Peter Erwin - Academia.edu (original) (raw)

Papers by Peter Erwin

Research paper thumbnail of Hα Surface Brightness Profiles of Star-Forming Galaxies and Dependence on Halo Mass Using the HAGGIS Survey

We present the first results from the Hα Galaxy Groups Imaging Survey (HAGGIS), a narrow-band ima... more We present the first results from the Hα Galaxy Groups Imaging Survey (HAGGIS), a narrow-band imaging survey of SDSS groups at z < 0.05 conducted using the Wide Field Imager (WFI) on the ESO/MPG 2.2-meter telescope and the Wide Field Camera (WFC) on the Issac Newton Telescope (INT). In total, we observed 100 galaxy groups with a wide range of halo mass (1012 - 1014 M☉) in pairs of narrow-band filters selected to get continuum subtracted rest-frame Hα images for each galaxy. The excellent data allows us to detect Hα down to the 10-18 ergs/s/cm2/arcsec2 level. Here, we examine the role played by halo mass and galaxy stellar mass in deciding the overall star formation activity in star forming disks by comparing stacked Hα profiles of galaxies in different halo mass and stellar mass bins. With this preliminary study, we have found that the star-formation activity in star-forming galaxies decreases in larger halos compared to the field galaxies. Using median equivalent width profiles,...

Research paper thumbnail of Triple Bars and Complex Central Structures in Disk Galaxies

The Astrophysical Journal, 1999

We present an analysis of ground-based and HST images of three early-type barred galaxies. The fi... more We present an analysis of ground-based and HST images of three early-type barred galaxies. The first, NGC 2681, may be the clearest example yet of a galaxy with three concentric bars. The two other galaxies were previously suggested as triple-barred. Our analysis shows that while NGC 3945 is probably double-barred, NGC 4371 has only one bar; but both have intriguing central structures. NGC 3945 has a large, extremely bright disk inside its primary bar, with patchy dust lanes, a faint nuclear ring or pseudo-ring within the disk, and an apparent secondary bar crossing the ring. NGC 4371 has a bright nuclear ring only marginally bluer than the surrounding bulge and bar. There is no evidence for significant dust or star formation in either of these nuclear rings. The presence of stellar nuclear rings suggests that the centers of these galaxies are dynamically cool and disklike.

Research paper thumbnail of Optical and near IR galaxy number counts in the GOYA survey. The ages of Ellipticals

Based on the GOYA Photometric Survey of the HST Groth-Westphal strip, we present galaxy number co... more Based on the GOYA Photometric Survey of the HST Groth-Westphal strip, we present galaxy number counts in B and Ks bands together with a model that simultaneously reproduces the counts and that does not need to add an extra population of blue dwarf galaxies to reproduce the blue excess of the counts at faint magnitudes.

Research paper thumbnail of Colors of intermediate z bulges in the GOYA survey

The chronology of bulge and disk formation is a major unsolved issue in galaxy formation, which i... more The chronology of bulge and disk formation is a major unsolved issue in galaxy formation, which impacts on our global understanding of the Hubble sequence. We present colors of the nuclear regions of intermediate-redshift disk galaxies, with the aim of obtaining empirical information of ages of bulges at 0.1 < z < 1.3.

Research paper thumbnail of The central bulges of galaxies at 0.3 < z < 1.0

We have studied the colors of the bulge component of 133 galaxies from the HST Groth Strip Survey... more We have studied the colors of the bulge component of 133 galaxies from the HST Groth Strip Survey (Groth et al. 1994), covering redshifts 0.3 < z 1.4'', and inclination above 50 degrees in order to avoid reddening from dust in the disk on one side of the bulges. We find that, as in the Local Universe, the minor axis

Research paper thumbnail of What Can the Radial Surface Brightness Profiles of Galaxy Discs Tell Us About Their Evolution?

Galaxies and their Masks, 2010

Page 1. What Can the Radial Surface Brightness Profiles of Galaxy Discs Tell Us About Their Evolu... more Page 1. What Can the Radial Surface Brightness Profiles of Galaxy Discs Tell Us About Their Evolution? John E. Beckman, Leonel Gutiérrez, Peter Erwin, Ruyman Azzollini, and Inma Martínez-Valpuesta Abstract Deriving the ...

