Kapteyn Institute Preprints (1999)

Kapteyn Institute Preprint Service.

Preprints of the Kapteyn Institute.
Paper copies can be ordered at:
Kapteyn Institute
P.O. Box 800
9700 AV Groningen
The Netherlands
All the preprints are compressed using gzip.

2001 Preprints

* Preprint 340 The Kinematics of lopsided galaxies Edo Noordermeer, Linda S. Sparke, Stephen E. Levine (13-12-2001)
* Preprint 339 The Dynamics of S0 Galaxies and their Tully-Fisher relation Anne Mathieu, Michael Merrifield, Konrad Kuijken
* Preprint 338 Parsec-scale structure in the warm ISM from polarized galactic radio background observations M. Haverkorn, P. Katgert, A.G. de Bruyn
* Preprint 337 An HI Survey of the Centaurus and Sculptor Groups - Constraints on the space density of low mass galaxies. W.J.G. de Blok, M.A. Zwaan, M. Dijkstra, F.H. Briggs, K.C. Freeman
* Preprint 336 Far-Infrared/Millimetre Emission in 3C Sources. Dust in Radio Galaxies and Quasars Paola Andreani, Robert A.E. Fosbury, Ilse van Bemmel, Wolfram Freudling
* Preprint 335 ISO Spectroscopy of Compact HII Regions in the Galaxy. II Ionization and elemental abundances N.L. Martin-Hernandez, E. Peeters, C. Morisset, A.G.G.M. Tielens, P. Cox, P.R. Roelfsema, J.-P. Baluteau, D. Schaerer, J.S. Mathis, F. Damour, E. Churchwell, M.F. Kessler
 
* Preprint 340 Atomic and Molecular Gas in the Merger Galaxy NGC 1316 (Fornax A) and its Environment C. Horellou, J.H. Black, J.H. van Gorkom, F. Combes, J.M. van der Hulst, V. Charmandaris
* Preprint 339 Modified Newtonian Dynamics and its Implications R.H. Sanders
* Preprint 338 U, B and r Band Luminosity Functions of Galaxies in the Coma Cluster Marco Beijersbergen, Henk Hoekstra, Pieter G. van Dokkum, Thijs van der Hulst
* Preprint 337 The Nearby Gield Galaxy Survey: A Spectrophotometric and photometric Study of Nearby Galaxies R.A. Jansen, S.J. Kannappan
* Preprint 336 The Evolution of Stellar Exponential Discs Annette Ferguson, Cathie Clarke
* Preprint 335 Strong Gravitational Lensing by Multiple Galaxies Ole Moeller, A.W. Blain
* Preprint 334 The PAH emission spectra of Large Magellanic Cloud HII regions R. Vermeij, E. Peeters, A.G.G.M. Tielens, J.M. van der Hulst
* Preprint 333 ISO spectroscopy of compact HII regions in the Galaxy : I. The catalogue E. Peeters, N.L. Martin-Hernandez, F. Damour, P. Cox, P.R. Roelfsema, J.-P. Baluteau, A.G.G.M. Tielens, E. Churchwell, M.F. Kessler, J.S. Mathis, C. Morisset and D. Schaerer
* Preprint 332 Did VV 29 collide with a dark Dark-Matter halo? F.H. Briggs, O. Moller, J.L. Higdon, N. Trentham, E. Ramirez-Ruiz
* Preprint 331 Two New Low Redshift 21cm Absorbers W.M. Lane, F.H. Briggs
* Preprint 330 Broad-line radio galaxies: old and feeble? Ilse van Bemmel, Peter Barthel
* Preprint 329 Kinematics and dynamics of the "superthin" edge-on disk galaxy IC 5249 P.C. van der Kruit, J. Jimenez-Vicente, M. Kregel, K.C. Freeman
* Preprint 328 Reconciling Damped Ly-alpha Statistics and 21cm Studies at z=0 Martin Zwaan, Frank Briggs, Marc Verheijen
* Preprint 327 A Targeted Survey for HI Clouds in Galaxy Groups Martin Zwaan
* Preprint 326 Cold Gas Kinematics in an L_* Spiral Galaxy at z=0.437: The Nature of Damped Lyman-alpha Absorbers F.H. Briggs, A.G. de Bruyn, R.C. Vermeulen
* Preprint 325 The CH out-of-plane bending modes of PAH molecules in astrophysical environments S. Hony, C. Van Kerckhoven, E. Peeters, A.G.G.M. Tielens, D.M. Hudgins, L.J. Allamandola
* Preprint 324 Extragalactic Planetary Nebula Kinematics with the WHT Aaron J. Romanowsky, Nigel G. Douglas, Magda Arnaboldi and Konrad Kuijken
* Preprint 323 Prospects for Radio Detection of the Epoch of Reionization and the Very First Stars F.H. Briggs
* Preprint 322 Millimeter observations of radio-loud active galaxies Ilse M. van Bemmel & Frank Bertoldi
* Preprint 321 The Evolution of GIPSY, or the Survival of an Image Processing System M.G.R. Vogelaar and J.P. Terlouw
* Preprint 320 The Ursa Major Cluster of Galaxies. IV. HI Synthesis Observations Marc A.W. Verheijen and Renzo Sancisi

