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R. Scarpa

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Yale University

University of Melbourne

riccardo scarpa

George Mason University

Alice C. Quillen

University of Rochester

Christopher O'Dea

University of Manitoba

Michela Uslenghi

Istituto Nazionale di Astrofisica

riccardo scarpa

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Papers by R. Scarpa

The HST Survey of BL~ Lacertae Objects. IV. Infrared Imaging of Host Galaxies

The HST NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larg... more The HST NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larger sample observed with the WFPC2 in the R band (Urry et al. 2000; Scarpa et al. 2000). Ten of the 12 BL Lacs are clearly resolved, and the detected host galaxies are large, bright ellipticals with average absolute magnitude M H = −26.2 ± 0.45 mag and effective radius r e = 10 ± 5 kpc. The rest-frame integrated color of the host galaxies is on average R-H = 2.3 ± 0.3, consistent with the value for both radio galaxies and normal, non-active elliptical galaxies, and indicating the dominant stellar population is old. The host galaxies tend to be bluer in their outer regions than in their cores, with average color gradient ∆(R − H)/∆ log r = −0.2 mag, again consistent with results for normal non-active elliptical galaxies. The infrared Kormendy relation, derived for the first time for BL Lac host galaxies, is µ e = 3.8 log r e + 14.8, fully in agreement with the relation for normal ellipticals. The close similarity between BL Lac host galaxies and normal ellipticals suggests the active nucleus has surprisingly little effect on the host galaxy. This supports a picture in which all elliptical galaxies harbor black holes which can be actively accreting for some fraction of their lifetime.

A New Einstein Cross Gravitational Lens of a Lyman-break Galaxy

The Astrophysical Journal, 2019

We report the study of an "Einstein Cross" configuration first identified in a set of HST images ... more We report the study of an "Einstein Cross" configuration first identified in a set of HST images by Cerny et al. (2018). Deep spectroscopic observations obtained at the Spanish 10.4m GTC telescope, allowed us to demonstrate the lens nature of the system, that consists of a Lyman-break galaxy, not a QSO as is usually the case, at z = 3.03 lensed by a galaxy at z=0.556. Combining the new spectroscopy with the archival HST data, it turns out that the lens is an elliptical galaxy with M V = −21.0, effective radius 2.8 kpc and stellar velocity dispersion σ=208±39 km/sec. The source is a Lyman break galaxy with Lyα luminosity ∼ L * at that redshift. From the modeling of the system, performed by assuming a singular isothermal ellipsoid (SIE) with external shear, we estimate that the flux source is magnified about 4.5 times, and the velocity dispersion of the lens is σ SIE = 197.9 +2.6 −1.3 km s −1 , in good agreement with the value derived spectroscopically. This is the second case known of an Einstein cross of a Lyman-break galaxy.

Testing Newtonian gravity in the low acceleration regime with globular clusters: the case ofω Centauri revisited

Astronomy & Astrophysics, 2010

Context. Stellar kinematics in the external regions of globular clusters can be used to probe the... more Context. Stellar kinematics in the external regions of globular clusters can be used to probe the validity of Newton's law in the low acceleration regimes without the complication of non-baryonic dark matter. Indeed, in contrast to the case of galaxies, in globular clusters a systematic deviation of the velocity dispersion profile from the expected Keplerian falloff would be indicative of a breakdown of Newtonian dynamics rather than the existence of dark matter. Aims. We perform a detailed analysis of the velocity dispersion in the globular cluster ω Centauri to determine whether it decreases monotonically with distance as expected within the framework of Newtonian dynamics, or whether it converges toward a constant value as recent works suggest. Methods. We combine measurements from two previous studies to almost double the data available at large radii, to better constrain the velocity dispersion profile in the low acceleration regime. Results. We found the inner region of ω Centauri is clearly rotating, while the rotational velocity tends to vanish, being consistent with no rotation at all in the external regions. The cluster velocity dispersion at large radii from the center is found to clearly deviate from the Newtonian prediction. Conclusions. We conclude that there are strong similarities between globular clusters and elliptical galaxies, for in both classes of objects the velocity dispersion tends to remain constant at large radii. In the case of galaxies, this is ascribed to the existence of a massive halo of dark matter, which is physically unlikely in the case of globular clusters. This similarity, if confirmed, is best explained by a breakdown of Newtonian dynamics below a critical acceleration.

