Nicholas morgan - Academia.edu (original) (raw)
Papers by Nicholas morgan
The Astrophysical Journal, 2001
We present results from X-ray observations of the quadruply lensed quasar RX J0911.4+0551 using d... more We present results from X-ray observations of the quadruply lensed quasar RX J0911.4+0551 using data obtained with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-ray Observatory. The 29 ks observation detects a total of ∼ 404 X-ray photons (0.3 to 7.0 keV) from the four images of the lensed quasar. Deconvolution of the aspect corrected data resolves all four lensed images, with relative positions in good agreement with optical measurements. When compared to contemporaneous optical data, one of the lensed images (component A3) is dimmer by a factor of ∼6 in X-rays with respect to the 2 brighter images (components A1 and A2). Spectral fitting for the combined images shows significant intrinsic absorption in the soft (0.2 to 2.4 keV) energy band, consistent with the mini-BAL nature of this quasar, while a comparison with ROSAT PSPC observations from 1990 shows a drop of ∼6.5 in the total soft bandpass flux. The observations also detect ∼ 157 X-ray photons arising from extended emission of the nearby cluster (peaked ∼ 42 ′′ SW of RX J0911.4+0551) responsible for the large external shear present in the system. The Chandra observation reveals the cluster emission to be complex and non-spherical, and yields a cluster temperature of kT = 2.3 +1.8 −0.8 keV and a 2.0 to 10 keV cluster luminosity within a 1 Mpc radius of L X = 7.6 +0.6 −0.2 × 10 43 ergs s −1 (error bars denote 90% confidence limits). Our mass estimate of the cluster within its virial radius is
The Astrophysical Journal, 2007
ABSTRACT
The Astrophysical Journal, 2006
We analyze V, I and H band HST images and two seasons of R-band monitoring data for the gravitati... more We analyze V, I and H band HST images and two seasons of R-band monitoring data for the gravitationally lensed quasar SDSS0924+0219. We clearly see that image D is a point-source image of the quasar at the center of its host galaxy. We can easily track the host galaxy of the quasar close to image D because microlensing has provided a natural coronograph that suppresses the flux of the quasar image by roughly an order of magnitude. We observe low amplitude, uncorrelated variability between the four quasar images due to microlensing, but no correlated variations that could be used to measure a time delay. Monte Carlo models of the microlensing variability provide estimates of the mean stellar mass in the lens galaxy (0.03 h 2 M ⊙ M 2.0 h 2 M ⊙), the accretion disk size (the disk temperature is 5 × 10 4 K at 1.3 × 10 14 h −1 cm r s 4.7 × 10 14 h −1 cm), and the black hole mass (6.6 × 10 6 M ⊙ M BH 4.4 × 10 7 M ⊙), all at 68% confidence. The black hole mass estimate based on microlensing is mildly inconsistent with an estimate of M BH = (1.5 ± 0.5) × 10 8 M ⊙ from the Mg II emission line width. If we extrapolate the best-fitting light curve models into the future, we expect images A and B to fade and images C and D to brighten. In particular, we estimate that image D has a roughly 16% probability of brightening by a factor of two during the next year and a 40% probability of brightening by an order of magnitude over the next decade.
The Astrophysical Journal, 2010
We use the microlensing variability observed for eleven gravitationally lensed quasars to show th... more We use the microlensing variability observed for eleven gravitationally lensed quasars to show that the accretion disk size at a rest-frame wavelength of 2500Å is related to the black hole mass by log(R 2500 /cm) = (15.78±0.12)+(0.80±0.17) log(M BH /10 9 M ⊙). This scaling is consistent with the expectation from thin disk theory (R ∝ M 2/3 BH), but when interpreted in terms of the standard thin disk model (T ∝ R −3/4), it implies that black holes radiate with very low efficiency, log(η) = −1.77 ± 0.29 + log(L/L E) where η = L/(Ṁ c 2). Only by making the maximum reasonable shifts in the average inclination, Eddington factors and black hole masses can we raise the efficiency estimate to be marginally consistent with typical efficiency estimates (η ≈ 10%). With one exception, these sizes are larger by a factor of ∼ 4 than the size needed to produce the observed 0.8 µm quasar flux by thermal radiation from a thin disk with the same T ∝ R −3/4 temperature profile. While scattering a significant fraction of the disk emission on large scales or including a large fraction of contaminating line emission can reduce the size discrepancy, resolving it also appears to require that accretion disks have flatter temperature/surface brightness profiles.