The PAH emission spectra of Large Magellanic Cloud HII regions

R. Vermeij, E. Peeters, A.G.G.M. Tielens, J.M. van der Hulst

Preprint no. 334

Accepted for publication in Astronomy and Astrophysics.

Abstract

A set of ISOPHOT spectra from a sample of HII regions in the Large Magellanic Cloud (LMC) is presented. In all the spectra, emission bands arising from Polycyclic Aromatic Hydrocarbons (PAHs) are clearly present. These features are observed to vary considerably in relative strength to each-other from source to source and even within 30 Doradus. The LMC spectra have been compared with ISO-SWS spectra from Galactic HII regions and with the ISOCAM observation towards a quiescent molecular cloud in the SMC (Reach et al. 2000). A correlation is found between the I(7.7)/I(11.2) versus I(6.2)/I(11.2) and the I(8.6)/I(11.2) versus I(6.2)/I(11.2) ratios. A segregation between the sources in the different types of environment (Milky Way -- LMC -- SMC) is present. Furthermore, within the LMC observations, a clear distinction between 30 Doradus and non-30 Doradus pointings is found. We discuss the variations in the relative strength of the PAH features in view of the different physical environments and highlight the relation with the PAH/dust ratio and the extinction curve. We conclude that 1) the same conditions responsible for the observed trends in the relative PAH-feature strengths also affect the carrier of the 2175 A bump leading to the differences in strength of the latter, and 2) the molecular structure is the major cause of the observed variations in the relative strength of the PAH features. In the SMC and 30 Doradus compact PAH species dominate, while PAHs with an open, uneven structure are the dominant ones in Galactic HII regions and the non-30 Dor LMC sources.

ISO spectroscopy of compact HII regions in the Galaxy : I. The catalogue

E. Peeters, N.L. Martin-Hernandez, F. Damour, P. Cox, P.R. Roelfsema, J.-P. Baluteau, A.G.G.M. Tielens, E. Churchwell, M.F. Kessler, J.S. Mathis, C. Morisset and D. Schaerer

Preprint no. 333

Accepted for publication in Astronomy and Astrophysics.

Abstract

Infrared spectra between 2.3 and 196 mum were taken towards a sample of 45 compact HII regions using the two spectrometers (SWS and LWS) on board ISO. The primary goal is to determine the distribution of element abundances in the Galaxy, although there are also many other uses of this database. The spectra contain a wealth of information on the ionized gas and the associated photodissociation regions through the atomic fine-structure lines and on the dust properties via the dust emission bands and the continuum. Significant variations are found from source to source in both spectral shape and content. The sample of HII regions spans a wide range in galactocentric distance (from 0 to 22 kpc) enabling to investigate the variations of the nebular properties across the Galactic plane. The observations and the data reduction are described in detail in the present paper. The ISO spectral catalogue of compact HII regions contains the combined SWS-LWS spectra for each of the sources, the fluxes of the atomic fine-structure lines and hydrogen recombination lines, and an inventory of the spectra in terms of molecular lines, dust and ice bands.

Did VV 29 collide with a dark Dark-Matter halo?

F.H. Briggs, O. Moller, J.L. Higdon, N. Trentham, E. Ramirez-Ruiz

Preprint no. 332

Accepted for publication in Astronomy and Astrophysics.

