arXiv subjects

Paul Martini

Publications and source records attributed to Paul Martini.

At least 127 records · Page 7Linked to original sources

arXiv2014

KOSMOS and COSMOS: New facility instruments for the NOAO 4-meter telescopes

We describe the design, construction and measured performance of the Kitt Peak Ohio State Multi-Object Spectrograph (KOSMOS) for the 4-m Mayall telescope and the Cerro Tololo Ohio State Multi-Object Spectrograph (COSMOS) for the 4-m Blanco telescope. These nearly identical imaging spectrographs are modified versions of the OSMOS instrument; they provide a pair of new, high-efficiency instruments to the NOAO user community. KOSMOS and COSMOS may be used for imaging, long-slit, and multi-slit spectroscopy over a 100 square arcminute field of view with a pixel scale of 0.29 arcseconds. Each contains two VPH grisms that provide R~2500 with a one arcsecond slit and their wavelengths of peak diffraction efficiency are approximately 510nm and 750nm. Both may also be used with either a thin, blue-optimized CCD from e2v or a thick, fully depleted, red-optimized CCD from LBNL. These instruments were developed in response to the ReSTAR process. KOSMOS was commissioned in 2013B and COSMOS was commissioned in 2014A.

astro-ph.IM↗

arXiv2013

Dust Scattering and the Radiation Pressure Force in the M82 Superwind

Radiation pressure on dust grains may be an important physical mechanism driving galaxy-wide superwinds in rapidly star-forming galaxies. We calculate the combined dust and gas Eddington ratio (Gamma) for the archetypal superwind of M82. By combining archival GALEX data, a standard dust model, Monte Carlo dust scattering calculations, and the Herschel map of the dust surface density distribution, the observed FUV/NUV surface brightness in the outflow constrains both the total UV luminosity escaping from the starburst along its minor axis (L_*, UV) and the flux-mean opacity, thus allowing a calculation of Gamma. We find that L_(*, UV) ~ 1-6*10^42 ergs s^-1, ~2-12 times greater than the UV luminosity observed from our line of sight. On a scale of 1-3 kpc above the plane of M82, we find that Gamma ~ 0.01 - 0.06. On smaller scales (~0.25-0.5 kpc), where the enclosed mass decreases, our calculation of L_(*, UV) implies that Gamma ~ 0.1 with factor of few uncertainties. Within the starburst itself, we estimate the single-scattering Eddington ratio to be of order unity. Thus, although radiation pressure is weak compared to gravity on kpc scales above the plane of M82, it may yet be important in launching the observed outflow. We discuss the primary uncertainties in our calculation, the sensitivity of Gamma to the dust grain size distribution, and the time evolution of the wind following M82's recent starburst episodes.

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arXiv2013

Discovery of a Large Population of Ultraluminous X-ray Sources in the Bulge-less Galaxies NGC 337 and ESO 501-23

We have used Chandra observations of eight bulge-less disk galaxies to identify new ultraluminous X-ray source (ULX) candidates, study their high mass X-ray binary (HMXB) population, and search for low-luminosity active galactic nuclei (AGN). We report the discovery of 16 new ULX candidates in our sample of galaxies. Eight of these are found in the star forming galaxy NGC 337, none of which are expected to be background contaminants. The HMXB luminosity function of NGC 337 implies a star formation rate (SFR) of 6.8$^{+4.4}_{-3.5}$ \msun\ yr$^{-1}$, consistent at 1.5$σ$ with a recent state of the art SFR determination. We also report the discovery of a bright ULX candidate (X-1) in ESO 501-23. X-1's spectrum is well fit by an absorbed power law with $Γ= 1.18^{+0.19}_{-0.11}$ and N$\rm{_H}$ = 1.13$^{+7.07}_{-1.13} \times 10^{20}$ cm$^{-2}$, implying a 0.3-8 keV flux of $1.08^{+0.05}_{-0.07} \times 10^{-12}$ \esc. Its X-ray luminosity (L$_X$) is poorly constrained due to uncertainties in the host galaxy's distance, but we argue that its spectrum implies L$_X > 10^{40}$ \es. An optical counterpart to this object may be present in HST imaging. We also identify ULX candidates in IC 1291, PGC 3853, NGC 5964 and NGC 2805. We find no evidence of nuclear activity in the galaxies in our sample, placing a flux upper limit of $4 \times 10^{-15}$ \esc\ on putative AGN. Additionally, the type II-P supernova SN 2011DQ in NGC 337, which exploded 2 months before our X-ray observation, is undetected.

