arXiv subjects

P. Martini

Publications and source records attributed to P. Martini.

215 records · Page 12Linked to original sources

arXiv2011

Black Hole Mass Estimates Based on CIV are Consistent with Those Based on the Balmer Lines

Using a sample of high-redshift lensed quasars from the CASTLES project with observed-frame ultraviolet or optical and near-infrared spectra, we have searched for possible biases between supermassive black hole (BH) mass estimates based on the CIV, Halpha and Hbeta broad emission lines. Our sample is based upon that of Greene, Peng & Ludwig, expanded with new near-IR spectroscopic observations, consistently analyzed high S/N optical spectra, and consistent continuum luminosity estimates at 5100A. We find that BH mass estimates based on the FWHM of CIV show a systematic offset with respect to those obtained from the line dispersion, sigma_l, of the same emission line, but not with those obtained from the FWHM of Halpha and Hbeta. The magnitude of the offset depends on the treatment of the HeII and FeII emission blended with CIV, but there is little scatter for any fixed measurement prescription. While we otherwise find no systematic offsets between CIV and Balmer line mass estimates, we do find that the residuals between them are strongly correlated with the ratio of the UV and optical continuum luminosities. Removing this dependency reduces the scatter between the UV- and optical-based BH mass estimates by a factor of approximately 2, from roughly 0.35 to 0.18 dex. The dispersion is smallest when comparing the CIV sigma_l mass estimate, after removing the offset from the FWHM estimates, and either Balmer line mass estimate. The correlation with the continuum slope is likely due to a combination of reddening, host contamination and object-dependent SED shapes. When we add additional heterogeneous measurements from the literature, the results are unchanged.

astro-ph.CO↗

arXiv2010

Pre-discovery and Follow-up Observations of the Nearby SN 2009nr: Implications for Prompt Type Ia SNe

We present photometric and spectroscopic observations of the Type Ia supernova SN 2009nr in UGC 8255 (z=0.0122). Following the discovery announcement at what turned out to be ten days after peak, we detected it at V ~15.7 mag in data collected by the All Sky Automated Survey (ASAS) North telescope 2 weeks prior to the peak, and then followed it up with telescopes ranging in aperture from 10-cm to 6.5-m. Using early photometric data available only from ASAS, we find that the SN is similar to the over-luminous Type Ia SN 1991T, with a peak at Mv=-19.6 mag, and a slow decline rate of Dm_15(B)=0.95 mag. The early post-maximum spectra closely resemble those of SN 1991T, while the late time spectra are more similar to those of normal Type Ia SNe. Interestingly, SN 2009nr has a projected distance of 13.0 kpc (~4.3 disk scale lengths) from the nucleus of the small star-forming host galaxy UGC 8255. This indicates that the progenitor of SN 2009nr is not associated with a young stellar population, calling into question the conventional association of luminous SNe Ia with the "prompt" component directly correlated with current star formation. The pre-discovery observation of SN 2009nr using ASAS demonstrates the science utility of high cadence all sky surveys conducted using small telescopes for the discovery of nearby (d=<50 Mpc) supernovae.

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arXiv2010

Abell 611: I. weak lensing analysis with LBC

Aims. The Large Binocular Cameras (LBC) are two twin wide field cameras (FOV ~ 23'x 25') mounted at the prime foci of the 8.4m Large Binocular Telescope (LBT). We performed a weak lensing analysis of the z=0.288 cluster Abell 611 on g-band data obtained by the blue-optimized Large Binocular Camera in order to estimate the cluster mass. Methods. Due to the complexity of the PSF of LBC, we decided to use two different approaches, KSB and Shapelets, to measure the shape of background galaxies and to derive the shear signal produced by the cluster. Then we estimated the cluster mass with both aperture densitometry and parametric model fits. Results. The combination of the large aperture of the telescope and the wide field of view allowed us to map a region well beyond the expected virial radius of the cluster and to get a high surface density of background galaxies (23 galaxies/arcmin^2). This made possible to estimate an accurate mass for Abell 611. We find that the mass within 1.5 Mpc is: $(8\pm3)\times 10^{14} M_\odot$ from the aperture mass technique and $(5\pm1)\times 10^{14} M_\odot$ using the model fitting by a NFW mass density profile, for both Shapelets and KSB methods. This analysis demonstrates that LBC is a powerful instrument for weak gravitational lensing studies.

