R. Sanders - Kapteyn Astronomical Institute, Groningen, NL

R. Sanders
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Name
R. Sanders
Affiliation
Kapteyn Astronomical Institute, Groningen, NL
City
Groningen
Country
Netherlands

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Pub Categories

 
Astrophysics (21)
 
Astrophysics of Galaxies (16)
 
Cosmology and Nongalactic Astrophysics (11)
 
General Relativity and Quantum Cosmology (9)
 
High Energy Physics - Theory (4)
 
High Energy Physics - Experiment (3)
 
High Energy Physics - Phenomenology (3)
 
Physics - Instrumentation and Detectors (3)
 
Physics - Soft Condensed Matter (2)
 
Physics - History of Physics (2)
 
Nonlinear Sciences - Adaptation and Self-Organizing Systems (1)
 
Physics - Materials Science (1)
 
Solar and Stellar Astrophysics (1)
 
Physics - Physics and Society (1)

Publications Authored By R. Sanders

Using observations from the first two years of the MOSFIRE Deep Evolution Field (MOSDEF) survey, we study 13 AGN-driven outflows detected from a sample of 67 X-ray, IR and/or optically selected AGN at $z \sim 2$. The AGN in the sample have bolometric luminosities spanning $10^{44}-10^{46} \mathrm{erg s^{-1}}$, including both quasars and more common, moderate-luminosity AGN. We detect signatures of blueshifted, ionized gas outflows in the \hbeta , [OIII], \halpha and/or [NII] emission lines of 19\% of the AGN, while only 1. Read More

We highlight phenomenological aspects of Verlinde's recent proposal to account for the mass anomalies in galactic systems without dark matter -- in particular in their relation to MOND. Welcome addition to the MOND lore as it is, this approach have reproduced, so far, only a small fraction of MOND phenomenology, and is still rather tentative, both in its theoretical foundations and in its phenomenology. What Verlinde has extracted from this approach, so far, is a formula -- of rather limited applicability, and with no road to generalization in sight -- for the effective gravitational field of a spherical, isolated, static baryonic system. Read More