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arXiv2013

The Cluster and Field Galaxy AGN Fraction at z = 1 to 1.5: Evidence for a Reversal of the Local Anticorrelation Between Environment and AGN Fraction

The fraction of cluster galaxies that host luminous AGN is an important probe of AGN fueling processes, the cold ISM at the centers of galaxies, and how tightly black holes and galaxies co-evolve. We present a new measurement of the AGN fraction in a sample of 13 clusters of galaxies (M >= 10^{14} Msun) at 1 = 10^{44} erg/s. This fraction is measured relative to all cluster galaxies more luminous than M*_{3.6}(z)+1, where M*_{3.6}(z) is the absolute magnitude of the break in the galaxy luminosity function at the cluster redshift in the IRAC 3.6um bandpass. The cluster AGN fraction is 30 times greater than the 3sigma upper limit on the value for AGN of similar luminosity at z~0.25, as well as more than an order of magnitude greater than the AGN fraction at z~0.75. AGN with L_{X,H} >= 10^{43} erg/s exhibit similarly pronounced evolution with redshift. In contrast with the local universe, where the luminous AGN fraction is higher in the field than in clusters, the X-ray and MIR-selected AGN fractions in the field and clusters are consistent at 1<z<1.5. This is evidence that the cluster AGN population has evolved more rapidly than the field population from z~1.5 to the present. This environment-dependent AGN evolution mimics the more rapid evolution of star-forming galaxies in clusters relative to the field.

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arXiv2013

The Origin of Dust in Early-Type Galaxies and Implications for Accretion onto Supermassive Black Holes

We have conducted an archival Spitzer study of 38 early-type galaxies (ETGs) in order to determine the origin of the dust in approximately half of this population. Our sample galaxies generally have good wavelength coverage from 3.6um to 160um, as well as visible-wavelength HST images. We use the Spitzer data to estimate dust masses, or establish upper limits, and find that all of the ETGs with dust lanes in the HST data are detected in all of the Spitzer bands and have dust masses of ~10^{5-6.5} Msun, while galaxies without dust lanes are not detected at 70um and 160um and typically have <10^5 Msun of dust. The apparently dust-free galaxies do have 24um emission that scales with the shorter wavelength flux, yet substantially exceeds the expectations of photospheric emission by approximately a factor of three. We conclude this emission is dominated by hot, circumstellar dust around evolved stars that does not survive to form a substantial interstellar component. The order of magnitude variations in dust masses between galaxies with similar stellar populations rules out a subtantial contribution from continual, internal production in spite of the clear evidence for circumstellar dust. We demonstrate that the interstellar dust is not due to purely external accretion, unless the product of the merger rate of dusty satellites and the dust lifetime is at least an order of magnitude higher than expected. We propose that dust in ETGs is seeded by external accretion, yet the accreted dust is maintained by continued growth in externally-accreted cold gas beyond the nominal lifetime of individual grains. The several Gyr depletion time of the cold gas is long enough to reconcile the fraction of dusty ETGs with the merger rate of gas-rich satellites. As the majority of dusty ETGs are also low-luminosity AGN and likely fueled by this cold gas, their lifetime should similarly be several Gyr.

