arXiv subjects

D. Crampton

Publications and source records attributed to D. Crampton.

At least 37 records · Page 2Linked to original sources

arXiv2001

The Canada-France deep fields survey-I: 100,000 galaxies, 1 deg^2: a precise measurement of ω(θ) to IAB~25

(abridged) Using the UH8K mosaic camera, we have measured the angular correlation function ω(θ) for 100,000 galaxies over four widely separated fields totalling ~1°^2 and reaching IAB~25.5. With this sample we investigate the dependence of ω(θ) at 1', A_ω(1'), on sample median IAB magnitude in the range 19.5 1. Models with ε~0 cannot simultaneously match both bright and faint measurements of A_ω(1`). We show how this result is a natural consequence of the ``bias-free'' nature of the εformalism and is consistent with the field galaxy population in the range 22.0<IAB<24.0 being dominated by galaxies of low intrinsic luminosity.

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arXiv2001

Far-UV Observations of the Galactic Supersoft Binary RXJ0019.8+2156 (QR And)

FUSE spectra were obtained of the supersoft X-ray binary RX J0019.8+2156 (QR And) during 16 consecutive spacecraft orbits, covering the binary orbit (P=15.85 hr) with about 0.2 phase overlap. The spectrum is dominated by strong H2 absorption (column density ~10**20 g/cm**2), which appears at a radial velocity different from other interstellar absorption lines and may be partially circumbinary. This absorption makes study of spectral features from the binary system difficult. The only well-detected emission lines are He II, 1085A, and O VI, 1032A, (the other line of the O VI doublet, 1037A, is largely obscured by strong H2 absorption). The O VI shows a P Cygni profile that varies in velocity and strength with binary phase. We compare this with similar changes seen in Balmer line profiles. We extract the FUV light curve and compare it with the optical light curve. There is an eclipse in both wavelength regions, but the FUV minimum lasts much longer, well beyond the visible light egress. The FUV results are discussed in connection with the binary model and mass flows within the system.

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arXiv2000

Emission line imaging of QSOs with high resolution

We report the first detection of emission line gas within the host galaxies of high redshift QSOs. This was done using narrow-band imaging at the redshifted wavelengths of [O III] and H alpha, using the PUEO adaptive optics camera of the CFHT. The QSOs are all radio-quiet or very compact radio sources. In all five observed QSOs, which have redshifts 0.9 to 2.4, we find extended line emission that lies within 0.5" (a few Kpc) of the nucleus. The emission (redshifted) equivalent widths range from 35 to 300A. Where there is radio structure, the line emission is aligned with it. We also report on continuum fluxes and possible companions. Two of the QSOs are very red, and have high resolved continuum flux.

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arXiv1999

Hubble Space Telescope imaging of the CFRS and LDSS redshift surveys - IV. Influence of mergers in the evolution of faint field galaxies from z~1

HST images of a sample of 285 galaxies with measured z from the CFRS and Autofib-LDSS redshift surveys are analysed to derive the evolution of the merger fraction out to z~1. We have performed visual and machine-based merger identifications, as well as counts of bright pairs of galaxies with magnitude differences less than 1.5 mag. We find that the pair fraction increases with z, with up to ~20% of the galaxies being in physical pairs at z~0.75-1. We derive a merger fraction varying with z as (1+z)^{3.2 +/- 0.6}, after correction for line-of-sight contamination, in excellent agreement with the merger fraction derived from the visual classification of mergers for which m = 3.4 +/- 0.6. After correcting for seeing effects on the ground-based selection of survey galaxies, we conclude that the pair fraction evolves as (1+z)^{2.7 +/- 0.6}. This implies that an average L* galaxy will have undergone 0.8 to 1.8 merger events from z=1 to 0, with 0.5 to 1.2 merger events occuring in a 2 Gyr time span at z~0.9. This result is consistent with predictions from semi-analytical models of galaxy formation. From the simple co-addition of the observed luminosities of the galaxies in pairs, physical mergers are computed to lead to a brightening of 0.5 mag for each pair on average, and a boost in star formation rate of a factor of 2, as derived from the average [O II] equivalent widths. Mergers of galaxies are therefore contributing significantly to the evolution of both the luminosity function and luminosity density of the Universe out to z~1.