The Cosmic Evolution of Quasar Hosts

ESO Astrophysics Symposia, 2005

We present a study of the M BH-M host relation as a function of Cosmic Time in a sample of ∼ one ... more We present a study of the M BH-M host relation as a function of Cosmic Time in a sample of ∼ one hundred quasars from z = 0 to 3. In this paper we describe the sample, the data sources and the new spectroscopic observations. We then illustrate how we derive M BH from single-epoch spectra, pointing out the uncertainties in the procedure and addressing the role of possible selection biases. In a companion paper, we address the dependence of the ratio between the black hole mass and the host galaxy luminosity and mass on Cosmic Time.

Optical properties of low z radio galaxies

New Astronomy Reviews, 2002

The optical morphological and photometric properties of 79 low redshift radio galaxies are discus... more

Optical photometry and morphology of radio galaxies

The authors report preliminary results on the optical properties (morphology, surface-brightness ... more

Four Gravitational Lens Candidates in The HST Snapshot Survey of BL Lac Objects

BL Lac …, 1999

We report the result of the HST snapshot survey of BL Lac host galaxies. Almost 100 sources with ... more

Optical spectrophotometry of blazars

The Astrophysical Journal Supplement Series, 1994

... via Osservatorio 5, 35122, Padova, Italy AND M. BERSANELLI Istituto di Fisica Cosmica, CNR, v... more

Using globular clusters to test gravity in the weak acceleration regime: NGC 7099

Astronomy & Astrophysics, 2006

Aims. A test of Newton's law of gravity in the low acceleration regime using globular clusters is... more Aims. A test of Newton's law of gravity in the low acceleration regime using globular clusters is presented and new results for the core collapsed globular cluster NGC 7099 given. Methods. The run of the gravitational potential as a function of distance is probed by studying the velocity dispersion profile of the cluster, as derived from a set of 125 radial velocities with accuracy better than 1 km s −1. The velocity dispersion profile is traced up to ∼18 pc from the cluster center. Results. The dispersion is found to be maximal at the center, then decrease until 10 ± 2 pc from the center, well inside the cluster tidal radius of 42 pc. After that the dispersion remains basically constant with an average value of 2.2 ± 0.3 km s −1. Assuming a total V mag of M(V) = −7.43 mag for NGC 7099, the acceleration at 10 ± 2 pc from the center is 1.1 +0.4 −0.3 τ × 10 −8 cm s −2 , where τ is the mass-to-light ratio. Thus, for τ < ∼ 2 typical of globular clusters, the flattening of the velocity dispersion profile occurs for a value of the internal acceleration of gravity that is fully consistent with a 0 = 1.2 × 10 −8 cm s −2 observed in galaxies. Conclusions. This new result for NGC 7099 brings to 4 the clusters with velocity dispersion profile probing acceleration below a 0. All four have been found to have a flat dispersion profile at large radii where the acceleration is below a 0 , thereby mimicking elliptical galaxies qualitatively and quantitatively. Whether this indicates a failure of Newtonian dynamics in the low acceleration limit or some more conventional dynamical effect (e.g., tidal heating) is still unclear. However, the similarities emerging between very different globular clusters, as well as between globular clusters and elliptical galaxies, seem to favor the first of these two possibilities.

Unusual Morphologies from the HST Snapshot Survey of BL Lac Objects: Three Optical Jets and A Possible Einstein Ring

BULLETIN-AMERICAN …, 1999

C. Megan Urry & Riccardo Scarpa Space Telescope Science Institute, 3700 San Martin Dr., Baltimore... more

MOND and the fundamental plane of elliptical galaxies

arXiv (Cornell University), Feb 21, 2003

It is shown that the MOdified Newtonian Dynamics (MOND) explains the tilt of the fundamental plan... more It is shown that the MOdified Newtonian Dynamics (MOND) explains the tilt of the fundamental plane of elliptical galaxies without the need of non-baryonic dark matter. Results found for elliptical galaxies extends to globular clusters and galaxy clusters, showing that MOND agrees with observations over 7 order of magnitude in acceleration.