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arXiv2013

The Mass-Metallicity Relation with the Direct Method on Stacked Spectra of SDSS Galaxies

The relation between galaxy stellar mass and gas-phase metallicity is a sensitive diagnostic of the main processes that drive galaxy evolution, namely cosmological gas inflow, metal production in stars, and gas outflow via galactic winds. We employed the direct method to measure the metallicities of ~200,000 star-forming galaxies from the SDSS that were stacked in bins of (1) stellar mass and (2) both stellar mass and star formation rate (SFR) to significantly enhance the signal-to-noise ratio of the weak [O III] 4363 and [O II] 7320, 7330 auroral lines required to apply the direct method. These metallicity measurements span three decades in stellar mass from log(Mstar/Msun) = 7.4-10.5, which allows the direct method mass-metallicity relation to simultaneously capture the high-mass turnover and extend a full decade lower in mass than previous studies that employed more uncertain strong line methods. The direct method mass-metallicity relation rises steeply at low mass (O/H ~ Mstar^{1/2}) until it turns over at log(Mstar/Msun) = 8.9 and asymptotes to 12 + log(O/H) = 8.8 at high mass. The direct method mass-metallicity relation has a steeper slope, a lower turnover mass, and a factor of two to three greater dependence on SFR than strong line mass-metallicity relations. Furthermore, the SFR-dependence appears monotonic with stellar mass, unlike strong line mass-metallicity relations. We also measure the N/O abundance ratio, an important tracer of star formation history, and find the clear signature of primary and secondary nitrogen enrichment. N/O correlates tightly with oxygen abundance, and even more so with stellar mass.

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arXiv2012

The Structure of the Broad Line Region in AGN: I. Reconstructed Velocity-Delay Maps

We present velocity-resolved reverberation results for five active galactic nuclei. We recovered velocity-delay maps using the maximum-entropy method for four objects: Mrk 335, Mrk 1501, 3C120, and PG2130+099. For the fifth, Mrk 6, we were only able to measure mean time delays in different velocity bins of the Hbeta emission line. The four velocity-delay maps show unique dynamical signatures for each object. For 3C120, the Balmer lines show kinematic signatures consistent with both an inclined disk and infalling gas, but the HeII 4686 emission line is suggestive only of inflow. The Balmer lines in Mrk 335, Mrk 1501, and PG 2130+099 show signs of infalling gas, but the HeII emission in Mrk 335 is consistent with an inclined disk. We also see tentative evidence of combined virial motion and infalling gas from the velocity-binned analysis of Mrk 6. The maps for 3C120 and Mrk 335 are two of the most clearly defined velocity-delay maps to date. These maps constitute a large increase in the number of objects for which we have resolved velocity-delay maps and provide evidence supporting the reliability of reverberation-based black hole mass measurements.

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arXiv2012

MMT & Magellan Infrared Spectrograph

The MMT and Magellan infrared spectrograph (MMIRS) is a cryogenic multiple slit spectrograph operating in the wavelength range 0.9-2.4 micron. MMIRS' refractive optics offer a 6.9 by 6.9 arcmin field of view for imaging with a spatial resolution of 0.2 arcsec per pixel on a HAWAII-2 array. For spectroscopy, MMIRS can be used with long slits up to 6.9 arcmin long, or with custom slit masks having slitlets distributed over a 4 by 6.9 arcmin area. A range of dispersers offer spectral resolutions of 800 to 3000. MMIRS is designed to be used at the f/5 foci of the MMT or Magellan Clay 6.5m telescopes. MMIRS was commissioned in 2009 at the MMT and has been in routine operation at the Magellan Clay Telescope since 2010. MMIRS is being used for a wide range of scientific investigations from exoplanet atmospheres to Ly-alpha emitters.

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arXiv2012

Addressing Decadal Survey Science through Community Access to Highly Multiplexed Spectroscopy with BigBOSS on the KPNO Mayall Telescope

This document summarizes the results of a community-based discussion of the potential science impact of the Mayall+BigBOSS highly multiplexed multi-object spectroscopic capability. The KPNO Mayall 4m telescope equipped with the DOE- and internationally-funded BigBOSS spectrograph offers one of the most cost-efficient ways of accomplishing many of the pressing scientific goals identified for this decade by the "New Worlds, New Horizons" report. The BigBOSS Key Project will place unprecedented constraints on cosmological parameters related to the expansion history of the universe. With the addition of an open (publicly funded) community access component, the scientific impact of BigBOSS can be extended to many important astrophysical questions related to the origin and evolution of galaxies, stars, and the IGM. Massive spectroscopy is the critical missing ingredient in numerous ongoing and planned ground- and space-based surveys, and BigBOSS is unique in its ability to provide this to the US community. BigBOSS data from community-led projects will play a vital role in the education and training of students and in maintaining US leadership in these fields of astrophysics. We urge the NSF-AST division to support community science with the BigBOSS multi-object spectrograph through the period of the BigBOSS survey in order to ensure public access to the extraordinary spectroscopic capability.

