al. (1989) that faint IRAS 60-micron source counts lie significantly in excess of an extrapolation of the PSC counts assuming no luminosity or density evolution.

Lonsdale, Carol J.↗
NASA NTRS1988

Emission-line galaxies in the Slice of the Universe

The relative spatial distributions of emission-line galaxies (ELGs) and normal galaxies that lie in the sky area covered by the 'Slice' survey (de Lapparent et al., 1986) are considered. ELGs follow the same spatial distribution as found for the Slice galaxies, with the exception that they avoid the Coma cluster. It is pointed out that although the present ELGs are not shown to occur in regions of very low density, the luminosity distribution of the sample is such that luminosity/mass-dependent effects on the spatial distribution would not be noticeable.

Salzer, John J.↗
NASA NTRS1986

Bolometric luminosity evolution

The observations made by IRAS are capable of detecting evolution in the OB star formation rates of galaxies at cosmologically interesting redshifts if that evolution takes the form of star formation rates ten or more times higher than seen in nearby galaxies. Spectroscopic follow-up observations of IRAS-selected galaxies, and IRAS source counts, indicate that there may indeed exist a rare population of galaxies with such high star formation rates. The most luminous found so far approach quasars in luminosity.

Lonsdale, Carol J.↗