Optical surface photometry of radio galaxies

Astronomy and Astrophysics Supplement Series, 2000

Optical imaging observations for 50 radio galaxies are presented. For each object isophotal conto... more Optical imaging observations for 50 radio galaxies are presented. For each object isophotal contours, photometric profiles, structural parameters (position angle, ellipticity, Fourier coefficients), and total magnitudes are given. These observations, obtained in the Cousins R band, complement the data presented in a previous paper and are part of a larger project aimed at studying the optical properties of low redshift (z ≤ 0.12) radio galaxies (Govoni et al. 1999). Comments for each individual source are reported.

The Large-scale Environments of Radio Galaxies and BL Lacertae Objects

The study of BL Lac environments is hindered by the lack of knowledge regarding the environments ... more The study of BL Lac environments is hindered by the lack of knowledge regarding the environments of their putative parents, the FRI/II radio galaxies. To rectify this we have assembled a complete sample of FRI/II radio galaxies with z <= 0.15 from the 2 Jy (Wall & Peacock 1985) and Ekers et al. (1989) lists, about 100 objects in total.

Gravitational lens candidates in the HST survey of BL Lac objects

Astrophysics and Space Science, 1999

Without Abstract

Will LCDM cosmology survive the James Webb Space Telescope

Submitted for publication to MNRAS, 2022

The James Webb space telescope (JWST) is about to deliver scientific data. Fundamental contributi... more The James Webb space telescope (JWST) is about to deliver scientific data. Fundamental contributions are expected in all fields of astronomy. Here we focus on the distant Universe, for the JWST is expected to consolidate once and for all the Lambda Cold Dark Matter (LCDM) cosmology. Most crucially, "The End of the Dark Ages: First Light and Reionization" and "The Assembly of Galaxies" are the first two of the four primary JWST Science Goals. Here we critically challenge the general expectations, giving a set of alternatives, presented before they can be either proved or disproved. Our conclusion is that the JWST will provide data incompatible with LCDM cosmology, forcing a revolution both in astronomy and fundamental physics.

UV surface brightness of galaxies from the local universe to z ~ 5

International Journal of Modern Physics D, 2014

The Tolman test for surface brightness (SB) dimming was originally proposed as a test for the exp... more The Tolman test for surface brightness (SB) dimming was originally proposed as a test for the expansion of the universe. The test, which is independent of the details of the assumed cosmology, is based on comparisons of the SB of identical objects at different cosmological distances. Claims have been made that the Tolman test provides compelling evidence against a static model for the universe. In this paper we reconsider this subject by adopting a static Euclidean universe (SEU) with a linear Hubble relation at all z (which is not the standard Einstein–de Sitter model), resulting in a relation between flux and luminosity that is virtually indistinguishable from the one used for ΛCDM models. Based on the analysis of the UV SB of luminous disk galaxies from HUDF and GALEX datasets, reaching from the local universe to z ~ 5, we show that the SB remains constant as expected in a static universe. A re-analysis of previously published data used for the Tolman test at lower redshift, when...

The UV-Optical-Near-IR Emission of BL Lacertae Objects

Multi-Wavelength Continuum Emission of AGN, 1994

Results from UV, optical and near-IR simultaneous observations for 11 BL Lac objects are reported... more Results from UV, optical and near-IR simultaneous observations for 11 BL Lac objects are reported. We find that for all but one source the spectral flux distribution can be described by a single power law (i v oc v~a) plus, where relevant, the contribution of the host galaxy. The comparison of the optical-near-IR and UV spectral indices for two samples of BL Lacs suggests the same picture for a larger sample of objects.

Detection of an X-Ray Jet in 3C 371 with [ITAL]Chandra[/ITAL]

The Astrophysical Journal, 2001

We report the detection at X-rays of the radio/optical jet of 3C 371 from a short (10 ks) Chandra... more We report the detection at X-rays of the radio/optical jet of 3C 371 from a short (10 ks) Chandra exposure in 2000 March. We also present a new MERLIN observation at 1.4 GHz together with a reanalysis of the archival Hubble Space Telescope Wide Field Planetary Camera 2 F555W image. Despite the limited signal-to-noise ratio of the Chandra data, the X-ray morphology is clearly different from that of the radio/optical emission, with the brightest X-ray knot at 1Љ .7 from the nucleus and little X-ray emission from the brightest radio/optical knot at 3Љ .1. We construct the spectral energy distributions for the two emission regions at 1Љ .7 and 3Љ .1. Both show that the X-ray flux is below the extrapolation from the radio-to-optical continuum, suggesting a moderately beamed synchrotron from an electron population with a decreasing high-energy cutoff as a plausible emission mechanism.