astro-ph.CO↗

arXiv2012

Measurement of the Mass and Stellar Population Distribution in M82 with the LBT

We present a K-band spectroscopic study of the stellar and gas kinematics, mass distribution, and stellar populations of the archetypical starburst galaxy M82. Our results are based on a single spectrum at a position angle of 67.5 degrees through the K-band nucleus. We used the CO stellar absorption band head at 2.29 μm (CO_2.29) to measure the rotation curve out to nearly 4 kpc radius on both the eastern and western sides of the galaxy. Our data show that the rotation curve is flat from 1 - 4 kpc. This stands in sharp contrast to some previous studies, which have interpreted H I and CO emission-line position-velocity diagrams as evidence for a declining rotation curve. The kinematics of the Brγ, H_2, and He I emission lines are consistent with, although characterized by slightly higher velocities than, the stellar kinematics. We derived M82's mass distribution from our stellar kinematic measurements and estimate its total dynamical mass is ~10^10 Msun. We measured the equivalent width of CO_2.29 (W_2.29) as a function of distance from the center of the galaxy to investigate the spatial extent of the red supergiant (RSG) population. The variation in W_2.29 with radius clearly shows that RSGs dominate the light inside 500 pc radius. M82's superwind is likely launched from this region, where we estimate the enclosed mass is <= 2 x 10^9 Msun.

astro-ph.CO↗

arXiv2012

The Lifetime and Powers of FR IIs in Galaxy Clusters

We have identified and studied a sample of 151 FR IIs found in brightest cluster galaxies (BCGs) in the MaxBCG cluster catalog with data from FIRST and NVSS. We have compared the radio luminosities and projected lengths of these FR IIs to the projected length distribution of a range of mock catalogs generated by an FR II model and estimate the FR II lifetime to be 1.9 x 10^8 yr. The uncertainty in the lifetime calculation is a factor of two, due primarily to uncertainties in the ICM density and the FR II axial ratio. We furthermore measure the jet power distribution of FR IIs in BCGs and find that it is well described by a log-normal distribution with a median power of 1.1 x 10^37 W and a coefficient of variation of 2.2. These jet powers are nearly linearly related to the observed luminosities, and this relation is steeper than many other estimates, although it is dependent on the jet model. We investigate correlations between FR II and cluster properties and find that galaxy luminosity is correlated with jet power. This implies that jet power is also correlated with black hole mass, as the stellar luminosity of a BCG should be a good proxy for its spheroid mass and therefore the black hole mass. Jet power, however, is not correlated with cluster richness, nor is FR II lifetime strongly correlated with any cluster properties. We calculate the enthalpy of the lobes to examine the impact of the FR IIs on the ICM and find that heating due to adiabatic expansion is too small to offset radiative cooling by a factor of at least six. In contrast, the jet power is approximately an order of magnitude larger than required to counteract cooling. We conclude that if feedback from FR IIs offsets cooling of the ICM, then heating must be primarily due to another mechanism associated with FR II expansion.

astro-ph.CO↗

arXiv2012

Reverberation Mapping Results for Five Seyfert 1 Galaxies

We present the results from a detailed analysis of photometric and spectrophotometric data on five Seyfert 1 galaxies observed as a part of a recent reverberation mapping program. The data were collected at several observatories over a 140-day span beginning in 2010 August and ending in 2011 January. We obtained high sampling-rate light curves for Mrk 335, Mrk 1501, 3C120, Mrk 6, and PG2130+099, from which we have measured the time lag between variations in the 5100 Angstrom continuum and the H-beta broad emission line. We then used these measurements to calculate the mass of the supermassive black hole at the center of each of these galaxies. Our new measurements substantially improve previous measurements of MBH and the size of the broad line-emitting region for four sources and add a measurement for one new object. Our new measurements are consistent with photoionization physics regulating the location of the broad line region in active galactic nuclei.

