Rene Walterbos - Academia.edu (original) (raw)
Properties of Galaxies by Rene Walterbos
A sample of 69 galaxies with radial velocities less than 2500 km s À1 was selected from the H i P... more A sample of 69 galaxies with radial velocities less than 2500 km s À1 was selected from the H i Parkes All Sky Survey (HiPASS) to deduce details about star formation in nearby disk galaxies selected with no bias to optical surface brightness selection effects. Broadband (B and R) and narrowband (H) images were obtained for all of these objects. More than half of the sample galaxies are late-type, dwarf disks (mostly Sc and Sm galaxies). We have measured the properties of the H ii regions on H continuum–subtracted images, using the HIIphot package developed by Thilker et al. All but one of the galaxies contained at least one detectable H ii region. Examination of the properties of the H ii regions in each galaxy revealed that the brightest regions in higher surface brightness galaxies tend to be more luminous than those in lower surface brightness galaxies. A higher fraction (referred to as the diffuse fraction) of the H emission from lower surface brightness galaxies comes from diffuse ionized gas. H ii region luminosity functions (LFs) co-added according to surface brightness show that the shapes of the LFs for the lowest surface brightness galaxies are different from those for typical spiral galaxies. This discrepancy could be caused by the lowest surface brightness galaxies having somewhat episodic star formation or by them forming a relatively larger fraction of their stars outside of dense, massive molecular clouds. In general, the results imply that the conditions under which star formation occurs in lower surface brightness galaxies are different than in more typical, higher surface brightness spiral galaxies.
Bookmarks Related papers MentionsView impact
Papers by Rene Walterbos
THE ASTRONOMICAL JOURNAL, 1999
We present the results of an ongoing investigation to provide a detailed view of the processes by... more We present the results of an ongoing investigation to provide a detailed view of the processes by which massive stars shape the surrounding interstellar medium (ISM), from parsec to kiloparsec scales. In this paper, we focus on studying the environments of Wolf-Rayet (W-R) stars in M31 to find evidence
for W-R windÈISM interactions, through imaging ionized hydrogen nebulae surrounding these stars. We have conducted a systematic survey for H II shells surrounding 48 of the 49 known W-R stars in M31. There are 17 W-R stars surrounded by single shells, or shell fragments, seven stars surrounded by concentric, limb-brightened shells, 20 stars where there is no clear physical association of the star with nearby Ha emission, and four stars that lack nearby Ha emission. Of the 17 + 7 shells above, there are
12 that contain one or two massive stars (including a W-R star) and that are
<= 40 pc in radius. These 12 shells may be classical W-R ejecta or windblown shells. Further, there may be excess Ha point-source emission associated with one of the 12 W-R stars surrounded by putative ejecta or windblown shells. There is also evidence for excess point-source emission associated with 11 other W-R stars. The excess emission may arise from unresolved circumstellar shells or within the extended outer envelopes of the stars themselves. In a few cases, we Ðnd clear morphological evidence for W-R shells interacting with each other. In several Ha images, we see W-R winds disrupting, or punching through, the walls of limb brightened
H II shells.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Star formation in low surface brightness (LSB) galaxies remains an enigma and several important o... more Star formation in low surface brightness (LSB) galaxies remains an enigma and several important observational paradoxes exist. In particular, although LSB disks are gas-rich, H I mapping has shown that they have typical H I column densities below the critical threshold for star formation. As of yet, no LSB galaxy has been detected in CO emission placing strict limits on
Bookmarks Related papers MentionsView impact
The Astrophysical Journal, 2001
Bookmarks Related papers MentionsView impact
The Astrophysical Journal, 2004
Bookmarks Related papers MentionsView impact
The Astrophysical Journal, 2005
Bookmarks Related papers MentionsView impact
The Astronomical Journal, 1996
Bookmarks Related papers MentionsView impact
We are currently conducting one of the most comprehensive studies of HII regions in spiral galaxi... more We are currently conducting one of the most comprehensive studies of HII regions in spiral galaxies. The STARFORM survey includes H-alpha imaging and HII region luminosity function analysis for a complete, magnitude-limited sample of 150 spiral galaxies (types Sa-Scd) that are located between 10 and 25 Mpc and have inclinations < 65 degrees. Our all-sky sample includes 31 Sa-Sab, 51 Sb-Sbc, and 68 Sc-Scd galaxies. We have already obtained H-alpha images for 60 spirals with the CTIO 1.5m telescope. Here we present the general properties of all HII regions detected in the southern hemisphere Sa-Sab galaxies drawn from our sample. Our luminosity function analysis is based on direct comparison with predictions from a population synthesis code which accounts for stochasticity in sparsely populated star clusters. We have just started to implement an observationally constrained correction for source blending by using archival HST imagery to quantify small-scale clustering properties of ...