Research paper thumbnail of Pseudobulges in Barred S0 Galaxies

Astrophysics and Space Science Library, 2004

We present preliminary results from an ongoing study of the bulges of S0 galaxies. We show that i... more We present preliminary results from an ongoing study of the bulges of S0 galaxies. We show that in a subsample of 14 barred S0 galaxies, fully half the photometrically defined bulges show kinematic signatures of pseudobulges -that is, their kinematics are dominated by rotation. In four of these galaxies, we identify at least two subcomponents in the photometric bulge region: flatter, disk or bar components, assocated with disklike kinematics, and rounder "inner bulges," which appear to be hotter systems more like classical bulges.

Research paper thumbnail of Strong Fe II forbidden line emission from NGC 1275

The Astrophysical Journal, 1993

Research paper thumbnail of The Coexistence of Classical Bulges, Pseudo-bulges, and Supermassive Black Holes

Some S0 and early-type spiral galaxies possess "composite bulges"; in these galaxies, the photome... more Some S0 and early-type spiral galaxies possess "composite bulges"; in these galaxies, the photometric bulge -the central stellar light in excess of the disk light -is composed of both a "(disky) pseudobulge", with a flattened, disklike morphology and relatively cool stellar kinematics, and a rounder, kinematically hot "classical bulge" embedded within. I speculate that supermassive black holes in such galaxies may correlate with the classical-bulge component only, and not with the pseudobulge component; preliminary comparisons with SMBH masses appear to support this hypothesis.

Research paper thumbnail of NGC 4340: Double Bar + Fossil Nuclear Ring

The Evolution of Galaxies, 2001

Research paper thumbnail of Photometry of bulges at intermediate z (Dominguez-Palmero+, 2008)

Analysis of bulges to redshifts of up to z=1 have provided ambiguous results as to whether bulges... more Analysis of bulges to redshifts of up to z=1 have provided ambiguous results as to whether bulges as a class are old structures akin to elliptical galaxies or younger products of the evolution of their host disks. We aim to define a sample of intermediate-z disk galaxies harbouring central bulges, and a complementary sample of disk galaxies without measurable bulges.

Research paper thumbnail of GOYA Survey: Mergers up to z = 1 in B and Ks-selected samples

In this work we present merger fractions from galaxy samples selected by either Ks-luminosity, or... more In this work we present merger fractions from galaxy samples selected by either Ks-luminosity, or B-band luminosity, from the GOYA photometric survey of the Groth strip using asymmetry indices to identify merging galaxies. The merger fraction in B-band can be approximated by the function F_{mg}(z) = 0.006(1 + z)^{3.2}. The merger fraction in Ks-band has a minimum at z =

Research paper thumbnail of Barred Galaxies in the Coma Cluster

We use ACS data from the HST Treasury survey of the Coma cluster (z˜0.02) to study the properties... more We use ACS data from the HST Treasury survey of the Coma cluster (z˜0.02) to study the properties of barred galaxies in the Coma core, the densest environment in the nearby Universe. This study provides a complementary data point for studies of barred galaxies as a function of redshift and environment. From ˜470 cluster members brighter than MI = -11 mag, we select a sample of 46 disk galaxies (S0-Im) based on visual classification. The sample is dominated by S0s for which we find an optical bar fraction of 47±11% through ellipse fitting and visual inspection. Among the bars in the core of the Coma cluster, we do not find any very large (abar>2 kpc) bars. Comparison to other studies reveals that while the optical bar fraction for S0s shows only a modest variation across low-to-intermediate density environments (field to intermediate-density clusters), it can be higher by up to a factor of ˜ 2 in the very high-density environment of the rich Coma cluster core.

Research paper thumbnail of The 1.0-1.3 micron spectrum of LkH-alpha 101

The Astrophysical Journal, 1991

Research paper thumbnail of GOYA Survey: U and B Number Counts in the Groth‐Westphal Strip