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arXiv2009

Feeding versus Feedback in NGC4151 probed with Gemini NIFS. II. Kinematics

We have used the Gemini NIFS to map the gas kinematics of the inner 200x500pc of the Seyfert galaxy NGC4151 in the Z, J, H and K bands at a resolving power 5000 and spatial resolution of 8pc. The ionised gas emission is most extended along the known ionisation bi-cone at position angle PA=60-240deg, but is observed also along its equatorial plane. This indicates that the AGN ionizes gas beyond the borders of the bi-cone, within a sphere with 1arcsec radius around the nucleus. The ionised gas has three kinematic components: (1) one observed at the systemic velocity and interpreted as originating in the galaxy disk; (2) one outflowing along the bi-cone, with line-of-sight velocities between -600 and 600 km/s and strongest emission at +/-(100-300)km/s; (3) and another component due to the interaction of the radio jet with ambient gas. The mass outflow rate, estimated to be 1 M_Sun/yr along each cone, exceeds the inferred black hole accretion rate by a factor of 100. There is no evidence in our data for the gradual acceleration followed by gradual deceleration proposed by previous modelling of the [OIII] emitting gas. The molecular gas exhiibits distinct kinematics relative to the ionised gas. Its emission arises in extended regions approximately perpendicular to the axis of the bi-cone and along the axis of the galaxy's stellar bar, avoiding the innermost ionised regions. It does not show an outflowing component, being observed only at velocities very close to systemic, and is thus consistent with an origin in the galaxy plane. This hot molecular gas may only be the tracer of a larger reservoir of colder gas which represents the AGN feeding.

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arXiv2009

Feeding and Feedback in NGC 4151 from GEMINI Near Infrared Integral Field Spectroscopy

We discuss two-dimensional mapping of the near-infrared emission-line intensity distributions and kinematics of the narrow-line region (NLR) of NGC 4151, obtained with the Gemini Near-Infrared Integral Field Spectrograph, with a projected spatial resolution of ~8pc. The ionized gas intensity distribution follows the projected bi-cone morphology observed in previous optical narrow-band images, and its kinematics reveal outflows along the bi-cone. We propose a kinematic model in which the gas in the NLR moves at a velocity of ~600 km s^-1 up to ~100 pc from the nucleus. A completely distinct morphology and kinematic structure is observed for the molecular gas, which avoids the region of the bi-cone and has velocities close to systemic, and is consistent with an origin in the galaxy plane. The molecular gas thus traces the AGN feeding, while the ionized gas traces its feedback.

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arXiv2009

An Analysis of DES Cluster Simulations through the IMCAT and Shapelets Weak Lensing Pipelines

We have run two completely independent weak lensing analysis pipelines on a set of realistic simulated images of a massive galaxy cluster with a singular isothermal sphere profile (galaxy velocity dispersion sigma_v=1250 km/ sec). The suite of images was constructed using the simulation tools developed by the Dark Energy Survey. We find that both weak lensing pipelines can accurately recover the velocity dispersion of our simulated clusters, suggesting that current weak lensing tools are accurate enough for measuring the shear profile of massive clusters in upcoming large photometric surveys. We also demonstrate how choices of some cuts influence the final shear profile and sigma_v measurement. Analogously to the STEP program, we make all of these cluster simulation images publically available for other groups to analyze through their own weak lensing pipelines.

astro-ph.IM↗

arXiv2008

Discovery of the Dust-Enshrouded Progenitor of SN 2008S with Spitzer

We report the discovery of the progenitor of the recent type IIn SN 2008S in the nearby galaxy NGC 6946. Surprisingly, it was not found in deep, pre-explosion optical images of its host galaxy taken with the Large Binocular Telescope, but only through examination of archival Spitzer mid-IR data. A source coincident with the SN 2008S position is clearly detected in the 4.5, 5.8, and 8.0 micron IRAC bands, showing no evident variability in the three years prior to the explosion, yet is undetected at 3.6 and 24 micron. The distinct presence of ~440 K dust, along with stringent LBT limits on the optical fluxes, suggests that the progenitor of SN 2008S was engulfed in a shroud of its own dust. The inferred luminosity of 3.5x10^4 Lsun implies a modest mass of ~10 Msun. We conclude that objects like SN 2008S are not exclusively associated with the deaths or outbursts of very massive eta Carinae-like objects. This conclusion holds based solely on the optical flux limits even if our identification of the progenitor with the mid-IR source is incorrect.