TheHubble Space TelescopeSurvey of BL Lacertae Objects. IV. Infrared Imaging of Host Galaxies

The Astrophysical Journal, 2000

The HST NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larg... more The HST NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larger sample observed with the WFPC2 in the R band (Urry et al. 2000; Scarpa et al. 2000). Ten of the 12 BL Lacs are clearly resolved, and the detected host galaxies are large, bright ellipticals with average absolute magnitude M H = −26.2 ± 0.45 mag and effective radius r e = 10 ± 5 kpc. The rest-frame integrated color of the host galaxies is on average R-H = 2.3 ± 0.3, consistent with the value for both radio galaxies and normal, non-active elliptical galaxies, and indicating the dominant stellar population is old. The host galaxies tend to be bluer in their outer regions than in their cores, with average color gradient ∆(R − H)/∆ log r = −0.2 mag, again consistent with results for normal non-active elliptical galaxies. The infrared Kormendy relation, derived for the first time for BL Lac host galaxies, is µ e = 3.8 log r e + 14.8, fully in agreement with the relation for normal ellipticals. The close similarity between BL Lac host galaxies and normal ellipticals suggests the active nucleus has surprisingly little effect on the host galaxy. This supports a picture in which all elliptical galaxies harbor black holes which can be actively accreting for some fraction of their lifetime.

The near-infrared-optical-ultraviolet emission of BL Lacertae objects

The Astrophysical Journal, 1994

Near-infrared, optical and ultraviolet quasi-simultaneous observations of 11 BL Lacertae objects ... more Near-infrared, optical and ultraviolet quasi-simultaneous observations of 11 BL Lacertae objects are reported. For all but one source the dereddened spectral flux distribution in the 8 • 10 13 -2 • 10 15 Hz frequency range can be described by a single power law f ν ∝ ν -α with average spectral index < α > = 0.88 ± 0.42 (standard deviation) plus, where relevant, the contribution of the host galaxy. In most cases the non simultaneous soft X-ray fluxes obtained by the Einstein Observatory lie on or below the extrapolation of the power law. The results are compared with the average spectral properties of other samples of BL Lacs studied separately in the IR-optical and in the UV bands. The implications for existing models of the objects are shortly discussed.

The HST Survey of BL~ Lacertae Objects. IV. Infrared Imaging of Host Galaxies

The HST NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larg... more The HST NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larger sample observed with the WFPC2 in the R band (Urry et al. 2000; Scarpa et al. 2000). Ten of the 12 BL Lacs are clearly resolved, and the detected host galaxies are large, bright ellipticals with average absolute magnitude M H = −26.2 ± 0.45 mag and effective radius r e = 10 ± 5 kpc. The rest-frame integrated color of the host galaxies is on average R-H = 2.3 ± 0.3, consistent with the value for both radio galaxies and normal, non-active elliptical galaxies, and indicating the dominant stellar population is old. The host galaxies tend to be bluer in their outer regions than in their cores, with average color gradient ∆(R − H)/∆ log r = −0.2 mag, again consistent with results for normal non-active elliptical galaxies. The infrared Kormendy relation, derived for the first time for BL Lac host galaxies, is µ e = 3.8 log r e + 14.8, fully in agreement with the relation for normal ellipticals. The close similarity between BL Lac host galaxies and normal ellipticals suggests the active nucleus has surprisingly little effect on the host galaxy. This supports a picture in which all elliptical galaxies harbor black holes which can be actively accreting for some fraction of their lifetime.

A New Einstein Cross Gravitational Lens of a Lyman-break Galaxy

The Astrophysical Journal, 2019

We report the study of an "Einstein Cross" configuration first identified in a set of HST images ... more We report the study of an "Einstein Cross" configuration first identified in a set of HST images by Cerny et al. (2018). Deep spectroscopic observations obtained at the Spanish 10.4m GTC telescope, allowed us to demonstrate the lens nature of the system, that consists of a Lyman-break galaxy, not a QSO as is usually the case, at z = 3.03 lensed by a galaxy at z=0.556. Combining the new spectroscopy with the archival HST data, it turns out that the lens is an elliptical galaxy with M V = −21.0, effective radius 2.8 kpc and stellar velocity dispersion σ=208±39 km/sec. The source is a Lyman break galaxy with Lyα luminosity ∼ L * at that redshift. From the modeling of the system, performed by assuming a singular isothermal ellipsoid (SIE) with external shear, we estimate that the flux source is magnified about 4.5 times, and the velocity dispersion of the lens is σ SIE = 197.9 +2.6 −1.3 km s −1 , in good agreement with the value derived spectroscopically. This is the second case known of an Einstein cross of a Lyman-break galaxy.