The Astronomical Journal, 1999
We report the discovery and ground based observations of the new gravitational lens CTQ 414. The ... more We report the discovery and ground based observations of the new gravitational lens CTQ 414. The source quasar lies at a redshift of z = 1.29 with a B magnitude of 17.6. Ground based optical imaging reveals two point sources separated by 1. 2 with a magnitude difference of roughly 1 mag. Subtraction of two stellar point spread functions from images obtained in subarcsecond seeing consistently leaves behind a faint, residual object. Fits for two point sources plus an extended object places the fainter object collinear with the two brighter components. Subsequent HST/NICMOS observations have confirmed the identification of the fainter object as the lensing galaxy. VLA observations at 8.46 GHz reveal that all components of the lensing system are radio quiet down to the 0.2 mJy flux level.
The Astronomical Journal, 2001
We present our ground-based optical imaging, spectral analysis, and high resolution radio mapping... more We present our ground-based optical imaging, spectral analysis, and high resolution radio mapping of the gravitational lens candidate FBQ 1633+3134. This z = 1.52, B = 17.6 quasar appears double on CCD images with an image separation of 0. 66 and a flux ratio of ∼ 3 : 1 across BV RI filters. A single 0.27 mJy radio source is detected at 8.46 GHz, coincident to within an arcsecond of both optical components, but no companion at radio wavelengths is detected down to a flux level of 0.1 mJy (3σ). Spectral observations reveal a rich metal-line absorption system consisting of a strong Mg II doublet and associated Fe I and Fe II absorption features, all at an intervening redshift of z = 0.684, suggestive of a lensing galaxy. Point spread function subtraction however shows no obvious signs of a third object between the two quasar images, and places a detection limit of I ∼ > 23.0 if such an object exists. Although the possibility that FBQ 1633+3134 is a binary quasar cannot be ruled out, the evidence is consistent with it being a single quasar lensed by a faint, metal-rich galaxy.
The Astronomical Journal, 2002
Human Reproduction, 2008
BACKGROUND: Preterm birth (PTB) is hypothesized to be an inflammatory response disease. However, ... more BACKGROUND: Preterm birth (PTB) is hypothesized to be an inflammatory response disease. However, no single factor alone is likely to explain PTB risk. It is more probable that coordinated networks of cytokines affect risk. METHODS: Therefore, we examined the relationships between amniotic fluid (AF) cytokines/chemokines and related biomarkers in PTB and normal term deliveries in African Americans and Caucasians. Data were obtained from African American (41 preterm labor and 91 term labor) and Caucasian (105 preterm labor and 100 term labor) pregnant mothers. Pro-inflammatory cytokines and related molecules interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor-(TNF)-a, TNF soluble receptors (sTNFR1 and sTNFR2), and anti-inflammatory cytokine IL-10 that were all previously associated with PTB were studied. Correlations between biomarkers were calculated; differences of correlation coefficients between AF from African American and Caucasian samples in preterm labor and term labor were measured. RESULTS: Multiple differences were observed between African American and Caucasian preterm and term birth groups. In term birth the strongest differences were between pro-and anti-inflammatory correlations, whereas in PTB differences were equally distributed between pro-inflammatory/anti-inflammatory and pro-inflammatory/pro-inflammatory correlations. Three correlation patterns differed significantly between AF from PTB African Americans with and without microbial invasion of the intra-amniotic cavity (MIAC); no differences were observed in Caucasians with MIAC. CONCLUSION: Correlation analyses of cytokine measurements suggest coordinated interplay during pregnancy; significant differences exist between African Americans and Caucasians. Such analyses can serve as a means of understanding risk factors in these populations.