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arXiv2005

The Fundamental Scaling Relations of Elliptical Galaxies

(ABRIDGED) We examine the fundamental scaling relations of elliptical galaxies formed through mergers. Using hundreds of simulations to judge the impact of progenitor galaxy properties on merger remnants, we find that gas dissipation provides an important contribution to tilt in the Fundamental Plane relation. Dissipationless mergers of disks produce remnants that occupy the virial plane. As the gas content of disk galaxies is increased, the tilt of the Fundamental Plane relation increases and the slope of the Re-M_* relation steepens. For gas fractions fgas > 30%, the simulated Fundamental Plane scalings approach those observed in the K-band. In our simulations, feedback from supermassive black hole growth has only a minor influence on the stellar-mass scaling relations of spheroidal galaxies, but may play a role in maintaining the observed Fundamental Plane tilt at optical wavelengths by suppressing residual star formation in merger remnants. We estimate that \approx 40-100% of the Fundamental Plane tilt induced by structural properties owes to trends in the central total-to-stellar mass ratio M_total/M_* produced by dissipation. Lower mass systems obtain greater phase- space densities than higher mass systems, producing a galaxy mass-dependent central M_total/M_* and a corresponding tilt in the Fundamental Plane.

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arXiv2003

Iron Emission in the z=6.4 Quasar SDSS J114816.64+525150.3

We present near-infrared J and K-band spectra of the z = 6.4 quasar SDSS J114816.64+525150.3 obtained with the NIRSPEC spectrograph at the Keck-II telescope, covering the rest-frame spectral regions surrounding the C IV 1549 and Mg II 2800 emission lines. The iron emission blend at rest wavelength 2900-3000 A is clearly detected and its strength appears nearly indistinguishable from that of typical quasars at lower redshifts. The Fe II / Mg II ratio is also similar to values found for lower-redshift quasars, demonstrating that there is no strong evolution in Fe/alpha broad-line emission ratios even out to z=6.4. In the context of current models for iron enrichment from Type Ia supernovae, this implies that the SN Ia progenitor stars formed at z > 10. We apply the scaling relations of Vestergaard and of McLure & Jarvis to estimate the black hole mass from the widths of the C IV and Mg II emission lines and the ultraviolet continuum luminosity. The derived mass is in the range (2-6)x10^9 solar masses, with an additional uncertainty of a factor of 3 due to the intrinsic scatter in the scaling relations. This result is in agreement with the previous mass estimate of 3x10^9 solar masses by Willott, McLure, & Jarvis, and supports their conclusion that the quasar is radiating close to its Eddington luminosity.

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arXiv2003

Spectroscopic Discovery of the Supernova 2003dh Associated with GRB 030329

We present early observations of the afterglow of the Gamma-Ray Burst (GRB) 030329 and the spectroscopic discovery of its associated supernova SN 2003dh. We obtained spectra of the afterglow of GRB 030329 each night from March 30.12 (0.6 days after the burst) to April 8.13 (UT) (9.6 days after the burst). The spectra cover a wavelength range of 350 nm to 850 nm. The early spectra consist of a power-law continuum (F_nu ~ nu^{-0.9}) with narrow emission lines originating from HII regions in the host galaxy, indicating a low redshift of z=0.1687. However, our spectra taken after 2003 Apr. 5 show broad peaks in flux characteristic of a supernova. Correcting for the afterglow emission, we find the spectrum of the supernova is remarkably similar to the type Ic `hypernova' SN 1998bw. While the presence of supernovae have been inferred from the light curves and colors of GRB afterglows in the past, this is the first direct, spectroscopic confirmation that a subset of classical gamma-ray bursts originate from supernovae.