Abstract

Westerbork Radio Synthesis Telescope observation of the galaxy VV29=Arp188=UGC10214 shows that there are at least three distinct dynamical components whose kinematics can be traced in 21cm line emission. The system appears to be the result of a galaxy-galaxy interaction. We identify a sufficient number of dynamical elements containing baryons (stars and neutral gas) that there is no compelling reason to postulate the presence of an additional dark matter halo that is devoid of detectable baryons. The central galaxy VV29a is massive (V_rot = 330 km/s) and gas rich (M_HI = 6x10^9 Msolar). The distinctive optical plume (VV29b), which extends eastward from the main galaxy, is also gas rich (M_HI = 3x10^9 Msolar) and has a very low gradient in line of sight velocity (<30 km/s) over 70kpc. On the western side, there is an HI feature of M_HI = 4x10^8 Msolar that participates strongly in orbital motion about the host in the same sense of rotation as the VV29a itself. A blue, less massive, gas-rich galaxy "VV29c" (M_HI = 9x10^8 Msolar) appears clearly in the HI maps as an 170 km/s wide spectral feature, seen in projection against or, more likely, behind the west side of the host disk. Its high recessional velocity is counter to the host rotation direction. The optical images of Trentham et al (2001) show signs of this blue dwarf against the redder VV29a disk. The companion galaxy CGCG27-021=MGC09-26-54 (at projected distance 115 kpc) is not detected in 21cm line emission (M_HI<10^9Msolar).

Two New Low Redshift 21cm Absorbers

W.M. Lane, F.H. Briggs

Preprint no. 331

Accepted for publication in the Astrophysical Journal Letters.

Abstract

As part of a larger program to identify low redshift radio analogues of the damped Lyman-alpha (DLA) absorbers seen in the spectra of high redshift quasars, Westerbork Synthesis Radio Telescope (WSRT) observations have discovered two new HI 21cm absorption lines at z=0.394 and z=0.437 in the spectra of the radio sources B 0248+430 and B 1243-072 respectively. These sightlines and redshifts were selected for study on the basis of the previously known low ionization absorption lines of MgII, and neither has been observed in the Lyman-alpha line. The 21cm line observations provide information on column densities, temperatures and kinematics of the thickest cold neutral clouds in the absorbers.

Broad-line radio galaxies: old and feeble?

Ilse van Bemmel, Peter Barthel

Preprint no. 330

To be published in Astronomy and Astrophysics Letters.

Abstract

Far-infrared photometry of broad-line radio galaxies shows this class of AGN to consist of many hot and some cool infrared emitters, with peaks in their spectral energy distributions around 25 micron or longward of 60 micron, respectively.  Quantitative analysis indicates that this distribution relates to a substantial dispersion in the strength of the cool dust component: broad-line radio galaxies are relatively poor in large-scale dust. Possibly they have undergone a different merger evolution, or are relatively old AGN.

Kinematics and dynamics of the "superthin" edge-on disk galaxy IC 5249

P.C. van der Kruit, J. Jimenez-Vicente, M. Kregel, K.C. Freeman

Preprint no. 329

To be published in Astronomy and Astrophysics.

Abstract

We present spectroscopic observations of the stellar motions in the disk of the superthin edge-on spiral galaxy IC 5249 and re-analyse synthesis observations of the HI.

We find that the HI rotation curve rises initially to about 90-100 km/s, but contrary to the conclusion of Abe et al. (1999) flattens well before the edge of the optical disk. Over most part of the optical disk we have been able to establish that the (tangential) stellar velocity dispersion is 25-30 km/s. We argue that the central light concentration in the disk is not a bulge in the classical Population II sense, but most likely represents structure in the disk component. From earlier surface photometry we adopt a value for the radial scalelength of the disk of 71 kpc, a vertical scaleheight of 0.650.05 kpc and a disk truncation radius of 171 kpc. The HI disk has a measurable thickness but from our analysis we conclude that this is due to a small inclination away from
perfectly edge-on. 

The very thin appearance of IC 5249 on the sky is the result of a combination of a low (face-on) surface brightness, a long scalelength and a a sharp truncation at only about 2.5 scalelengths. In terms of the ratio of the radial scalelength and the vertical scaleheight of the disk, IC 5249 is not very flat; in fact it is slightly fatter than the disk of our Galaxy. From various arguments we derive the stellar 
velocity dispersions at a position one radial scalelength out in the disk (R about 7 kpc) as respectively sigma_R about 35 km/s, sigma_{theta} about 30 km/s and sigma_z about 20 km/s. This is comparable to the values for the disk of our Galaxy in the solar neighborhood. Near the edge of the disk the ratio of radial to vertical velocity dispersion is probably higher.

Presumably the angular momentum distribution of the gas that formed the disk in IC 5249 was such that, compared to the Galaxy, a much more extended distribution resulted in spite of the lower overall rotation and mass. The low surface density that arose from that resulted in a thicker HI layer in which star formation proceeded ata much slower rate, but disk heating proceeded at a similar pace. 

Reconciling Damped Ly-alpha Statistics and 21cm Studies at z=0

Martin Zwaan, Frank Briggs, Marc Verheijen

Preprint no. 328

To appear in ASP Conference Series "Extragalactic Gas at Low Redshift", J. Mulchaey and J. Stocke, eds.