The Astrophysical Journal, 2006

We present U and B galaxy differential number counts from a field of ∼900 arcmin 2 , based on GOY... more We present U and B galaxy differential number counts from a field of ∼900 arcmin 2 , based on GOYA Survey imaging of the HST Groth-Westphal strip. Source detection efficiency corrections as a function of the object size have been applied. A variation of the half-exposure image method has been devised to identify and remove spurious detections. Achieved 50% detection efficiencies are 24.8 mag in U and 25.5 mag in B in the Vega system. Number count slopes are d log(N )/dm = 0.50 ± 0.02 for B=21.0-24.5, and d log(N )/dm = 0.48 ± 0.03 for U =21.0-24.0. Simple number count models are presented that simultaneously reproduce the counts over 15 mag in U and B, and over 10 mag in K s , using a Λ-dominated cosmology and SDSS local luminosity functions. Only by setting a recent z f ∼ 1.5 formation redshift for early-type, red galaxies do the models reproduce the change of slope observed at K s = 17.5 in NIR counts. A moderate optical depth (τ B = 0.6) for all galaxy types ensures that the recent formation for ellipticals does not leave a signature in the U or B number counts, which are featureless at intermediate magnitudes. No ad-hoc disappearing populations are needed to explain the counts if number evolution is introduced using an observationally-based z-evolution of the merger fraction.

Research paper thumbnail of ROBUST DETERMINATION OF THE MAJOR MERGER FRACTION AT Z = 0.6 IN THE GROTH STRIP

The Astrophysical Journal, 2009

We measure the fraction of galaxies undergoing disk-disk major mergers (f mph m ) at intermediate... more We measure the fraction of galaxies undergoing disk-disk major mergers (f mph m ) at intermediate redshifts (0.35 ≤ z < 0.85) by studying the asymmetry index A of galaxy images. Results are provided for B-and K s -band absolute magnitude selected samples from the Groth strip in the GOYA photometric survey. Three sources of systematic error are carefully addressed and quantified. The effects of the large errors in the photometric redshifts and asymmetry indices are corrected with maximum likelihood techniques. Biases linked to the redshift degradation of the morphological information in the images are treated by measuring asymmetries on images artificially redshifted to a reference redshift of z d = 0.75. Morphological K-corrections are further constrained by staying within redshifts where the images sample redward of 4000Å. We find: (i) our data allow for a robust merger fraction to be provided for a single redshift bin, which we center at z = 0.6. (ii) Merger fractions at that z have lower values than previous determinations: f mph m = 0.045 +0.014 −0.011 for M B ≤ −20 galaxies, and f mph m = 0.031 +0.013 −0.009 for M Ks ≤ −23.5 galaxies. And, (iii) failure to address the effects of the large observational errors leads to overestimating f mph m by factors of 10%-60%. Combining our results with those on other B-band selected samples, and parameterizing the merger fraction evolution as f mph m (z) = f mph m (1 + z) m , we obtain that m = 2.9 ± 0.8, and f mph m (0) = 0.012 ± 0.004. For an assumed merger time-scale between 0.35-0.6 Gyr, these values imply that only 20%-35% of present day M B ≤ −20 galaxies have undergone a disk-disk major merger since z ∼ 1 Assuming a K s -band mass-to-light ratio not varying with luminosity, we infer that the merger rate of galaxies with stellar mass M ⋆ 3.5 × 10 10 M ⊙ is ℜ m = 1.6 +0.9 −0.6 × 10 −4 Mpc −3 Gyr −1 at z = 0.6. When we compare with previous studies at similar redshifts, we find that the merger rate decreases when mass increases.

Research paper thumbnail of Near-infrared forbidden Fe II emission of M82 supernova remnants - Implications for tracing the supernova content of galaxies

The Astrophysical Journal, 1991

... NEAR-INFRARED [Fe ii] EMISSION OF M82 SUPERNOVA REMNANTS: IMPLICATIONS FOR TRACING THE SUPERN... more ... NEAR-INFRARED [Fe ii] EMISSION OF M82 SUPERNOVA REMNANTS: IMPLICATIONS FOR TRACING THE SUPERNOVA CONTENT OF GALAXIES MATTHEW A. GREENHOUSE ... of maximum ion concentration of colIisi ionized Fe is 1.6 x i€YK (Shuli &amp;amp; Van Steenberg 1 982). ...