astro-ph.CO↗

arXiv2012

Properties of Bulgeless Disk Galaxies II. Star Formation as a Function of Circular Velocity

We study the relation between the surface density of gas and star formation rate in twenty moderately-inclined, bulgeless disk galaxies (Sd-Sdm Hubble types) using CO(1-0) data from the IRAM 30m telescope, HI emission line data from the VLA/EVLA, H-alpha data from the MDM Observatory, and PAH emission data derived from Spitzer IRAC observations. We specifically investigate the efficiency of star formation as a function of circular velocity (v_circ). Previous work found that the vertical dust structure and disk stability of edge-on, bulgeless disk galaxies transition from diffuse dust lanes with large scale heights and gravitationally-stable disks at v_circ < 120 km/s (M_star <~ 10^10 M_sun) to narrow dust lanes with small scale heights and gravitationally-unstable disks at v_circ > 120 km/s. We find no transition in star formation efficiency (Sigma_SFR/Sigma_HI+H2) at v_circ = 120 km/s, or at any other circular velocity probed by our sample (v_circ = 46 - 190 km/s). Contrary to previous work, we find no transition in disk stability at any circular velocity in our sample. Assuming our sample has the same dust structure transition as the edge-on sample, our results demonstrate that scale height differences in the cold interstellar medium of bulgeless disk galaxies do not significantly affect the molecular fraction or star formation efficiency. This may indicate that star formation is primarily affected by physical processes that act on smaller scales than the dust scale height, which lends support to local star formation models.

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arXiv2012

A Multi-Wavelength Study of Low Redshift Cluster of Galaxies II. Environmental Impact on Galaxy Growth

Galaxy clusters provide powerful laboratories for the study of galaxy evolution, particularly the origin of correlations of morphology and star formation rate (SFR) with density. We construct visible to MIR spectral energy distributions (SEDs) of cluster galaxies and use them to measure stellar masses and SFRs in eight low redshift clusters, which we examine as a function of environment. A partial correlation analysis indicates that SFR depends strongly on R/R200 (>99.9% confidence) and is independent of projected local density at fixed radius. SFR also shows no residual dependence on stellar mass. We therefore conclude that interactions with the intra-cluster medium drive the evolution of SFRs in cluster galaxies. A merged sample of galaxies from the five most complete clusters shows \propto(R/R200)^(1.3+/-0.7) for galaxies with R/R200<0.4. A decline in the fraction of SFGs toward the cluster center contributes most of this effect, but it is accompanied by a reduction in SFRs among star-forming galaxies (SFGs) near the cluster center. The increase in the fraction of SFGs toward larger R/R200 and the isolation of SFGs with reduced SFRs near the cluster center are consistent with ram pressure stripping as the mechanism to truncate star formation in galaxy clusters. We conclude that stripping drives the properties of SFGs over the range of radii we examine. We also find that galaxies near the cluster center are more massive than galaxies farther out in the cluster at ~3.5σ, which suggests that cluster galaxies experience dynamical relaxation during the course of their evolution.

astro-ph.CO↗

arXiv2012

Hot and Cold Galactic Gas in the NGC 2563 Galaxy Group

The role of environmentally induced gas stripping in driving galaxy evolution in groups remains poorly understood. Here we present extensive Chandra and Very Large Array mosaic observations of the hot and cold interstellar medium within the members of the nearby, X-ray bright NGC 2563 group, a prime target for studies of the role of gas stripping and interactions in relatively small host halos. Our observations cover nearly all group members within a projected radius of 1.15 Mpc (~1.4 R_vir) of the group center, down to a limiting X-ray luminosity and HI mass of 3e39 erg/s and 2e8 M_sun, respectively. The X-ray data are consistent with efficient ram pressure stripping of the hot gas halos of early-type galaxies near the group core, but no X-ray tails are seen and the limited statistics preclude strong conclusions. The HI results suggest moderate HI mass loss from the group members when compared to similar field galaxies. Six of the 20 HI-detected group members show HI evidence of ongoing interactions with other galaxies or with the intragroup medium. Suggestive evidence is further seen for galaxies with close neighbors in position-velocity space to show relatively low HI content, consistent with tidal removal of HI. The results thus indicate removal of both hot and cold gas from the group members via a combination of ram pressure stripping and tidal interactions. We also find that 16 of the 20 HI detections occur on one side of the group, reflecting an unusual morphological segregation whose origin remains unclear.