Bioorganic & Medicinal …, 1994
We report the discovery and ground based observations of the new gravitational lens CTQ 414. The ... more We report the discovery and ground based observations of the new gravitational lens CTQ 414. The source quasar lies at a redshift of z = 1.29 with a B magnitude of 17.6. Ground based optical imaging reveals two point sources separated by 1. 2 with a magnitude difference of roughly 1 mag. Subtraction of two stellar point spread functions from images obtained in subarcsecond seeing consistently leaves behind a faint, residual object. Fits for two point sources plus an extended object places the fainter object collinear with the two brighter components. Subsequent HST/NICMOS observations have confirmed the identification of the fainter object as the lensing galaxy. VLA observations at 8.46 GHz reveal that all components of the lensing system are radio quiet down to the 0.2 mJy flux level.
American Journal of Obstetrics and Gynecology, 2008
Preterm birth rate in the United States is higher in blacks than whites. It has been hypothesized... more Preterm birth rate in the United States is higher in blacks than whites. It has been hypothesized that a differential inflammatory response may explain this disparity. The objective of this study is to examine the inflammatory cytokine, tumor necrosis factor (TNF)-alpha and soluble TNF receptor concentrations (sTNFR1 and sTNFR2) in the amniotic fluid of black and white women at delivery. Amniotic fluid samples were collected during active labor from 158 cases (preterm births, gestational age 22(0/7) weeks to 36(0/7) weeks, 52 black and 106 white) and 175 controls (term births, gestational age 37(0/7) weeks to 42(0/7) weeks, 87 black and 88 white) at Centennial Women's Hospital, Nashville, TN. Amniotic fluid TNF-alpha, sTNFR1, and sTNFR2 concentrations and the molar ratios of TNF-alpha to its receptors were compared between cases and controls within each racial group. Median TNF-alpha concentration was associated with preterm birth when whites and blacks were analyzed together, with cases having higher values (191.5 pg/mL) than controls (68.9 pg/mL; P < .001). There were no significant associations with sTNFR1 or sTNFR2 concentrations between cases (2409.4 and 2934.3 pg/mL, respectively) and controls (2759.9 and 3084.1 pg/mL, respectively) when the racial groups were analyzed together (P = .08, P = .4, respectively). Black cases associated with higher TNF-alpha concentrations (1287.0 pg/mL in cases and 67.3 pg/mL in controls; P…
Astronomy and Astrophysics, Mar 1, 2009
Aims. We report on the redshift of the lensing galaxy and of the quasar QJ 0158-4325 and on the l... more Aims. We report on the redshift of the lensing galaxy and of the quasar QJ 0158-4325 and on the lens model of the system. Methods. A deep VLT/FORS2 spectrum and HST/NICMOS-F160W images are deconvolved. From the images we derive the light profile of the lensing galaxy and an accurate relative astrometry for the system. In addition we measure the flux ratio between the quasar images in the Mg II emission line to constrain the mass model. Results. From the spectrum we measure the redshift of the lensing galaxy (z= 0.317$\ pm ...
Arxiv preprint astro-ph …, 2004
G.Aldering1, W. Althouse2, R. Amanullah3, J. Annis4, P. Astier5, C. Baltay6, E. Barrelet5, S. Bas... more G.Aldering1, W. Althouse2, R. Amanullah3, J. Annis4, P. Astier5, C. Baltay6, E. Barrelet5, S. Basa7, C. Bebek1, L. Bergström3, G. Bernstein8, M. Bester9, B. Bigelow10, R. Blandford2, R. Bohlin11, A. Bonissent12, C. Bower13, M. Brown10, M. Campbell10, W. Carithers1, E. ...