Research paper thumbnail of Vertical Instabilities and Off‐Plane Orbits in Circumbinary Disks

The Astrophysical Journal, 1999

Research paper thumbnail of When Is a Bulge Not a Bulge? Inner Disks Masquerading as Bulges in NGC 2787 and NGC 3945

The Astrophysical Journal, 2003

We present a detailed morphological, photometric, and kinematic analysis of two barred S0 galaxie... more We present a detailed morphological, photometric, and kinematic analysis of two barred S0 galaxies with large, luminous inner disks inside their bars. We show that these structures, in addition to being geometrically disk-like, have exponential profiles (scale lengths ∼ 300-500 pc) distinct from the central, non-exponential bulges. We also find them to be kinematically disk-like. The inner disk in NGC 2787 has a luminosity roughly twice that of the bulge; but in NGC 3945, the inner disk is almost ten times more luminous than the bulge, which itself is extremely small (half-light radius ≈ 100 pc, in a galaxy with an outer ring of radius ≈ 14 kpc) and only ∼ 5% of the total luminosity -a bulge/total ratio much more typical of an Sc galaxy. We estimate that at least 20% of (barred) S0 galaxies may have similar structures, which means that their bulge/disk ratios may be significantly overestimated. These inner disks dominate the central light of their galaxies; they are at least an order of magnitude larger than typical "nuclear disks" found in ellipticals and early-type spirals. Consequently, they must affect the dynamics of the bars in which they reside.

Research paper thumbnail of A Correlation between Galaxy Light Concentration and Supermassive Black Hole Mass

The Astrophysical Journal, 2001

We present evidence for a strong correlation between the concentration of bulges and the mass of ... more We present evidence for a strong correlation between the concentration of bulges and the mass of their central supermassive black hole (M bh ) -more concentrated bulges have more massive black holes. Using C re (1/3) from Trujillo, Graham, & Caon (2001b) as a measure of bulge concentration, we find that log(M bh /M ⊙ ) = 6.81(±0.95)C re (1/3) + 5.03 ± 0.41. This correlation is shown to be marginally stronger (Spearman's r s = 0.91) than the relationship between the logarithm of the stellar velocity dispersion and log M bh (Spearman's r s = 0.86), and has comparable, or less, scatter (0.31 dex in log M bh , which decreases to 0.19 dex when we use only those galaxies whose supermassive black hole's radius of influence is resolved and remove one well understood outlying data point). It would appear that the central black hole mass can be estimated from surface photometry alone, without the expensive addition of velocity dispersion determinations.

Research paper thumbnail of Hα Surface Brightness Profiles of Star-Forming Galaxies and Dependence on Halo Mass Using the HAGGIS Survey

We present the first results from the Hα Galaxy Groups Imaging Survey (HAGGIS), a narrow-band ima... more We present the first results from the Hα Galaxy Groups Imaging Survey (HAGGIS), a narrow-band imaging survey of SDSS groups at z < 0.05 conducted using the Wide Field Imager (WFI) on the ESO/MPG 2.2-meter telescope and the Wide Field Camera (WFC) on the Issac Newton Telescope (INT). In total, we observed 100 galaxy groups with a wide range of halo mass (1012 - 1014 M☉) in pairs of narrow-band filters selected to get continuum subtracted rest-frame Hα images for each galaxy. The excellent data allows us to detect Hα down to the 10-18 ergs/s/cm2/arcsec2 level. Here, we examine the role played by halo mass and galaxy stellar mass in deciding the overall star formation activity in star forming disks by comparing stacked Hα profiles of galaxies in different halo mass and stellar mass bins. With this preliminary study, we have found that the star-formation activity in star-forming galaxies decreases in larger halos compared to the field galaxies. Using median equivalent width profiles,...

Research paper thumbnail of Triple Bars and Complex Central Structures in Disk Galaxies

The Astrophysical Journal, 1999

We present an analysis of ground-based and HST images of three early-type barred galaxies. The fi... more We present an analysis of ground-based and HST images of three early-type barred galaxies. The first, NGC 2681, may be the clearest example yet of a galaxy with three concentric bars. The two other galaxies were previously suggested as triple-barred. Our analysis shows that while NGC 3945 is probably double-barred, NGC 4371 has only one bar; but both have intriguing central structures. NGC 3945 has a large, extremely bright disk inside its primary bar, with patchy dust lanes, a faint nuclear ring or pseudo-ring within the disk, and an apparent secondary bar crossing the ring. NGC 4371 has a bright nuclear ring only marginally bluer than the surrounding bulge and bar. There is no evidence for significant dust or star formation in either of these nuclear rings. The presence of stellar nuclear rings suggests that the centers of these galaxies are dynamically cool and disklike.