Testing Newtonian gravity in the low acceleration regime with globular clusters: the case ofω Centauri revisited

Astronomy & Astrophysics, 2010

Context. Stellar kinematics in the external regions of globular clusters can be used to probe the... more Context. Stellar kinematics in the external regions of globular clusters can be used to probe the validity of Newton's law in the low acceleration regimes without the complication of non-baryonic dark matter. Indeed, in contrast to the case of galaxies, in globular clusters a systematic deviation of the velocity dispersion profile from the expected Keplerian falloff would be indicative of a breakdown of Newtonian dynamics rather than the existence of dark matter. Aims. We perform a detailed analysis of the velocity dispersion in the globular cluster ω Centauri to determine whether it decreases monotonically with distance as expected within the framework of Newtonian dynamics, or whether it converges toward a constant value as recent works suggest. Methods. We combine measurements from two previous studies to almost double the data available at large radii, to better constrain the velocity dispersion profile in the low acceleration regime. Results. We found the inner region of ω Centauri is clearly rotating, while the rotational velocity tends to vanish, being consistent with no rotation at all in the external regions. The cluster velocity dispersion at large radii from the center is found to clearly deviate from the Newtonian prediction. Conclusions. We conclude that there are strong similarities between globular clusters and elliptical galaxies, for in both classes of objects the velocity dispersion tends to remain constant at large radii. In the case of galaxies, this is ascribed to the existence of a massive halo of dark matter, which is physically unlikely in the case of globular clusters. This similarity, if confirmed, is best explained by a breakdown of Newtonian dynamics below a critical acceleration.

The Cosmic Evolution of Quasar Hosts

ESO Astrophysics Symposia, 2005

We present a study of the M BH-M host relation as a function of Cosmic Time in a sample of ∼ one ... more We present a study of the M BH-M host relation as a function of Cosmic Time in a sample of ∼ one hundred quasars from z = 0 to 3. In this paper we describe the sample, the data sources and the new spectroscopic observations. We then illustrate how we derive M BH from single-epoch spectra, pointing out the uncertainties in the procedure and addressing the role of possible selection biases. In a companion paper, we address the dependence of the ratio between the black hole mass and the host galaxy luminosity and mass on Cosmic Time.

Optical properties of low z radio galaxies

New Astronomy Reviews, 2002

The optical morphological and photometric properties of 79 low redshift radio galaxies are discus... more

Optical photometry and morphology of radio galaxies

The authors report preliminary results on the optical properties (morphology, surface-brightness ... more

Four Gravitational Lens Candidates in The HST Snapshot Survey of BL Lac Objects

BL Lac …, 1999

We report the result of the HST snapshot survey of BL Lac host galaxies. Almost 100 sources with ... more

Optical spectrophotometry of blazars

The Astrophysical Journal Supplement Series, 1994

... via Osservatorio 5, 35122, Padova, Italy AND M. BERSANELLI Istituto di Fisica Cosmica, CNR, v... more

Using globular clusters to test gravity in the weak acceleration regime: NGC 7099