2016Dec
Authors: MicroBooNE Collaboration, R. Acciarri, C. Adams, R. An, A. Aparicio, S. Aponte, J. Asaadi, M. Auger, N. Ayoub, L. Bagby, B. Baller, R. Barger, G. Barr, M. Bass, F. Bay, K. Biery, M. Bishai, A. Blake, V. Bocean, D. Boehnlein, V. D. Bogert, T. Bolton, L. Bugel, C. Callahan, L. Camilleri, D. Caratelli, B. Carls, R. Castillo Fernandez, F. Cavanna, S. Chappa, H. Chen, K. Chen, C. Y. Chi, C. S. Chiu, E. Church, D. Cianci, G. H. Collin, J. M. Conrad, M. Convery, J. Cornele, P. Cowan, J. I. Crespo-Anadon, G. Crutcher, C. Darve, R. Davis, M. Del Tutto, D. Devitt, S. Duffin, S. Dytman, B. Eberly, A. Ereditato, D. Erickson, L. Escudero Sanchez, J. Esquivel, S. Farooq, J. Farrell, D. Featherston, B. T. Fleming, W. Foreman, A. P. Furmanski, V. Genty, M. Geynisman, D. Goeldi, B. Goff, S. Gollapinni, N. Graf, E. Gramellini, J. Green, A. Greene, H. Greenlee, T. Griffin, R. Grosso, R. Guenette, A. Hackenburg, R. Haenni, P. Hamilton, P. Healey, O. Hen, E. Henderson, J. Hewes, C. Hill, K. Hill, L. Himes, J. Ho, G. Horton-Smith, D. Huffman, C. M. Ignarra, C. James, E. James, J. Jan de Vries, W. Jaskierny, C. M. Jen, L. Jiang, B. Johnson, M. Johnson, R. A. Johnson, B. J. P. Jones, J. Joshi, H. Jostlein, D. Kaleko, L. N. Kalousis, G. Karagiorgi, T. Katori, P. Kellogg, W. Ketchum, J. Kilmer, B. King, B. Kirby, M. Kirby, E. Klein, T. Kobilarcik, I. Kreslo, R. Krull, R. Kubinski, G. Lange, F. Lanni, A. Lathrop, A. Laube, W. M. Lee, Y. Li, D. Lissauer, A. Lister, B. R. Littlejohn, S. Lockwitz, D. Lorca, W. C. Louis, G. Lukhanin, M. Luethi, B. Lundberg, X. Luo, G. Mahler, I. Majoros, D. Makowiecki, A. Marchionni, C. Mariani, D. Markley, J. Marshall, D. A. Martinez Caicedo, K. T. McDonald, D. McKee, A. McLean, J. Mead, V. Meddage, T. Miceli, G. B. Mills, W. Miner, J. Moon, M. Mooney, C. D. Moore, Z. Moss, J. Mousseau, R. Murrells, D. Naples, P. Nienaber, B. Norris, N. Norton, J. Nowak, M. OBoyle, T. Olszanowski, O. Palamara, V. Paolone, V. Papavassiliou, S. F. Pate, Z. Pavlovic, R. Pelkey, M. Phipps, S. Pordes, D. Porzio, G. Pulliam, X. Qian, J. L. Raaf, V. Radeka, A. Rafique, R. A Rameika, B. Rebel, R. Rechenmacher, S. Rescia, L. Rochester, C. Rudolf von Rohr, A. Ruga, B. Russell, R. Sanders, W. R. Sands III, M. Sarychev, D. W. Schmitz, A. Schukraft, R. Scott, W. Seligman, M. H. Shaevitz, M. Shoun, J. Sinclair, W. Sippach, T. Smidt, A. Smith, E. L. Snider, M. Soderberg, M. Solano-Gonzalez, S. Soldner-Rembold, S. R. Soleti, J. Sondericker, P. Spentzouris, J. Spitz, J. St. John, T. Strauss, K. Sutton, A. M. Szelc, K. Taheri, N. Tagg, K. Tatum, J. Teng, K. Terao, M. Thomson, C. Thorn, J. Tillman, M. Toups, Y. T. Tsai, S. Tufanli, T. Usher, M. Utes, R. G. Van de Water, C. Vendetta, S. Vergani, E. Voirin, J. Voirin, B. Viren, P. Watkins, M. Weber, T. Wester, J. Weston, D. A. Wickremasinghe, S. Wolbers, T. Wongjirad, K. Woodruff, K. C. Wu, T. Yang, B. Yu, G. P. Zeller, J. Zennamo, C. Zhang, M. Zuckerbrot

This paper describes the design and construction of the MicroBooNE liquid argon time projection chamber and associated systems. MicroBooNE is the first phase of the Short Baseline Neutrino program, located at Fermilab, and will utilize the capabilities of liquid argon detectors to examine a rich assortment of physics topics. In this document details of design specifications, assembly procedures, and acceptance tests are reported. Read More

We present results on the variation of 7.7 micron Polycyclic Aromatic Hydrocarbon (PAH) emission in galaxies spanning a wide range in metallicity at z ~ 2. For this analysis, we use rest-frame optical spectra of 476 galaxies at 1. Read More

We present results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on the identification, selection biases, and host galaxy properties of 55 X-ray, IR and optically-selected active galactic nuclei (AGN) at $1.4 < z < 3.8$. Read More

We present measurements of the electron-temperature based oxygen abundance for a highly star-forming galaxy at z=3.08, COSMOS-1908. This is the highest redshift at which [OIII]$\lambda$4363 has been detected, and the first time that this line has been measured at z>2. Read More

We present the first direct comparison between Balmer line and panchromatic SED-based SFRs for z~2 galaxies. For this comparison we used 17 star-forming galaxies selected from the MOSFIRE Deep Evolution Field (MOSDEF) survey, with $3\sigma$ detections for H$\alpha$ and at least two IR bands (Spitzer/MIPS 24$\mu$m and Herschel/PACS 100 and 160$\mu$m, and in some cases Herschel/SPIRE 250, 350, and 500$\mu$m). The galaxies have total IR (8-1000$\mu$m) luminosities of $\sim10^{11. Read More

We present H$\alpha$ gas kinematics for 178 star-forming galaxies at z~2 from the MOSFIRE Deep Evolution Field survey. We have developed models to interpret the kinematic measurements from fixed-angle multi-object spectroscopy, using structural parameters derived from CANDELS HST/F160W imaging. For 35 galaxies we measure resolved rotation with a median $(V/\sigma_{V,0})_{R_E}=2. Read More