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arXiv1999

Hubble Space Telescope Imaging of the CFRS and LDSS Redshift Surveys---III. Field elliptical galaxies at 0.2 < z < 1.0

Surface photometry has been performed on a sample of 46 field elliptical galaxies. These galaxies are described well by a deVaucouleurs R^{1/4} profile. The sample was selected from the combined Canada-France and LDSS redshift surveys and spans the range 0.20 < z < 1.00. The relationship between galaxy half-light radius and luminosity evolves such that a galaxy of a given size is more luminous by Delta M_B=-0.97 \pm 0.14 mag at z=0.92 and the mean rest-frame color shifts blueward by Delta (U-V) =-0.68 \pm 0.11 at z=0.92 relative to the local cluster relations. Approximately 1/3 of these elliptical galaxies exhibit [OII] 3727 emission lines with equivalent widths > 15 angstroms indicating ongoing star formation. Estimated star-formation rates imply that \le 5% of the stellar mass in the elliptical galaxy population has been formed since z=1. We see no evidence for a decline in the space density of early-type galaxies with look-back time. The statistics and a comparison with local luminosity functions are both consistent with the view that the population of massive early-type galaxies was largely in place by z~1. This implies that merging is not required since that time to produce the present-day space density of elliptical galaxies.

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arXiv1998

QSO hosts and environments at z=0.9 to 4.2: JHK images with adaptive optics

We have observed nine QSOs with redshifts 0.85 to 4.16 at near-IR wavelengths with the adaptive optics bonnette of the Canada-France-Hawaii telescope. Exposure times ranged from 1500 to 24000s (mostly near 7000s) in J, H, or K bands, with pixels 0.035 arcsec on the sky. The FWHM of the co-added images at the location of the quasars are typically 0.16 arcsec. Including another QSO published previously, we find associated QSO structure in at least eight of ten objects, including the QSO at z = 4.16. The structures seen in all cases include long faint features which appear to be tidal tails. In four cases we have also resolved the QSO host galaxy, but find them to be smooth and symmetrical: future PSF removal may expand this result. Including one object previously reported, of the nine objects with more extended structure, five are radio-loud, and all but one of these appear to be in a dense small group of compact galaxy companions. The radio-quiet objects do not occupy the same dense environments, as seen in the NIR. In this small sample we do not find any apparent trends of these properties with redshift, over the range 0.8 < z < 2.4. The colors of the host galaxies and companions are consistent with young stellar populations at the QSO redshift. Our observations suggest that adaptive optic observations in the visible region will exhibit luminous signatures of the substantial star-formation activity that must be occurring.

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arXiv1998

Deep Galaxy survey at 6.75 micron with the ISO satellite

Deep 6.75um mid-IR ISOCAM observations were obtained of the Canada-France Redshift Survey (CFRS) 1415+52 field with the Infrared Space Observatory. The identification of the sources with optical counterparts is described in detail, and a classification scheme is devised which depends on the S/N of the detection and the inverse probability of chance coincidence. 83% of the 54 ISOCAM sources are identified with Iab<23.5 counterparts. The (I-K)ab colors, radio properties, spectrophotometric properties and frequency of nuclear activity of these counterparts differ on average from those of typical CFRS galaxies. CFRS spectra are available for 21 of the sources which have Iab <= 22.5 (including 7 stars). Most of the strongest sources are stars or AGN. Among the non--stellar counterparts with spectra, 40% are AGNs, and 53% are galaxies that display star formation activity and/or significant contributions of A stars. The ISOCAM sources also display an IR excess, even when compared with heavily-reddened local starburst galaxies. An upper limit of 30% of extragalactic ISO sources could be at z>1 of the 44 S6.75um > 150uJy sources which are non-stellar (7 "spectroscopic" and 3 "photometric" stars excluded)

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arXiv1998

15um ISO observations of a CFRS field: the cosmic SFR as derived from UV, optical, mid-IR and radio photometry