The Astrophysical Journal, 2001
We present results from X-ray observations of the quadruply lensed quasar RX J0911.4+0551 using d... more We present results from X-ray observations of the quadruply lensed quasar RX J0911.4+0551 using data obtained with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-ray Observatory. The 29 ks observation detects a total of ∼ 404 X-ray photons (0.3 to 7.0 keV) from the four images of the lensed quasar. Deconvolution of the aspect corrected data resolves all four lensed images, with relative positions in good agreement with optical measurements. When compared to contemporaneous optical data, one of the lensed images (component A3) is dimmer by a factor of ∼6 in X-rays with respect to the 2 brighter images (components A1 and A2). Spectral fitting for the combined images shows significant intrinsic absorption in the soft (0.2 to 2.4 keV) energy band, consistent with the mini-BAL nature of this quasar, while a comparison with ROSAT PSPC observations from 1990 shows a drop of ∼6.5 in the total soft bandpass flux. The observations also detect ∼ 157 X-ray photons arising from extended emission of the nearby cluster (peaked ∼ 42 ′′ SW of RX J0911.4+0551) responsible for the large external shear present in the system. The Chandra observation reveals the cluster emission to be complex and non-spherical, and yields a cluster temperature of kT = 2.3 +1.8 −0.8 keV and a 2.0 to 10 keV cluster luminosity within a 1 Mpc radius of L X = 7.6 +0.6 −0.2 × 10 43 ergs s −1 (error bars denote 90% confidence limits). Our mass estimate of the cluster within its virial radius is
The Astrophysical Journal, 2007
ABSTRACT
The Astrophysical Journal, 2006
We analyze V, I and H band HST images and two seasons of R-band monitoring data for the gravitati... more We analyze V, I and H band HST images and two seasons of R-band monitoring data for the gravitationally lensed quasar SDSS0924+0219. We clearly see that image D is a point-source image of the quasar at the center of its host galaxy. We can easily track the host galaxy of the quasar close to image D because microlensing has provided a natural coronograph that suppresses the flux of the quasar image by roughly an order of magnitude. We observe low amplitude, uncorrelated variability between the four quasar images due to microlensing, but no correlated variations that could be used to measure a time delay. Monte Carlo models of the microlensing variability provide estimates of the mean stellar mass in the lens galaxy (0.03 h 2 M ⊙ M 2.0 h 2 M ⊙), the accretion disk size (the disk temperature is 5 × 10 4 K at 1.3 × 10 14 h −1 cm r s 4.7 × 10 14 h −1 cm), and the black hole mass (6.6 × 10 6 M ⊙ M BH 4.4 × 10 7 M ⊙), all at 68% confidence. The black hole mass estimate based on microlensing is mildly inconsistent with an estimate of M BH = (1.5 ± 0.5) × 10 8 M ⊙ from the Mg II emission line width. If we extrapolate the best-fitting light curve models into the future, we expect images A and B to fade and images C and D to brighten. In particular, we estimate that image D has a roughly 16% probability of brightening by a factor of two during the next year and a 40% probability of brightening by an order of magnitude over the next decade.
The Astrophysical Journal, 2010
We use the microlensing variability observed for eleven gravitationally lensed quasars to show th... more We use the microlensing variability observed for eleven gravitationally lensed quasars to show that the accretion disk size at a rest-frame wavelength of 2500Å is related to the black hole mass by log(R 2500 /cm) = (15.78±0.12)+(0.80±0.17) log(M BH /10 9 M ⊙). This scaling is consistent with the expectation from thin disk theory (R ∝ M 2/3 BH), but when interpreted in terms of the standard thin disk model (T ∝ R −3/4), it implies that black holes radiate with very low efficiency, log(η) = −1.77 ± 0.29 + log(L/L E) where η = L/(Ṁ c 2). Only by making the maximum reasonable shifts in the average inclination, Eddington factors and black hole masses can we raise the efficiency estimate to be marginally consistent with typical efficiency estimates (η ≈ 10%). With one exception, these sizes are larger by a factor of ∼ 4 than the size needed to produce the observed 0.8 µm quasar flux by thermal radiation from a thin disk with the same T ∝ R −3/4 temperature profile. While scattering a significant fraction of the disk emission on large scales or including a large fraction of contaminating line emission can reduce the size discrepancy, resolving it also appears to require that accretion disks have flatter temperature/surface brightness profiles.