Using observations from the MOSFIRE Deep Evolution Field (MOSDEF) survey, we investigate the physical conditions of star-forming regions in $z\sim2.3$ galaxies, specifically the electron density and ionization state. From measurements of the [O II]$\lambda\lambda$3726,3729 and [S II]$\lambda\lambda$6716,6731 doublets, we find a median electron density of $\sim250$ cm$^{-3}$ at $z\sim2. Read More

We present results on the dust attenuation curve of z~2 galaxies using early observations from the MOSFIRE Deep Evolution Field (MOSDEF) survey. Our sample consists of 224 star-forming galaxies with nebular spectroscopic redshifts in the range z= 1.36-2. Read More

We present results on the excitation properties of z~2.3 galaxies using early observations from the MOSFIRE Deep Evolution Field (MOSDEF) Survey. With its coverage of the full suite of strong rest-frame optical emission lines, MOSDEF provides an unprecedented view of the rest-frame optical spectra of a representative sample of distant star-forming galaxies. Read More

We present results on the z~2.3 mass-metallicity relation (MZR) using early observations from the MOSFIRE Deep Evolution Field (MOSDEF) survey. We use an initial sample of 87 star-forming galaxies with spectroscopic coverage of H\beta, [OIII]\lambda 5007, H\alpha, and [NII]\lambda 6584 rest-frame optical emission lines, and estimate the gas-phase oxygen abundance based on the N2 and O3N2 strong-line indicators. Read More

I review the history and development of Modified Newtonian Dynamics (MOND) beginning with the phenomenological basis as it existed in the early 1980s. I consider Milgrom's papers of 1983 introducing the idea and its consequences for galaxies and galaxy groups, as well as the initial reactions, both negative and positive. The early criticisms were primarily on matters of principle, such as the absence of conservation laws and perceived cosmological problems; an important step in addressing these issues was the development of the Lagrangian-based non-relativistic theory of Bekenstein and Milgrom. Read More

Microsystems become part of everyday life but their application is restricted by lack of strong and fast motors (actuators) converting energy into motion. For example, widespread internal combustion engines cannot be scaled down because combustion reactions are quenched in a small space. Here we present an actuator with the dimensions 100x100x5 um^3 that is using internal combustion of hydrogen and oxygen as part of its working cycle. Read More

The LUX experimental group has just announced the most stringent upper limits so far obtained on the cross section of WIMP-nucleon elastic scattering [1]. This result is a factor of two to five below the previous best upper limit [2] and effectively rules out earlier suggestions of low mass WIMP detection signals. The experimental expertise exhibited by this group is extremely impressive, but the fact of continued negative results raises the more basic question of whether or not this is the right approach to solving the dark matter problem. Read More

I show that the lensing masses of the SLACS sample of strong gravitational lenses are consistent with the stellar masses determined from population synthesis models using the Salpeter IMF. This is true in the context of both General Relativity and modified Newtonian dynamics, and is in agreement with the expectation of MOND that there should be little classical discrepancy within the high surface brightness regions probed by strong gravitational lensing. There is also dynamical evidence from this sample supporting the claim that the mass-to-light ratio of the stellar component increases with the velocity dispersion. Read More

A workshop was held at Fermilab on March 20-21, 2013 to discuss the development of liquid argon time projection chambers (LArTPC) in the United States. The workshop was organized under the auspices of the Coordinating Panel for Advanced Detectors, a body that was initiated by the American Physical Society Division of Particles and Fields. All presentations at the workshop were made in plenary sessions organized into seven topical categories: $i)$ Argon Purity, $ii)$ Cryogenics, $iii)$ TPC and High Voltage, $iv)$ Electronics, Data Acquisition and Triggering, $v)$ Scintillation Light Detection, $vi)$ Calibration and Test Beams, and $vii)$ Software. Read More

We have analyzed OGLE-III photometry for stars in the SMC cluster NGC 299. Two eclipsing binaries and one intrinsic variable (most likely a Be star) are identified. Unlike other young SMC clusters, no low-amplitude pulsating variables are present. Read More