Research paper thumbnail of Optical and near IR galaxy number counts in the GOYA survey. The ages of Ellipticals

Based on the GOYA Photometric Survey of the HST Groth-Westphal strip, we present galaxy number co... more Based on the GOYA Photometric Survey of the HST Groth-Westphal strip, we present galaxy number counts in B and Ks bands together with a model that simultaneously reproduces the counts and that does not need to add an extra population of blue dwarf galaxies to reproduce the blue excess of the counts at faint magnitudes.

Research paper thumbnail of Colors of intermediate z bulges in the GOYA survey

The chronology of bulge and disk formation is a major unsolved issue in galaxy formation, which i... more The chronology of bulge and disk formation is a major unsolved issue in galaxy formation, which impacts on our global understanding of the Hubble sequence. We present colors of the nuclear regions of intermediate-redshift disk galaxies, with the aim of obtaining empirical information of ages of bulges at 0.1 < z < 1.3.

Research paper thumbnail of The central bulges of galaxies at 0.3 < z < 1.0

We have studied the colors of the bulge component of 133 galaxies from the HST Groth Strip Survey... more We have studied the colors of the bulge component of 133 galaxies from the HST Groth Strip Survey (Groth et al. 1994), covering redshifts 0.3 < z 1.4'', and inclination above 50 degrees in order to avoid reddening from dust in the disk on one side of the bulges. We find that, as in the Local Universe, the minor axis

Research paper thumbnail of What Can the Radial Surface Brightness Profiles of Galaxy Discs Tell Us About Their Evolution?

Galaxies and their Masks, 2010

Page 1. What Can the Radial Surface Brightness Profiles of Galaxy Discs Tell Us About Their Evolu... more Page 1. What Can the Radial Surface Brightness Profiles of Galaxy Discs Tell Us About Their Evolution? John E. Beckman, Leonel Gutiérrez, Peter Erwin, Ruyman Azzollini, and Inma Martínez-Valpuesta Abstract Deriving the ...

Research paper thumbnail of Pseudobulges in Barred S0 Galaxies

Astrophysics and Space Science Library, 2004

We present preliminary results from an ongoing study of the bulges of S0 galaxies. We show that i... more We present preliminary results from an ongoing study of the bulges of S0 galaxies. We show that in a subsample of 14 barred S0 galaxies, fully half the photometrically defined bulges show kinematic signatures of pseudobulges -that is, their kinematics are dominated by rotation. In four of these galaxies, we identify at least two subcomponents in the photometric bulge region: flatter, disk or bar components, assocated with disklike kinematics, and rounder "inner bulges," which appear to be hotter systems more like classical bulges.

Research paper thumbnail of Strong Fe II forbidden line emission from NGC 1275

The Astrophysical Journal, 1993

Research paper thumbnail of The Coexistence of Classical Bulges, Pseudo-bulges, and Supermassive Black Holes

Some S0 and early-type spiral galaxies possess "composite bulges"; in these galaxies, the photome... more Some S0 and early-type spiral galaxies possess "composite bulges"; in these galaxies, the photometric bulge -the central stellar light in excess of the disk light -is composed of both a "(disky) pseudobulge", with a flattened, disklike morphology and relatively cool stellar kinematics, and a rounder, kinematically hot "classical bulge" embedded within. I speculate that supermassive black holes in such galaxies may correlate with the classical-bulge component only, and not with the pseudobulge component; preliminary comparisons with SMBH masses appear to support this hypothesis.

Research paper thumbnail of NGC 4340: Double Bar + Fossil Nuclear Ring

The Evolution of Galaxies, 2001

Research paper thumbnail of Photometry of bulges at intermediate z (Dominguez-Palmero+, 2008)

Analysis of bulges to redshifts of up to z=1 have provided ambiguous results as to whether bulges... more Analysis of bulges to redshifts of up to z=1 have provided ambiguous results as to whether bulges as a class are old structures akin to elliptical galaxies or younger products of the evolution of their host disks. We aim to define a sample of intermediate-z disk galaxies harbouring central bulges, and a complementary sample of disk galaxies without measurable bulges.