The Astronomical Journal, 1999
We report the discovery and ground based observations of the new gravitational lens CTQ 414. The ... more We report the discovery and ground based observations of the new gravitational lens CTQ 414. The source quasar lies at a redshift of z = 1.29 with a B magnitude of 17.6. Ground based optical imaging reveals two point sources separated by 1. 2 with a magnitude difference of roughly 1 mag. Subtraction of two stellar point spread functions from images obtained in subarcsecond seeing consistently leaves behind a faint, residual object. Fits for two point sources plus an extended object places the fainter object collinear with the two brighter components. Subsequent HST/NICMOS observations have confirmed the identification of the fainter object as the lensing galaxy. VLA observations at 8.46 GHz reveal that all components of the lensing system are radio quiet down to the 0.2 mJy flux level.
The Astronomical Journal, 2001
We present our ground-based optical imaging, spectral analysis, and high resolution radio mapping... more We present our ground-based optical imaging, spectral analysis, and high resolution radio mapping of the gravitational lens candidate FBQ 1633+3134. This z = 1.52, B = 17.6 quasar appears double on CCD images with an image separation of 0. 66 and a flux ratio of ∼ 3 : 1 across BV RI filters. A single 0.27 mJy radio source is detected at 8.46 GHz, coincident to within an arcsecond of both optical components, but no companion at radio wavelengths is detected down to a flux level of 0.1 mJy (3σ). Spectral observations reveal a rich metal-line absorption system consisting of a strong Mg II doublet and associated Fe I and Fe II absorption features, all at an intervening redshift of z = 0.684, suggestive of a lensing galaxy. Point spread function subtraction however shows no obvious signs of a third object between the two quasar images, and places a detection limit of I ∼ > 23.0 if such an object exists. Although the possibility that FBQ 1633+3134 is a binary quasar cannot be ruled out, the evidence is consistent with it being a single quasar lensed by a faint, metal-rich galaxy.
The Astronomical Journal, 2002
Human Reproduction, 2008
BACKGROUND: Preterm birth (PTB) is hypothesized to be an inflammatory response disease. However, ... more BACKGROUND: Preterm birth (PTB) is hypothesized to be an inflammatory response disease. However, no single factor alone is likely to explain PTB risk. It is more probable that coordinated networks of cytokines affect risk. METHODS: Therefore, we examined the relationships between amniotic fluid (AF) cytokines/chemokines and related biomarkers in PTB and normal term deliveries in African Americans and Caucasians. Data were obtained from African American (41 preterm labor and 91 term labor) and Caucasian (105 preterm labor and 100 term labor) pregnant mothers. Pro-inflammatory cytokines and related molecules interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor-(TNF)-a, TNF soluble receptors (sTNFR1 and sTNFR2), and anti-inflammatory cytokine IL-10 that were all previously associated with PTB were studied. Correlations between biomarkers were calculated; differences of correlation coefficients between AF from African American and Caucasian samples in preterm labor and term labor were measured. RESULTS: Multiple differences were observed between African American and Caucasian preterm and term birth groups. In term birth the strongest differences were between pro-and anti-inflammatory correlations, whereas in PTB differences were equally distributed between pro-inflammatory/anti-inflammatory and pro-inflammatory/pro-inflammatory correlations. Three correlation patterns differed significantly between AF from PTB African Americans with and without microbial invasion of the intra-amniotic cavity (MIAC); no differences were observed in Caucasians with MIAC. CONCLUSION: Correlation analyses of cytokine measurements suggest coordinated interplay during pregnancy; significant differences exist between African Americans and Caucasians. Such analyses can serve as a means of understanding risk factors in these populations.