Water electrolysis in a microsystem is observed and analyzed on a short-time scale ~10 us. Very unusual properties of the process are stressed. An extremely high current density is observed because the process is not limited by the diffusion of electroactive species. Read More

The ArgoNeuT liquid argon time projection chamber has collected thousands of neutrino and antineutrino events during an extended run period in the NuMI beam-line at Fermilab. This paper focuses on the main aspects of the detector layout and related technical features, including the cryogenic equipment, time projection chamber, read-out electronics, and off-line data treatment. The detector commissioning phase, physics run, and first neutrino event displays are also reported. Read More

I argue that, despite repeated claims of Ibata et al., the globular cluster NGC 2419 does not pose a problem for modified Newtonian dynamics (MOND). I present a new polytropic model with a running polytropic index. Read More

Wojtak, Hansen and Hjorth have recently claimed to confirm general relativity and to rule out the tensor-vector-scalar (TeVeS) gravitational theory based on an analysis of the gravitational redshifts of galaxies in 7800 clusters. But their ubiquitous modeling of the sources of cluster gravitational fields with Navarro-Frenk-White mass profiles is neither empirically justified out to the necessary radii in clusters, nor germane in the case of TeVeS. Using MONDian isothermal sphere models consistently constructed within MOND (equivalent to TeVeS models), we can fit the determined redshifts no worse than does general relativity with dark halos. Read More

I show that, in the context of MOND, non-isothermal models, approximated by high order polytropic spheres, are consistent with the observations of the radial distribution of the line-of-sight velocity dispersion in the distant globular cluster, NGC 2419. This calls into question the claim by Ibata et al. that the object constitutes a severe challenge for MOND. Read More

Ho\v{r}ava gravity is a attempt to construct a renormalizable theory of gravity by breaking the Lorentz Invariance of the gravitational action at high energies. The underlying principle is that Lorentz Invariance is an approximate symmetry and its violation by gravitational phenomena is somehow hidden to present limits of observational precision. Here I point out that a simple modification of the low energy limit of Ho\v{r}ava gravity in its non-projectable form can effectively camouflage the presence of a preferred frame in regions where the Newtonian gravitational field gradient is higher than $cH_0$; this modification results in the phenomenology of MOND at lower accelerations. Read More

The chapter describes the modeling of a material handling system with the production of individual units in a scheduled order. The units represent the agents in the model and are transported in the system which is abstracted as a directed graph. Since the hindrances of units on their path to the destination can lead to inefficiencies in the production, the blockages of units are to be reduced. Read More

Dwarf and low surface brightness galaxies are ideal objects to test modified Newtonian dynamics (MOND), because in most of these galaxies the accelerations fall below the threshold below where MOND supposedly applies. We have selected from the literature a sample of 27 dwarf and low surface brightness galaxies. MOND is successful in explaining the general shape of the observed rotation curves for roughly three quarters of the galaxies in the sample presented here. Read More

In the context of modified Newtonian dynamics, the fundamental plane, as the observational signature of the Newtonian virial theorem, is defined by high surface brightness objects that deviate from being purely isothermal: the line-of-sight velocity dispersion should slowly decline with radius as observed in luminous elliptical galaxies. All high surface brightness objects (e.g. Read More

MOND-- modified Newtonian dynamics-- may be viewed as an algorithm for calculating the distribution of force in an astronomical object from the observed distribution of baryonic matter. The fact that it works for galaxies is quite problematic for Cold Dark Matter. Moreover, MOND explains or subsumes systematic aspects of galaxy photometry and kinematics-- aspects that CDM does not address or gets wrong. Read More

Bolton et al. (2007) have derived a mass-based fundamental plane using photometric and spectroscopic observations of 36 strong gravitational lenses. The lensing allows a direct determination of the mass-surface density and so avoids the usual dependence on mass-to-light ratio. Read More

Beginning with a simple model for the growth of structure, I consider the dissipationless evolution of a MOND-dominated region in an expanding Universe by means of a spherically symmetric N-body code. I demonstrate that the final virialized objects resemble elliptical galaxies with well-defined relationships between the mass, radius, and velocity dispersion. These calculations suggest that, in the context of MOND, massive elliptical galaxies may be formed early (z > 10) as a result of monolithic dissipationless collapse. Read More