The CFRS 1452+52 field has been deeply imaged with the Infrared Space Observatory (ISO) using ISOCAM through the LW3 filter (12-18um). Careful data analysis and comparison to deep optical and radio data have allowed us to generate a catalog of 78 15um sources with both radio and optical identifications. They are redder and lie at higher redshift than I-band selected galaxies, with most of them being star-forming galaxies. We have considered the galaxies detected at radio and 15$μ$m wavelengths which potentially include all strong and heavily extincted starbursts, up to z=1. Spectral energy distributions (SED) for each of the sources have been derived using deep radio, mid-IR, near-IR, optical and UV photometry. The sources were then spectrally classified by comparing to SEDs of well known nearby galaxies. By deriving their FIR luminosities by interpolation, we can estimate their Star Formation Rate (SFR) in a way which does not depend sensitively on the extinction. 75% (-40%, +10%) of the star formation at $z \le 1$ is related to IR emission and the global extinction is in the range Av=0.5 -- 0.85. While heavily extincted starbursts, with SFR in excess of 100 Mo/yr constitute less than a percent of all galaxies, they contribute about 18% of the SFR density out to z=1. Their morphologies range from S0 to Sab, and more than a third are interacting systems. The SFR derived by FIR fluxes is likely to be ~2.9 times higher than those previously estimated from UV fluxes. The derived stellar mass formed since the redshift of 1 could be too high when compared to the present day stellar mass density. This might be due to an IMF in distant star-forming galaxies different from the solar neighborhood one, or to an underestimate of the local stellar mass density.

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arXiv1998

Near-IR Images of the Torus and Micro-Spiral Structure in NGC 1068 using Adaptive Optics

We present diffraction-limited near-IR images in J, H and K of the nucleus of NGC 1068, obtained with the Adaptive Optics system {Pueo} at CFHT. The achieved resolution (0.12") reveals several components, particularly prominent on the [J-K] image: a) an unresolved, conspicuous core (size < 9 pc); b) an elongated structure at P.A. ~102 deg, beginning to show up at radius ~ 15 pc; c) a S-shaped structure with radial extent ~ 20 pc, including a bar-like central elongation at P.A. ~ 15 deg and two short spiral arms. The K core is at the location of the putative central engine (radio source S1) : the core is likely the emission from the hot inner walls of the dust/molecular torus. The extremely red colors of the central 0.2", [J-K]=7.0, [H-K]=3.8, lead to an extinction Av > 25. The elongated structure at P.A.~ 102 deg may trace the presence of cooler dust within and around the torus. This interpretation is supported by two facts : a) the elongated structure is perpendicular to the local radio jet originating at S1; b) its direction follows exactly that of the disk of ionized gas recently found with the VLBA. The S-shaped feature suggests an extremely compact barred spiral structure, that would be the innermost of a series of nested spiral structures, as predicted by simulations. This is supported by the inner stellar distribution - deduced from the J image - which clearly follows an exponential disk with a 19 pc scale-length, precisely that expected from the rotation of a bar.

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arXiv1998

The eclipsing supersoft X-ray binary CAL 87

We present and discuss 25 spectra obtained in November 1996, covering all phases of the CAL 87 binary system. These spectra are superior both in signal-to-noise and wavelength coverage to previously published data so that additional spectral features can be measured. Photometry obtained on the same nights is used to confirm the ephemeris and to compare with light curves from previous years. Analysis of the color variation through the orbital cycle has been carried out using archival MACHO data. When a barely resolved red field star is accounted for, there is no (V-R)-color variation, even through eclipse. There have been substantial changes in the depth of minimum light since 1988; it has decreased more than 0.5 mag in the last several years. The spectral features and radial velocities are also found to vary not only through the 0.44-day orbit but also over timescales of a year or more. Possible interpretations of these long-term changes are discussed. The 1996 spectra contain phase-modulated Balmer absorption lines not previously seen, apparently arising in gas flowing from the region of the compact star. The changes in emission-line strengths with orbital phase indicate there are azimuthal variations in the accretion disk structures. Radial velocities of several lines give different amplitudes and phasing, making determination of the stellar masses difficult. All solutions for the stellar masses indicate that the companion star is considerably less massive than the degenerate star. The Balmer absorption-line velocities correspond to masses of ~1.4Msun for the degenerate star and ~0.4Msun for the mass donor. However, the strong He II emission lines indicate a much more massive accreting star, with Mx>4Msun.