Astronomy & Astrophysics, 2006

Aims. A test of Newton's law of gravity in the low acceleration regime using globular clusters is... more Aims. A test of Newton's law of gravity in the low acceleration regime using globular clusters is presented and new results for the core collapsed globular cluster NGC 7099 given. Methods. The run of the gravitational potential as a function of distance is probed by studying the velocity dispersion profile of the cluster, as derived from a set of 125 radial velocities with accuracy better than 1 km s −1. The velocity dispersion profile is traced up to ∼18 pc from the cluster center. Results. The dispersion is found to be maximal at the center, then decrease until 10 ± 2 pc from the center, well inside the cluster tidal radius of 42 pc. After that the dispersion remains basically constant with an average value of 2.2 ± 0.3 km s −1. Assuming a total V mag of M(V) = −7.43 mag for NGC 7099, the acceleration at 10 ± 2 pc from the center is 1.1 +0.4 −0.3 τ × 10 −8 cm s −2 , where τ is the mass-to-light ratio. Thus, for τ < ∼ 2 typical of globular clusters, the flattening of the velocity dispersion profile occurs for a value of the internal acceleration of gravity that is fully consistent with a 0 = 1.2 × 10 −8 cm s −2 observed in galaxies. Conclusions. This new result for NGC 7099 brings to 4 the clusters with velocity dispersion profile probing acceleration below a 0. All four have been found to have a flat dispersion profile at large radii where the acceleration is below a 0 , thereby mimicking elliptical galaxies qualitatively and quantitatively. Whether this indicates a failure of Newtonian dynamics in the low acceleration limit or some more conventional dynamical effect (e.g., tidal heating) is still unclear. However, the similarities emerging between very different globular clusters, as well as between globular clusters and elliptical galaxies, seem to favor the first of these two possibilities.

Unusual Morphologies from the HST Snapshot Survey of BL Lac Objects: Three Optical Jets and A Possible Einstein Ring

BULLETIN-AMERICAN …, 1999

C. Megan Urry & Riccardo Scarpa Space Telescope Science Institute, 3700 San Martin Dr., Baltimore... more

MOND and the fundamental plane of elliptical galaxies

arXiv (Cornell University), Feb 21, 2003

It is shown that the MOdified Newtonian Dynamics (MOND) explains the tilt of the fundamental plan... more It is shown that the MOdified Newtonian Dynamics (MOND) explains the tilt of the fundamental plane of elliptical galaxies without the need of non-baryonic dark matter. Results found for elliptical galaxies extends to globular clusters and galaxy clusters, showing that MOND agrees with observations over 7 order of magnitude in acceleration.

Optical surface photometry of radio galaxies

Astronomy and Astrophysics Supplement Series, 2000

Optical imaging observations for 50 radio galaxies are presented. For each object isophotal conto... more Optical imaging observations for 50 radio galaxies are presented. For each object isophotal contours, photometric profiles, structural parameters (position angle, ellipticity, Fourier coefficients), and total magnitudes are given. These observations, obtained in the Cousins R band, complement the data presented in a previous paper and are part of a larger project aimed at studying the optical properties of low redshift (z ≤ 0.12) radio galaxies (Govoni et al. 1999). Comments for each individual source are reported.

The Large-scale Environments of Radio Galaxies and BL Lacertae Objects

The study of BL Lac environments is hindered by the lack of knowledge regarding the environments ... more The study of BL Lac environments is hindered by the lack of knowledge regarding the environments of their putative parents, the FRI/II radio galaxies. To rectify this we have assembled a complete sample of FRI/II radio galaxies with z <= 0.15 from the 2 Jy (Wall & Peacock 1985) and Ekers et al. (1989) lists, about 100 objects in total.

Gravitational lens candidates in the HST survey of BL Lac objects

Astrophysics and Space Science, 1999

Without Abstract

Will LCDM cosmology survive the James Webb Space Telescope

Submitted for publication to MNRAS, 2022

The James Webb space telescope (JWST) is about to deliver scientific data. Fundamental contributi... more The James Webb space telescope (JWST) is about to deliver scientific data. Fundamental contributions are expected in all fields of astronomy. Here we focus on the distant Universe, for the JWST is expected to consolidate once and for all the Lambda Cold Dark Matter (LCDM) cosmology. Most crucially, "The End of the Dark Ages: First Light and Reionization" and "The Assembly of Galaxies" are the first two of the four primary JWST Science Goals. Here we critically challenge the general expectations, giving a set of alternatives, presented before they can be either proved or disproved. Our conclusion is that the JWST will provide data incompatible with LCDM cosmology, forcing a revolution both in astronomy and fundamental physics.

UV surface brightness of galaxies from the local universe to z ~ 5

International Journal of Modern Physics D, 2014

The Tolman test for surface brightness (SB) dimming was originally proposed as a test for the exp... more The Tolman test for surface brightness (SB) dimming was originally proposed as a test for the expansion of the universe. The test, which is independent of the details of the assumed cosmology, is based on comparisons of the SB of identical objects at different cosmological distances. Claims have been made that the Tolman test provides compelling evidence against a static model for the universe. In this paper we reconsider this subject by adopting a static Euclidean universe (SEU) with a linear Hubble relation at all z (which is not the standard Einstein–de Sitter model), resulting in a relation between flux and luminosity that is virtually indistinguishable from the one used for ΛCDM models. Based on the analysis of the UV SB of luminous disk galaxies from HUDF and GALEX datasets, reaching from the local universe to z ~ 5, we show that the SB remains constant as expected in a static universe. A re-analysis of previously published data used for the Tolman test at lower redshift, when...