Abstract

Blind 21cm surveys in the local universe have shown that the local HI mass density, Omega_HI, is dominated by luminous, high surface brightness, spiral galaxies. On the other hand, surveys for host galaxies of damped Ly-alpha systems have not always been successful in finding bright spiral galaxies. From an analysis of 21cm aperture synthesis maps of nearby galaxies we show that this apparent contradiction can be resolved by realizing that the HI mass density is dominated by L* galaxies, but the HI cross section near the DLA threshold is more evenly distributed over galaxies with a large range in luminosity, gas mass, and surface brightness. The distributions of column densities and impact parameters of optically identified and non-identified DLA host galaxies in the literature and the HI maps are qualitatively in agreement. Due to poor number statistics of low redshift DLA systems, there is no firm indication that the redshift number count of low redshift DLA systems is inconsistent with that calculated from the nearby galaxy population.

A Targeted Survey for HI Clouds in Galaxy Groups

Martin Zwaan

Preprint no. 327

Accepted for publication in MNRAS

Abstract

Five galaxy groups with properties similar to those of the Local Group have been surveyed for HI clouds with the Arecibo Telescope. In total 300 pointings have been observed on grids of approximately 2.5 x 1.5 Mpc centred on the groups. The 4.5 sigma detection limit on the minimal detectable HI masses is approximately 7 x 10^6 M_sun (H_0=65). All detections could be attributed to optical galaxies; no significant detections of HI clouds have been made. This null result leads to the conclusion that the total HI mass of intragroup clouds must be less than 10 per cent of the total HI mass of galaxy groups and less than 0.05 per cent of the dynamical mass. The recent hypothesis that Galactic high velocity clouds are Local Group satellite galaxies is highly inconsistent with these observations.

Cold Gas Kinematics in an L_* Spiral Galaxy at z=0.437: The Nature of Damped Lyman-alpha Absorbers

F.H. Briggs, A.G. de Bruyn, R.C. Vermeulen

Preprint no. 326

Accepted for publication in Astronomy and Astrophysics

Abstract

Westerbork Radio Synthesis Telescope observations of the redshifted 21cm line absorber against the z_{em} = 0.871 double lobed quasar 3C196 show that the intervening absorber is %identified unambiguously with an L approx L_* spiral galaxy (3C196-G1) and that the absorbing layer of cold gas extends to radii of at least 30 h_50^{-1} kpc. The new data solve several long standing puzzles about this system by (1) discovering a second 21cm absorption feature, corresponding to absorption against the NE lobe of the background radio source and (2) spatially "resolving" the two absorption features to isolate the absorption along the two lines of sight to the opposing radio lobes. These findings resolve the disagreement in redshift between the UV metal and 21cm lines, and as well as demonstrating that the neutral layer does absorb both lobes of the background radio source. Simple kinematic models with an inclined, rotating gas disk match the observed 21cm profile and are also compatible with both the redshift and velocity spread of the absorption measured in UV resonance lines along a third, independent line of sight to the quasar nucleus and with the lack of 21cm absorption in as earlier VLBI experiment that was sensitive to opacity against the hot spot in the northern lobe. The inferred rotation speed and luminosity for the galaxy are compatible with the z approx 0 Tully-Fisher Relation. This system illustrates well how 21cm absorption against extended background radio sources is a powerful tool in determining the nature of the damped Lyman-alpha class of QSO absorption line system.

The CH out-of-plane bending modes of PAH molecules in astrophysical environments

S. Hony, C. Van Kerckhoven, E. Peeters, A.G.G.M. Tielens, D.M. Hudgins, L.J. Allamandola

Preprint no. 325

Accepted for publication in Astronomy and Astrophysics

Abstract

We present 10-15 um spectra of a sample of HII regions, YSOs and evolved stars that show strong unidentified infrared emission features, obtained with the ISO/SWS spectrograph onboard ISO. There spectra reveal a plethora of emission features with bands at 11.0, 11.2, 12.0, 12.7, 13.5 and 14.2 un. These features are observed to vary considerably in relative strength to each-other from source to source. In particular, the 10-15 um spectra of the evolved stars are dominated by the 11.2 un band while for HII regions the 12.7 is typically as strong as the 11.2 um band. Analysing the ISO data we find a good correlation between the 11.2 um band and the 3.3 band, and between the 12.7 um and the 6.2 um band. There is also a correlation between the ratio of the UIR band to the total dust emission and the 12.7 over 11.2 um ratio. Bands in the 10-15 um spectral region are due to CH out-of-plane (OOP) bending modes of polycyclic aromatic hydrocarbons (PAHs). We summarise existing laboratory data and theoretical quantum chemical calculations of these modes for meutral and cationic PAHs. Due to mode coupling, the exact peak position of these bands depends on the number of adjacent CH groups and hence the observed interstellar 10-15 um spectra can be used to determine the molecular structure of the insterstellar PAHs emitting in the different regions. We conclude that evolved stars predominantly inject compact 100-200 C-atoms PAHs into the ISM where they are subsequently processed, resulting in more open and uneven PAH structures.