Research paper thumbnail of GOYA Survey: Mergers up to z = 1 in B and Ks-selected samples

In this work we present merger fractions from galaxy samples selected by either Ks-luminosity, or... more In this work we present merger fractions from galaxy samples selected by either Ks-luminosity, or B-band luminosity, from the GOYA photometric survey of the Groth strip using asymmetry indices to identify merging galaxies. The merger fraction in B-band can be approximated by the function F_{mg}(z) = 0.006(1 + z)^{3.2}. The merger fraction in Ks-band has a minimum at z =

Research paper thumbnail of Barred Galaxies in the Coma Cluster

We use ACS data from the HST Treasury survey of the Coma cluster (z˜0.02) to study the properties... more We use ACS data from the HST Treasury survey of the Coma cluster (z˜0.02) to study the properties of barred galaxies in the Coma core, the densest environment in the nearby Universe. This study provides a complementary data point for studies of barred galaxies as a function of redshift and environment. From ˜470 cluster members brighter than MI = -11 mag, we select a sample of 46 disk galaxies (S0-Im) based on visual classification. The sample is dominated by S0s for which we find an optical bar fraction of 47±11% through ellipse fitting and visual inspection. Among the bars in the core of the Coma cluster, we do not find any very large (abar>2 kpc) bars. Comparison to other studies reveals that while the optical bar fraction for S0s shows only a modest variation across low-to-intermediate density environments (field to intermediate-density clusters), it can be higher by up to a factor of ˜ 2 in the very high-density environment of the rich Coma cluster core.

Research paper thumbnail of The 1.0-1.3 micron spectrum of LkH-alpha 101

The Astrophysical Journal, 1991

Research paper thumbnail of GOYA Survey: U and B Number Counts in the Groth‐Westphal Strip

The Astrophysical Journal, 2006

We present U and B galaxy differential number counts from a field of ∼900 arcmin 2 , based on GOY... more We present U and B galaxy differential number counts from a field of ∼900 arcmin 2 , based on GOYA Survey imaging of the HST Groth-Westphal strip. Source detection efficiency corrections as a function of the object size have been applied. A variation of the half-exposure image method has been devised to identify and remove spurious detections. Achieved 50% detection efficiencies are 24.8 mag in U and 25.5 mag in B in the Vega system. Number count slopes are d log(N )/dm = 0.50 ± 0.02 for B=21.0-24.5, and d log(N )/dm = 0.48 ± 0.03 for U =21.0-24.0. Simple number count models are presented that simultaneously reproduce the counts over 15 mag in U and B, and over 10 mag in K s , using a Λ-dominated cosmology and SDSS local luminosity functions. Only by setting a recent z f ∼ 1.5 formation redshift for early-type, red galaxies do the models reproduce the change of slope observed at K s = 17.5 in NIR counts. A moderate optical depth (τ B = 0.6) for all galaxy types ensures that the recent formation for ellipticals does not leave a signature in the U or B number counts, which are featureless at intermediate magnitudes. No ad-hoc disappearing populations are needed to explain the counts if number evolution is introduced using an observationally-based z-evolution of the merger fraction.

Research paper thumbnail of ROBUST DETERMINATION OF THE MAJOR MERGER FRACTION AT Z = 0.6 IN THE GROTH STRIP

The Astrophysical Journal, 2009

We measure the fraction of galaxies undergoing disk-disk major mergers (f mph m ) at intermediate... more We measure the fraction of galaxies undergoing disk-disk major mergers (f mph m ) at intermediate redshifts (0.35 ≤ z < 0.85) by studying the asymmetry index A of galaxy images. Results are provided for B-and K s -band absolute magnitude selected samples from the Groth strip in the GOYA photometric survey. Three sources of systematic error are carefully addressed and quantified. The effects of the large errors in the photometric redshifts and asymmetry indices are corrected with maximum likelihood techniques. Biases linked to the redshift degradation of the morphological information in the images are treated by measuring asymmetries on images artificially redshifted to a reference redshift of z d = 0.75. Morphological K-corrections are further constrained by staying within redshifts where the images sample redward of 4000Å. We find: (i) our data allow for a robust merger fraction to be provided for a single redshift bin, which we center at z = 0.6. (ii) Merger fractions at that z have lower values than previous determinations: f mph m = 0.045 +0.014 −0.011 for M B ≤ −20 galaxies, and f mph m = 0.031 +0.013 −0.009 for M Ks ≤ −23.5 galaxies. And, (iii) failure to address the effects of the large observational errors leads to overestimating f mph m by factors of 10%-60%. Combining our results with those on other B-band selected samples, and parameterizing the merger fraction evolution as f mph m (z) = f mph m (1 + z) m , we obtain that m = 2.9 ± 0.8, and f mph m (0) = 0.012 ± 0.004. For an assumed merger time-scale between 0.35-0.6 Gyr, these values imply that only 20%-35% of present day M B ≤ −20 galaxies have undergone a disk-disk major merger since z ∼ 1 Assuming a K s -band mass-to-light ratio not varying with luminosity, we infer that the merger rate of galaxies with stellar mass M ⋆ 3.5 × 10 10 M ⊙ is ℜ m = 1.6 +0.9 −0.6 × 10 −4 Mpc −3 Gyr −1 at z = 0.6. When we compare with previous studies at similar redshifts, we find that the merger rate decreases when mass increases.