The UV-Optical-Near-IR Emission of BL Lacertae Objects

Multi-Wavelength Continuum Emission of AGN, 1994

Results from UV, optical and near-IR simultaneous observations for 11 BL Lac objects are reported... more Results from UV, optical and near-IR simultaneous observations for 11 BL Lac objects are reported. We find that for all but one source the spectral flux distribution can be described by a single power law (i v oc v~a) plus, where relevant, the contribution of the host galaxy. The comparison of the optical-near-IR and UV spectral indices for two samples of BL Lacs suggests the same picture for a larger sample of objects.

Detection of an X-Ray Jet in 3C 371 with [ITAL]Chandra[/ITAL]

The Astrophysical Journal, 2001

We report the detection at X-rays of the radio/optical jet of 3C 371 from a short (10 ks) Chandra... more We report the detection at X-rays of the radio/optical jet of 3C 371 from a short (10 ks) Chandra exposure in 2000 March. We also present a new MERLIN observation at 1.4 GHz together with a reanalysis of the archival Hubble Space Telescope Wide Field Planetary Camera 2 F555W image. Despite the limited signal-to-noise ratio of the Chandra data, the X-ray morphology is clearly different from that of the radio/optical emission, with the brightest X-ray knot at 1Љ .7 from the nucleus and little X-ray emission from the brightest radio/optical knot at 3Љ .1. We construct the spectral energy distributions for the two emission regions at 1Љ .7 and 3Љ .1. Both show that the X-ray flux is below the extrapolation from the radio-to-optical continuum, suggesting a moderately beamed synchrotron from an electron population with a decreasing high-energy cutoff as a plausible emission mechanism.

TheHubble Space TelescopeSurvey of BL Lacertae Objects. IV. Infrared Imaging of Host Galaxies

The Astrophysical Journal, 2000

The HST NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larg... more The HST NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larger sample observed with the WFPC2 in the R band (Urry et al. 2000; Scarpa et al. 2000). Ten of the 12 BL Lacs are clearly resolved, and the detected host galaxies are large, bright ellipticals with average absolute magnitude M H = −26.2 ± 0.45 mag and effective radius r e = 10 ± 5 kpc. The rest-frame integrated color of the host galaxies is on average R-H = 2.3 ± 0.3, consistent with the value for both radio galaxies and normal, non-active elliptical galaxies, and indicating the dominant stellar population is old. The host galaxies tend to be bluer in their outer regions than in their cores, with average color gradient ∆(R − H)/∆ log r = −0.2 mag, again consistent with results for normal non-active elliptical galaxies. The infrared Kormendy relation, derived for the first time for BL Lac host galaxies, is µ e = 3.8 log r e + 14.8, fully in agreement with the relation for normal ellipticals. The close similarity between BL Lac host galaxies and normal ellipticals suggests the active nucleus has surprisingly little effect on the host galaxy. This supports a picture in which all elliptical galaxies harbor black holes which can be actively accreting for some fraction of their lifetime.

The near-infrared-optical-ultraviolet emission of BL Lacertae objects

The Astrophysical Journal, 1994

Near-infrared, optical and ultraviolet quasi-simultaneous observations of 11 BL Lacertae objects ... more Near-infrared, optical and ultraviolet quasi-simultaneous observations of 11 BL Lacertae objects are reported. For all but one source the dereddened spectral flux distribution in the 8 • 10 13 -2 • 10 15 Hz frequency range can be described by a single power law f ν ∝ ν -α with average spectral index < α > = 0.88 ± 0.42 (standard deviation) plus, where relevant, the contribution of the host galaxy. In most cases the non simultaneous soft X-ray fluxes obtained by the Einstein Observatory lie on or below the extrapolation of the power law. The results are compared with the average spectral properties of other samples of BL Lacs studied separately in the IR-optical and in the UV bands. The implications for existing models of the objects are shortly discussed.