Extragalactic Planetary Nebula Kinematics with the WHT

Aaron J. Romanowsky, Nigel G. Douglas, Magda Arnaboldi and Konrad Kuijken

Preprint no. 324

Accepted for publication in The ING Newsletter, Number 4, March 2001

Abstract

The use of planetary nebulae (PNe) as tracer particles is a promising approach for studying the kinematics of the outskirts of nearby elliptical galaxies. We report preliminary results from observations and modeling in the giant elliptical NGC 4472 (= M49), using the AUTOFIB2/WYFFOS multifibre spectrograph at the 4.2-m William Herschel Telescope. We also introduce the Planetary Nebula Spectrograph, a new instrument expressly designed for measuring the kinematics of PNe.

Prospects for Radio Detection of the Epoch of Reionization and the Very First Stars

F.H. Briggs

Preprint no. 323

To appear in : Gas & Galaxy Evolution (eds. J.E. Hibbard, M.P. Rupen, and J.H. van Gorkom), ASP Conference Series, 2000.

Abstract

The reionization of the intergalactic medium that takes place at redshift greater than 5, when the first stars or AGN ignite, may create a distinctive spatial and spectral signature in the radio background. Detection of a global signal might be measured in the near term with current technology and existing telescopes. Measurement of structures associated with the first pockets of ionization around stars requires a new telescope such as a Compact Lofar or SKA.

Millimeter observations of radio-loud active galaxies

Ilse M. van Bemmel& Frank Bertoldi

Preprint no. 322

Accepted for publication in Astronomy & Astrophysics.

Abstract

In order to study the nature of the far-infrared emission observed in radio-loud active galaxies, we have obtained 1.2 mm observations with the IRAM 30 m telescope for a sample of eight radio-loud active galaxies. In all objects we find that the 1.2 mm emission is dominated by non-thermal emission. An extrapolation of the non-thermal radio spectrum indicates that the contribution of synchrotron emission to the far-infrared is less than 10% in quasars, and negligible in the radio galaxies. The quasars in the sample show signs of relativistic beaming at millimeter wavelengths, and the quasar 3C334 shows evidence for strong variability.

The Evolution of GIPSY, or the Survival of an Image Processing System

M.G.R. Vogelaar and J.P. Terlouw

Preprint no. 321

To appear in the ASP conference proceedings: Data Analysis Software and Systems X (eds. F.A. Primini, F.R. Harnden, Jr., H.E. Payne).

Abstract

Since its introduction in the early seventies, GIPSY has constantly evolved. We present an overview of the developments over the last few years. These include the introduction of event-driven user interaction and the addition of a set of highly interactive graphical user interface (GUI) components. The GUI has been built on top of the existing user interface with which it is completely compatible. We also present examples of applications based on these developments.

The Ursa Major Cluster of Galaxies. IV. HI Synthesis Observations

Marc A.W. Verheijen and Renzo Sancisi

Preprint no. 320

Accepted for publication in Astronomy & Astrophysics.

Abstract

In this data paper we present the results of an extensive 21cm-line synthesis imaging survey of 43 spiral galaxies in the nearby Ursa Major cluster using the Westerbork Synthesis Radio Telescope. Detailed kinematic information in the form of position-velocity diagrams and rotation curves is presented in an atlas together with HI channel maps, 21cm continuum maps, global HI profiles, radial HI surface density profiles, integrated HI column density maps, and HI velocity fields. The relation between the corrected global HI linewidth and the rotational velocities Vmax and Vflat as derived from the rotation curves is investigated. Inclination angles obtained from the optical axis ratios are compared to those derived from the inclined HI disks and the HI velocity fields. The galaxies were not selected on the basis of their HI content but solely on the basis of their cluster membership and inclination which should be suitable for a kinematic analysis. The observed galaxies provide a well-defined, volume limited and equidistant sample, useful to investigate in detail the statistical properties of the Tully-Fisher relation and the dark matter halos around them.


Maintained by:  Gineke Alberts