Research paper thumbnail of Near-infrared forbidden Fe II emission of M82 supernova remnants - Implications for tracing the supernova content of galaxies

The Astrophysical Journal, 1991

... NEAR-INFRARED [Fe ii] EMISSION OF M82 SUPERNOVA REMNANTS: IMPLICATIONS FOR TRACING THE SUPERN... more ... NEAR-INFRARED [Fe ii] EMISSION OF M82 SUPERNOVA REMNANTS: IMPLICATIONS FOR TRACING THE SUPERNOVA CONTENT OF GALAXIES MATTHEW A. GREENHOUSE ... of maximum ion concentration of colIisi ionized Fe is 1.6 x i€YK (Shuli &amp;amp; Van Steenberg 1 982). ...

Research paper thumbnail of Vertical Instabilities and Off‐Plane Orbits in Circumbinary Disks

The Astrophysical Journal, 1999

Research paper thumbnail of When Is a Bulge Not a Bulge? Inner Disks Masquerading as Bulges in NGC 2787 and NGC 3945

The Astrophysical Journal, 2003

We present a detailed morphological, photometric, and kinematic analysis of two barred S0 galaxie... more We present a detailed morphological, photometric, and kinematic analysis of two barred S0 galaxies with large, luminous inner disks inside their bars. We show that these structures, in addition to being geometrically disk-like, have exponential profiles (scale lengths ∼ 300-500 pc) distinct from the central, non-exponential bulges. We also find them to be kinematically disk-like. The inner disk in NGC 2787 has a luminosity roughly twice that of the bulge; but in NGC 3945, the inner disk is almost ten times more luminous than the bulge, which itself is extremely small (half-light radius ≈ 100 pc, in a galaxy with an outer ring of radius ≈ 14 kpc) and only ∼ 5% of the total luminosity -a bulge/total ratio much more typical of an Sc galaxy. We estimate that at least 20% of (barred) S0 galaxies may have similar structures, which means that their bulge/disk ratios may be significantly overestimated. These inner disks dominate the central light of their galaxies; they are at least an order of magnitude larger than typical "nuclear disks" found in ellipticals and early-type spirals. Consequently, they must affect the dynamics of the bars in which they reside.

Research paper thumbnail of A Correlation between Galaxy Light Concentration and Supermassive Black Hole Mass

The Astrophysical Journal, 2001

We present evidence for a strong correlation between the concentration of bulges and the mass of ... more We present evidence for a strong correlation between the concentration of bulges and the mass of their central supermassive black hole (M bh ) -more concentrated bulges have more massive black holes. Using C re (1/3) from Trujillo, Graham, & Caon (2001b) as a measure of bulge concentration, we find that log(M bh /M ⊙ ) = 6.81(±0.95)C re (1/3) + 5.03 ± 0.41. This correlation is shown to be marginally stronger (Spearman's r s = 0.91) than the relationship between the logarithm of the stellar velocity dispersion and log M bh (Spearman's r s = 0.86), and has comparable, or less, scatter (0.31 dex in log M bh , which decreases to 0.19 dex when we use only those galaxies whose supermassive black hole's radius of influence is resolved and remove one well understood outlying data point). It would appear that the central black hole mass can be estimated from surface photometry alone, without the expensive addition of velocity dispersion determinations.