MOND predicts that a mass, M, contained within its transition radius r_t=(MG/a0)^{1/2}, may exhibit a feature at about that radius in the form of a shell, or projected ring, in the deduced distribution of its phantom dark matter. This occurs despite the absence of any underlying feature in the true (``baryon'') source distribution itself. The phenomenon is similar to the appearance of an event horizon and other unusual physics ``in the middle of nothing'' near the transition radius of General Relativity $MG/c^2$. Read More

The dynamical mass of clusters of galaxies, calculated in terms of modified Newtonian dynamics, is a factor of two or three times smaller than the Newtonian dynamical mass but remains significantly larger than the observed baryonic mass in the form of hot gas and stars in galaxies. Here I consider further the suggestion that the undetected matter might be in the form of cosmological neutrinos with mass on the order of 2 eV. If the neutrinos and baryons have comparable velocity dispersions and if the two components maintain their cosmological density ratio, then the electron density in the cores of clusters should be proportional to temperature to the 3/2 power, as appears to be true in non-cooling flow clusters. Read More

We extend the MOND analysis to a sample of 17 high surface brightness, early-type disc galaxies with rotation curves derived from a combination of 21cm HI line observations and optical spectroscopic data. A number of these galaxies have asymptotic rotation velocities between 250 and 350 km/s making them among the most massive systems (in terms of baryonic mass) considered in the context of MOND. We find that the general MOND prediction for such galaxies -- a rotation curve which gradually declines to the asymptotic value -- is confirmed, and in most cases the MOND rotation curve, determined from the mean radial light and gas distribution, agrees in detail with the observed rotation curve. Read More

Below a threshold energy, gas in the constant density core of a triaxial galaxy can find no simple non-intersecting periodic orbit to act as an attractor for its trajectory (El-Zant et al. 2003). If a disc of gas arriving from further out in the galaxy dissipates sufficient energy to fall below this threshold, it will thereafter collapse into the very centre. Read More

We present MOND analysis for several of the lowest mass disc galaxies currently amenable to such analysis--with (baryonic) masses below 4x10^8 solar masses. The agreement is good, extending the validity of MOND and its predicted mass velocity relation, to such low masses. Read More

Any viable theory of modified Newtonian dynamcs (MOND) as modified gravity is likely to require fields in addition to the usual tensor field of General Relativity. For such theories the MOND phenomenology emerges from an effective fifth force probably associated with a scalar field. Here I consider the constraints imposed upon such theories by solar system phenomenology, primarily by the absence of significant deviations from inverse square attraction in the inner solar system as well as detectable local preferred frame effects. Read More

On an empirical level, the most successful alternative to dark matter in bound gravitational systems is the modified Newtonian dynamics, or MOND, proposed by Milgrom. Here I discuss the attempts to formulate MOND as a modification of General Relativity. I begin with a summary of the phenomenological successes of MOND and then discuss the various covariant theories that have been proposed as a basis for the idea. Read More

2005Sep

I review various ideas on MOND cosmology and structure formation beginning with non-relativistic models in analogy with Newtonian cosmology. I discuss relativistic MOND cosmology in the context of Bekenstein's theory and propose an alternative biscalar effective theory of MOND in which the acceleration parameter is identified with the cosmic time derivative of a matter coupling scalar field. Cosmic CDM appears in this theory as scalar field oscillations of the auxiliary "coupling strength" field. Read More

We first review the nonrelativistic lagrangian theory as a framework for the MOND equation. Obstructions to a relativistic version of it are discussed leading up to TeVeS, a relativistic tensor-vector-scalar field theory which displays both MOND and Newtonian limits. The whys for its particular structure are discussed and its achievements so far are summarized. Read More

I describe a tensor-vector-scalar theory that reconciles the galaxy scale success of modified Newtonian dynamics (MOND) with the cosmological scale evidence for CDM. The theory provides a cosmological basis for MOND in the sense that the predicted phenomenology only arises in a cosmological background. The theory contains an evolving effective potential, and scalar field oscillations in this potential comprise the cold dark matter; the de Broglie wavelength of these soft bosons, however, is sufficiently large that they cannot accumulate in galaxies. Read More