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arXiv2011

A Reverberation Lag for the High-Ionization Component of the Broad Line Region in the Narrow-Line Seyfert 1 Mrk 335

We present the first results from a detailed analysis of photometric and spectrophotometric data on the narrow-line Seyfert 1 galaxy Mrk 335, collected over a 120-day span in the fall of 2010. From these data we measure the lag in the He II 4686 broad emission line relative to the optical continuum to be 2.7 \pm 0.6 days and the lag in the Hβ4861 broad emission line to be 13.9 \pm 0.9 days. Combined with the line width, the He II lag yields a black hole mass, MBH = (2.6 \pm 0.8)\times 10^7 Msun. This measurement is consistent with measurements made using the Hβ4861 line, suggesting that the He II emission originates in the same region as Hβ, but at a much smaller radius. This constitutes the first robust lag measurement for a high-ionization line in a narrow-line Seyfert 1 galaxy.

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arXiv2011

Properties of Bulgeless Disk Galaxies. I. Atomic Gas

We study the neutral hydrogen properties of a sample of 20 bulgeless disk galaxies (Sd - Sdm Hubble types), an interesting class that can be used to constrain galaxy formation and evolution, especially the role of mergers versus internal processes. Our sample is composed of nearby (within 32 Mpc), moderately inclined galaxies that bracket the circular velocity of 120 km/s, which has been found to be associated with a transition in dust scale heights in edge-on, late-type disks. Here we present HI channel maps, line profiles, and integrated intensity maps. We also derive kinematic parameters, including the circular velocity, from rotation curve analyses and calculate the integrated HI flux and HI mass for each galaxy in the sample. Three of the 20 galaxies in our sample have kinematically distinct outer components with major axes that differ by 30 - 90 degrees from the main disk. These distinct outer components may be due to a recent interaction, which would be somewhat surprising because the disks do not contain bulges. We will use the data products and derived properties in subsequent investigations into star formation and secular evolution in bulgeless disks with circular velocities above and below 120 km/s.

astro-ph.CO↗

arXiv2011

A Multi-Wavelength Study of Low Redshift Clusters of Galaxies I. Comparison of X-ray and Mid-Infrared Selected AGNs

Clusters of galaxies have long been used as laboratories for the study of galaxy evolution, but despite intense, recent interest in feedback between AGNs and their hosts, the impact of environment on these relationships remains poorly constrained. We present results from a study of AGNs and their host galaxies found in low-redshift galaxy clusters. We fit model spectral energy distributions (SEDs) to the combined visible and mid-infrared (MIR) photometry of cluster members and use these model SEDs to determine stellar masses and star-formation rates (SFRs). We identify two populations of AGNs, the first based on their X-ray luminosities (X-ray AGNs) and the second based on the presence of a significant AGN component in their model SEDs (IR AGNs). We find that the two AGN populations are nearly disjoint; only 8 out of 44 AGNs are identified with both techniques. We further find that IR AGNs are hosted by galaxies with similar masses and SFRs but higher specific SFRs (sSFRs) than X-ray AGN hosts. The relationship between AGN accretion and host star-formation in cluster AGN hosts shows no significant difference compared to the relationship between field AGNs and their hosts. The projected radial distributions of both AGN populations are consistent with the distribution of other cluster members. We argue that the apparent dichotomy between X-ray and IR AGNs can be understood as a combination of differing extinction due to cold gas in the host galaxies of the two classes of AGNs and the presence of weak star-formation in X-ray AGN hosts.

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