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arXiv1998

Six supersoft X-ray binaries: system parameters and twin-jet outflows

A comparison is made between the properties of CAL 83, CAL 87, RX J0513.9-6951, 1E 0035.4-7230 (SMC 13), RX J0019.8+2156, and RX J0925.7-4758, all supersoft X-ray binaries. Spectra with the same resolution and wavelength coverage of these systems are compared and contrasted. Some new photometry is also presented. The equivalent widths of the principal emission lines of H and He II differ by more than an order of magnitude among these sources, although those of the highest ionization lines (e.g. O VI) are very similar. In individual systems, the velocity curves derived from various ions often differ in phasing and amplitude, but those whose phasing is consistent with the light curves (implying the lines are formed near the compact star) give masses of $\sim 1.2M_{\odot}$ and $\sim 0.5M_{\odot}$ for the degenerate and mass-losing stars, respectively. This finding is in conflict with currently prevailing theoretical models for supersoft binaries. The three highest luminosity sources show evidence of "jet" outflows, with velocities of $\sim 1-4 \times10^3 km/s$. In CAL 83 the shape of the He II 4686Åprofile continues to show evidence that these jets may precess with a period of $\sim 69$ days.

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arXiv1997

Performance of the CFHT Adaptive Optics Bonnette

Extensive results from the commissioning phase of PUEO, the adaptive optics instrument adaptor for the Canada-France-Hawaii telescope, are presented and discussed. Analyses of more than 750 images recorded with a CCD and a near-IR camera on 16 nights in wavelengths from B to H are used to derive the properties of the compensated wavefront and images in a variety of conditions. The performance characteristics of the system are analyzed and presented in several ways, in terms of delivered Strehl ratios, full-width-half-maxima, and quantities describing the improvements of both. A qualitative description is given of how the properties of the corrected images result from the structure function of the compensated phase. Under median seeing conditions, PUEO delivers essentially diffraction-limited images at H and K, images with FWHM ~0.1" at J and I, and provides significant gains down to B, with guide stars as faint as R = 14. During good conditions, substantial gains were realized with guide stars as faint as R = 17. A simple user-interface and software which automatically and continuously optimizes the mode gains during observations makes the operational efficiency extremely high. A few astronomical examples are briefly discussed.

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arXiv1997

HST imaging of CFRS and LDSS galaxies - I: Morphological Properties

(Abridged) We analyse Hubble Space Telescope images of a complete sample of 341 galaxies drawn from both the Canada France and Autofib/Low Dispersion Survey Spectrograph ground-based redshift surveys. We discuss morphological classifications of these galaxies, and quantify possible biases that may arise from various redshift-dependent effects. We then discuss these biases in the context of automated classifications, and quantify the expected misclassification in our system. After allowing for such biases, the redshift distribution for normal spirals, together with their luminosity function derived as a function of redshift, indicates approximately 1 magnitude of luminosity evolution in B(AB) by z=1. The elliptical sample is too small for precise evolutionary constraints. However, we find a substantial increase in the proportion of galaxies with irregular morphology at large redshift. These galaxies also appear to be the dominant cause of the rapid rise with redshift in the blue luminosity density identified in the redshift surveys. Although galaxies with irregular morphology may well comprise a mixture of different physical systems and might not correspond to present day irregulars, it is clear that the apparently declining abundance and luminosities of our distant ``irregulars'' holds an important key to understanding recent evolution in the star formation history of normal galaxies.

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arXiv1997

Hubble Space Telescope imaging of the CFRS and LDSS redshift surveys II: Structural parameter and the evolution of disk galaxies to z=1

(Abridged) Several aspects of the evolution of star-forming galaxies are studied using measures of the 2-dimensional surface brightness profile of a sample of 341 faint objects selected from the CFRS and LDSS redshift surveys that have been observed with the Hubble Space Telescope. The size function of disk scale lengths in disk-dominated galaxies is found to stay roughly constant to z=1. This result, which is strengthened by inclusion of the local de Jong et al (1996) size function, suggests that the scale lengths of typical disks can not have grown substantially with cosmic epoch since z=1, unless a corresponding number of large disks have been destroyed through merging. In addition to a roughly constant number density, the galaxies with large disks have, as a set, properties consistent with the idea that they are similar galaxies observed at different cosmic epochs. However, on average, they show higher B-band disk surface brightnesses, bluer overall (U-V) colors, higher [OII] 3727 equivalent widths and less regular morphologies at high redshift than at low redshift, suggesting an increase in the star-formation rate by a factor of about 3 to z=0.7. This is consistent with the expectations of recent models for the evolution of the disk of the Milky Way and similar galaxies. The evolution of the large disk galaxies is probably not sufficient to account for the evolution of the overall luminosity function of galaxies over the interval 0<z<1, especially if Omega=1. Analysis of the half-light radii of all the galaxies in the sample and construction of the bivariate size-luminosity function suggests that larger changes in the galaxy population are due to smaller galaxies, those with half-light radii around 5 h_{50}^{-1} kpc

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arXiv1997

The Stellar Content Near the Galactic Center

High angular resolution J, H, K, and L' images are used to investigate the stellar content within 6 arcsec of SgrA*. The data, which are complete to K ~ 16, are the deepest multicolor observations of the region published to date.