We examine two corollaries of MOND pertaining to the properties of the equivalent dark-matter halo. MOND predicts for pure exponential discs a tight relation involving the halo and disc scale lengths and the mean acceleration in the disc, which we find to test favorably against the Verheijen sample of Ursa Major galaxies. A correlation between halo and disc length scales is also apparent when the "maximum disc" contribution is assumed, but we demonstrate that this follows from the more general MOND prediction. Read More

I discuss the classical cosmological tests-- angular size-redshift, flux-redshift, and galaxy number counts-- in the light of the cosmology prescribed by the intepretation of CMB anisotropies. The discussion is somewhat of a primer for physicists, with emphasis upon the possible systematic uncertainties in the observations and their interpretation. Given the curious composition of the Universe inherent in the emerging cosmological model, I stress the value of searching for inconsistencies rather than concordance, and suggest that the prevailing mood of triumphalism in cosmology is premature. Read More

2003Sep
Affiliations: 1Weizmann Institute, 2Kapteyn Astronomical Institute
Category: Astrophysics

The recent findings of Romanowsky et al., of an ``unexpectedly'' small mass discrepancy within 5 effective radii in several elliptical galaxies, are not surprising in the context of MOND. As we show here, they are, in fact, in full concordance with its predictions. Read More

2002Dec
Authors: R. H. Sanders1
Affiliations: 1Kapteyn Astronomical Institute, Groningen, NL
Category: Astrophysics

X-ray emitting clusters of galaxies are considered in the context of modified Newtonian dynamics (MOND). I show that self-gravitating isothermal gas spheres are not good representations of rich clusters with respect to the radial gas density distribution as indicated by the X-ray surface brightness. Pure gas spheres with a density distribution described by a ``beta'' model, as observed, also fail because, with MOND, these objects are far from isothermal. Read More

Rotation curves for four spiral galaxies with recently determined Cepheid-based distances are reconsidered in terms of modified Newtonian dynamics (MOND). For two of the objects, NGC 2403 and NGC 7331, the rotation curves predicted by MOND are compatible with the observed curves when these galaxies are taken to be at the Cepheid distance. For NGC 3198, the largest distance for which reasonable agreement is obtained is 10% smaller than the Cepheid-based distance; i. Read More

Modified Newtonian dynamics (MOND) is an empirically motivated modification of Newtonian gravity or inertia suggested by Milgrom as an alternative to cosmic dark matter. The basic idea is that at accelerations below a0 ~ 10^{-8} cm/s^2 ~ cH0/6 the effective gravitational attraction approaches sqrt{gN*a0} where gN is the usual Newtonian acceleration. This simple algorithm yields flat rotation curves for spiral galaxies and a mass-rotation velocity relation of the form M ~ V^4 that forms the basis for the observed luminosity-rotation velocity relation-- the Tully-Fisher law. Read More

2001Jun
Authors: R. H. Sanders1
Affiliations: 1Kapteyn Astronomical Institute, NL
Category: Astrophysics

Milgrom has proposed that the appearance of discrepancies between the Newtonian dynamical mass and the directly observable mass in astronomical systems could be due to a breakdown of Newtonian dynamics in the limit of low accelerations rather than the presence of unseen matter. Milgrom's hypothesis, modified Newtonian dynamics or MOND, has been remarkably successful in explaining systematic properties of spiral and elliptical galaxies and predicting in detail the observed rotation curves of spiral galaxies with only one additional parameter-- a critical acceleration which is on the order of the cosmologically interesting value of $cH_o$. Here I review the empirical successes of this idea and discuss its possible extention to cosmology and structure formation. Read More

2000Nov
Authors: R. H. Sanders1
Affiliations: 1Kapteyn Astronomical Institute, Groningen, NL
Category: Astrophysics

I consider the growth of inhomogeneities in a low-density baryonic, vacuum energy-dominated universe in the context of modified Newtonian dynamics (MOND). I first write down a two-field Langrangian-based theory of MOND (non-relativistic), which embodies several assumptions such as constancy of the MOND acceleration parameter, association of a MOND force with peculiar accelerations only, and the deceleration of the Hubble flow as a background field which influences the dynamics of a finite size region. In the context of this theory, the equation for the evolution of spherically symmetric over-densities is non-linear and implies very rapid growth even in a low-density background, particularly at the epoch when the putative cosmological constant begins to dominate the Hubble expansion. Read More