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arXiv2002

The Las Campanas Infrared Survey. IV. The Photometric Redshift Survey and the Rest-frame R-band Galaxy Luminosity Function at 0.5 <= z <= 1.5

(Abridged) We present rest-frame R-band galaxy luminosity function measurements for three different redshift ranges: 0.5<=z<=0.75, 0.75<=z<=1.0, and 1.0<=z<=1.5. Our measurements are based on photometric redshifts for ~3000 H-band selected galaxies with apparent magnitudes 17<=H<=20 from the Las Campanas Infrared Survey. We show that our photometric redshifts are accurate with an RMS dispersion between the photometric and spectroscopic redshifts of σ_z/(1+z)~0.08. Using galaxies identified in the Hubble Deep Field South and Chandra Deep Field South regions, we find, respectively, that (7.3\pm 0.2) % and (16.7\pm 0.4)% of the H<=20 galaxies are at z>=1. We first demonstrate that the systematic uncertainty inherent in the luminosity function measurements due to uncertainties in photometric redshifts is non-negligible and therefore must be accounted for. We then develop a technique to correct for this systematic error by incorporating the redshift error functions of individual galaxies in the luminosity function analysis. The redshift error functions account for the non-gaussian characteristics of photometric redshift uncertainties. They are the products of a convolution between the corresponding redshift likelihood functions of individual galaxies and a Gaussian distribution function that characterizes template-mismatch variance. We demonstrate, based on a Monte Carlo simulation, that we are able to completely recover the bright end of the intrinsic galaxy luminosity function using this technique. Finally, we calculate the luminosity function separately for the total H-band selected sample and for a sub-sample of early-type galaxies that have a best-fit spectral type of E/S0 or Sab from the photometric redshift analysis.

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arXiv2002

BL Lac Identification for the Ultraluminous X-ray Source Observed in the Direction of NGC 4698

We report the identification of the optical and radio counterparts of the ultraluminous X-ray (ULX) source XMMU J124825.9+083020 (NGC4698-ULX1). The optical spectrum taken with the VLT yields a redshift of z=0.43, which implies that the ULX is not associated with the nearby galaxy NGC4698. The spectral energy distribution calculated from the available data indicates that the source is likely to be a BL Lac object. The possible synchrotron peak at X-ray energies suggests that this source may be a gamma-ray emitter.

astro-ph↗

arXiv2001

The Las Campanas Infrared Survey. III. The H-band Imaging Survey and the Near-Infrared and Optical Photometric Catalogs

(Abridged) The Las Campanas Infrared Survey, based on broad-band optical and near-infrared photometry, is designed to robustly identify a statistically significant and representative sample of evolved galaxies at redshifts z>1. We have completed an H-band imaging survey over 1.1 square degrees of sky in six separate fields. The average 5 sigma detection limit in a four arcsecond diameter aperture is H ~ 20. Here we describe the design of the survey, the observation strategies, data reduction techniques, and object identification procedures. We present sample near-infrared and optical photometric catalogs for objects identified in two survey fields. We perform object detection in all bandpasses and identify ~ 54,000 galaxies over 1,408 square arcminutes of sky in the two fields. Of these galaxies, ~ 14,000 are detected in the H-band and ~ 2,000 have the colors of evolved galaxies, I - H >3, at z > 1. We find that (1) the differential number counts N(m) for the H-band detected objects has a slope of 0.44 at H < 19 and 0.27 for H > 19. In addition, we find that (2) the differential number counts for the H detected red objects has a slope of 0.85 at H < 20 and 0.32 at H > 20, with a mean surface density ~ 3,000 degree^{-2} mag^{-1} at H=20. Finally, we find that (3) galaxies with red optical to near-IR colors (I-H > 3) constitute ~ 20% of the H detected galaxies at H ~ 21, but only 2% at H = 19. We show that red galaxies are strongly clustered, which results in a strong field to field variation in their surface density. Comparisons of observations and predictions based on various formation scenarios indicate that these red galaxies are consistent with mildly evolving early-type galaxies at z ~ 1, although with a significant amount of on-going star formation as indicated by the large scatter in their V-I colors.