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arXiv1996

Wide-field CCD imaging at CFHT: the MOCAM example

We describe a new 4096x4096 pixel CCD mosaic camera (MOCAM) available at the prime focus of the Canada-France-Hawaii Telescope (CFHT). The camera is a mosaic of four 2048x2048$ Loral frontside-illuminated CCDs with 15 $μ$m pixels, providing a field of view of 14'x14' at a scale of 0.21''/pixel. MOCAM is equipped with B, V, R and I filters and has demonstrated image quality of 0.5''-0.6'' FWHM over the entire field. MOCAM will also be used with the CFHT adaptive optic bonnette and will provide a field of view of 90'' at a scale of 0.02 ''/pixel. MOCAM works within the CFHT Pegasus software environment and observers familiar with this system require no additional training to use this camera effectively. The technical details, the performance and the first images obtained on the telescope with MOCAM are presented. In particular, we discuss some important improvements with respect to the standard single-CCD FOCAM camera, such as multi-output parallel readout and dynamic anti-blooming. We also discuss critical technical issues concerning future wide-field imaging facilities at the CFHT prime focus in light of our experience with MOCAM and our recent experience with the even larger UH 8192x8192 pixel CCD mosaic camera.

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arXiv1996

Clustering around the radio-galaxy MRC0316-257 at z=3.14

We report here the spectroscopic identification of galaxies in the neighborhood of the radio-galaxy MRC0316-257, at a redshift $z\sim3.14$. Candidate cluster galaxies were selected from deep V and I images combined with narrow band imaging at the wavelength of redshifted Ly$α$. Follow-up multi-slit spectroscopy has allowed confirmation of the redshift of the radio-galaxy, $z=3.1420\pm0.0020$, and identification of two associated galaxies at redshifts $z=3.1378\pm0.0028$ and $z=3.1351\pm0.0028$ respectively. The first galaxy is 0.3 $h_{50}^{-1}$ Mpc from the radio-galaxy, is resolved with an intrinsic size $11.6\pm h_{50}^{-1}$ kpc, and shows $Lyα$ in emission with rest $W_{Lyα}=55\pm14$Å. In addition, its extremely blue $V-I$ color might possibly indicate a proto-galaxy forming a first generation of stars in a low dust medium. The second galaxy is 1.3 $h_{50}^{-1}$ Mpc away from the radio-galaxy, is marginally resolved and, in addition to Ly$α$ in emission, shows CIV in emission with a broad component indicating the contribution from an AGN. The comoving density of galaxies with $V<23.8$ and a $Lyα$ flux $>10^{-16}$ ergcm$^{-2}$sec$^{-1}$ in the vicinity of MRC0316-257 is $\sim2.5\times10^{-3}h^3_{50}Mpc^{-3}$, significantly higher than the expected background density of field galaxies with similar properties, and might indicate a rich cluster or proto-cluster environment.

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arXiv1996

The Canada-France Redshift Survey XII: Nature of emission-line field galaxy population up to z = 0.3

We present a spectroscopic study of the 138 field galaxies to a redshift z = 0.3 from the I-selected Canada-France Redshift Survey. 117(85%) spectra exhibit at least H alpha in emission, the remaining 21(15%) are purely absorption-line spectra. We focus our analysis on spectra with H alpha and H beta in emission, accounting for about half of this low-z sample, which we classify using emission-line ratio diagrams. Using photoionization models, we determine the extreme boundaries of H II galaxies in these diagnostic diagrams, and demonstrate that the emission-line ratios of a significant fraction of galaxies require harder photoionization sources than massive O stars. We find that about 17% of the field galaxies have emission-line ratios consistent with active galaxies, e.g., Seyfert 2 or LINERs. After correcting for stellar absorption under the Balmer lines, we conclude that the fraction of such galaxies is at least 8% of the field galaxy population at z < 0.3.

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