Bioorganic & Medicinal …, 1994
We report the discovery and ground based observations of the new gravitational lens CTQ 414. The ... more We report the discovery and ground based observations of the new gravitational lens CTQ 414. The source quasar lies at a redshift of z = 1.29 with a B magnitude of 17.6. Ground based optical imaging reveals two point sources separated by 1. 2 with a magnitude difference of roughly 1 mag. Subtraction of two stellar point spread functions from images obtained in subarcsecond seeing consistently leaves behind a faint, residual object. Fits for two point sources plus an extended object places the fainter object collinear with the two brighter components. Subsequent HST/NICMOS observations have confirmed the identification of the fainter object as the lensing galaxy. VLA observations at 8.46 GHz reveal that all components of the lensing system are radio quiet down to the 0.2 mJy flux level.
American Journal of Obstetrics and Gynecology, 2008
Preterm birth rate in the United States is higher in blacks than whites. It has been hypothesized... more Preterm birth rate in the United States is higher in blacks than whites. It has been hypothesized that a differential inflammatory response may explain this disparity. The objective of this study is to examine the inflammatory cytokine, tumor necrosis factor (TNF)-alpha and soluble TNF receptor concentrations (sTNFR1 and sTNFR2) in the amniotic fluid of black and white women at delivery. Amniotic fluid samples were collected during active labor from 158 cases (preterm births, gestational age 22(0/7) weeks to 36(0/7) weeks, 52 black and 106 white) and 175 controls (term births, gestational age 37(0/7) weeks to 42(0/7) weeks, 87 black and 88 white) at Centennial Women's Hospital, Nashville, TN. Amniotic fluid TNF-alpha, sTNFR1, and sTNFR2 concentrations and the molar ratios of TNF-alpha to its receptors were compared between cases and controls within each racial group. Median TNF-alpha concentration was associated with preterm birth when whites and blacks were analyzed together, with cases having higher values (191.5 pg/mL) than controls (68.9 pg/mL; P < .001). There were no significant associations with sTNFR1 or sTNFR2 concentrations between cases (2409.4 and 2934.3 pg/mL, respectively) and controls (2759.9 and 3084.1 pg/mL, respectively) when the racial groups were analyzed together (P = .08, P = .4, respectively). Black cases associated with higher TNF-alpha concentrations (1287.0 pg/mL in cases and 67.3 pg/mL in controls; P…
Astronomy and Astrophysics, Mar 1, 2009
Aims. We report on the redshift of the lensing galaxy and of the quasar QJ 0158-4325 and on the l... more Aims. We report on the redshift of the lensing galaxy and of the quasar QJ 0158-4325 and on the lens model of the system. Methods. A deep VLT/FORS2 spectrum and HST/NICMOS-F160W images are deconvolved. From the images we derive the light profile of the lensing galaxy and an accurate relative astrometry for the system. In addition we measure the flux ratio between the quasar images in the Mg II emission line to constrain the mass model. Results. From the spectrum we measure the redshift of the lensing galaxy (z= 0.317$\ pm ...
Arxiv preprint astro-ph …, 2004
G.Aldering1, W. Althouse2, R. Amanullah3, J. Annis4, P. Astier5, C. Baltay6, E. Barrelet5, S. Bas... more G.Aldering1, W. Althouse2, R. Amanullah3, J. Annis4, P. Astier5, C. Baltay6, E. Barrelet5, S. Basa7, C. Bebek1, L. Bergström3, G. Bernstein8, M. Bester9, B. Bigelow10, R. Blandford2, R. Bohlin11, A. Bonissent12, C. Bower13, M. Brown10, M. Campbell10, W. Carithers1, E. ...