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arXiv2001

The z ~ 1.2 Galaxy Luminosity Function from The LCIR Survey

We present results from the Las Campanas Infrared Survey, designed to identify a statistically significant sample of z>=1 galaxies using photometric redshift techniques. Here we summarize the design and strategies of the survey and present the first estimate of the galaxy luminosity function at z>=1 based on H-band selected galaxies identified in our survey. Results of number count studies and luminosity function measurements indicate that most early-type galaxies were already in place by z~1.2 with a modest space density evolution and a mild luminosity evolution over that expected from passive evolution.

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arXiv2001

The Las Campanas IR Survey: Early Type Galaxy Progenitors Beyond Redshift One

(Abridged) We have identified a population of faint red galaxies from a 0.62 square degree region of the Las Campanas Infrared Survey whose properties are consistent with their being the progenitors of early-type galaxies. The optical and IR colors, number-magnitude relation and angular clustering together indicate modest evolution and increased star formation rates among the early-type field population at redshifts between one and two. The counts of red galaxies with $H$ magnitudes between 17 and 20 rise with a slope that is much steeper than that of the total H sample. The surface density of red galaxies drops from roughly 3000 per square degree at H = 20.5, I-H > 3 to ~ 20 per square degree at H = 20, I-H > 5. The V-I colors are approximately 1.5 magnitudes bluer on average than a pure old population and span a range of more than three magnitudes. The colors, and photometric redshifts derived from them, indicate that the red galaxies have redshift distributions adequately described by Gaussians with sigma_z ~ 0.2$ centered near redshift one, with the exception that galaxies having $V-I<1.6$ and $I-H>3$ are primarily in the 1.5 < z < 2 range. We find co-moving correlation lengths of 9-10 Mpc at z ~ 1, comparable to, or larger than, those found for early-type galaxies at lower redshifts. A simple photometric evolution model reproduces the counts of the red galaxies, with only a ~ 30% decline in the underlying space density of early-type galaxies at z ~ 1.2. We suggest on the basis of the colors, counts, and clustering that these red galaxies are the bulk of the progenitors of present day early-type galaxies.

astro-ph↗

arXiv2001

Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Akn 564. III. Optical Observations and the Optical--UV--X-ray Connection

We present the results of a two-year long optical monitoring program of the narrow-line Seyfert 1 galaxy Akn 564. The majority of this monitoring project was also covered by X-ray observations (RXTE) and for a period of ~50 days, we observed the galaxy in UV (HST) and X-rays (RXTE & ASCA) simultaneously with the ground-based observations. Rapid and large-amplitude variations seen in the X-ray band, on a daily and hourly time-scale, were not detected at optical and UV wavelengths, which in turn exhibited much lower variability either on short (one day) or long (several months) time-scales. The only significant optical variations can be described as two 2--4 day events with ~10% flux variations. We detect no significant optical line variations and thus cannot infer a reverberation size for the broad-line region. Similarly, the large X-ray variations seem to vanish when the light curve is smoothed over a period of 30 days. The UV continuum follows the X-rays with a lag of ~0.4 days, and the optical band lags the UV band by ~2 days. No significant correlation was found between the entire X-ray dataset and the optical band. Focusing on a 20-day interval around the strongest optical event we detect a significant X-ray--optical correlation with similar events seen in the UV and X-rays. Our data are consistent with reprocessing models on the grounds of the energy emitted in this single event. However, several large X-ray flares produced no corresponding optical emission.

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arXiv1997

Multi-Wavelength Monitoring of GRS 1915+105

Since its discovery in 1992, the superluminal X-ray transient GRS 1915+105 has been extensively observed in an attempt to understand its behaviour. We present here first results from a multi-wavelength campaign undertaken from July to September 1996. This study includes X-ray data from the RXTE All Sky Monitor and BATSE, two-frequency data from the Nancay radio telescope, and infrared photometry from the 1.8m Perkins telescope at Lowell Observatory. The first long-term well-sampled IR light curve of GRS 1915+105 is presented herein and is consistent with the interpretation of this source as a long-period binary. We compare the various light curves, searching for correlations in the behaviour of the source at differing wavelengths and for possible periodicities.

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