Bookmarks Related papers MentionsView impact
Monthly Notices of the Royal Astronomical Society, 2008
Bookmarks Related papers MentionsView impact
Monthly Notices of the Royal Astronomical Society, 2009
Bookmarks Related papers MentionsView impact
![Research paper thumbnail of Detection of [O i ] λ6300 and Other Diagnostic Emission Lines in the Diffuse Ionized Gas of M33 with Gemini-North](https://attachments.academia-assets.com/88631298/thumbnails/1.jpg)
](The Astrophysical Journal, 2006
Bookmarks Related papers MentionsView impact
Astronomy & Astrophysics
Context. Studies of nearby galaxies reveal that around 50% of the total Hα luminosity in late-typ... more Context. Studies of nearby galaxies reveal that around 50% of the total Hα luminosity in late-type spirals originates from diffuse ionised gas (DIG), which is a warm, diffuse component of the interstellar medium that can be associated with various mechanisms, the most important ones being “leaking” HII regions, evolved field stars, and shocks. Aims. Using MUSE Wide Field Mode adaptive optics-assisted data, we study the condition of the ionised medium in the nearby (D = 3.4 Mpc) flocculent spiral galaxy NGC 7793 at a spatial resolution of ∼10 pc. We construct a sample of HII regions and investigate the properties and origin of the DIG component. Methods. We obtained stellar and gas kinematics by modelling the stellar continuum and fitting the Hα emission line. We identified the boundaries of resolved HII regions based on their Hα surface brightness. As a way of comparison, we also selected regions according to the Hα/[SII] line ratio; this results in more conservative boundaries. Usi...
Bookmarks Related papers MentionsView impact
Astronomy & Astrophysics
Aim. The vertical halo scale height is a crucial parameter to understand the transport of cosmic-... more Aim. The vertical halo scale height is a crucial parameter to understand the transport of cosmic-ray electrons (CRE) and their energy loss mechanisms in spiral galaxies. Until now, the radio scale height could only be determined for a few edge-on galaxies because of missing sensitivity at high resolution.Methods. We developed a sophisticated method for the scale height determination of edge-on galaxies. With this we determined the scale heights and radial scale lengths for a sample of 13 galaxies from the CHANG-ES radio continuum survey in two frequency bands.Results. The sample average values for the radio scale heights of the halo are 1.1 ± 0.3 kpc in C-band and 1.4 ± 0.7 kpc in L-band. From the frequency dependence analysis of the halo scale heights we found that the wind velocities (estimated using the adiabatic loss time) are above the escape velocity. We found that the halo scale heights increase linearly with the radio diameters. In order to exclude the diameter dependence, w...
Bookmarks Related papers MentionsView impact
The Astrophysical Journal Supplement Series
Bookmarks Related papers MentionsView impact
The Astronomical Journal
Bookmarks Related papers MentionsView impact
The Astronomical Journal
Bookmarks Related papers MentionsView impact
Symposium - International Astronomical Union, 1999
We have identified five new candidate LBVs in the NE half of M 31 and provide age limits for thes... more We have identified five new candidate LBVs in the NE half of M 31 and provide age limits for these objects through the color-magnitude diagrams of their potential parent OB associations. We note that three of the five candidates are not in OB associations nor are they in prominent H II regions.
Bookmarks Related papers MentionsView impact
The Astrophysical Journal, Mar 10, 1992
... Printed in USA PHYSICAL PROPERTIES OF NEUTRAL GAS IN M31 AND THE GALAXY ROBERTBRAUN Netherlan... more ... Printed in USA PHYSICAL PROPERTIES OF NEUTRAL GAS IN M31 AND THE GALAXY ROBERTBRAUN Netherlands Foundation for Research in Astronomy, Postbus 2, 7990 AA, Dwingeloo, The Netherlands; National Radio Astronomy Observatory, NM 87801 RENÉ AM ...
Bookmarks Related papers MentionsView impact
Astron J, 2002
Bookmarks Related papers MentionsView impact
A sample of 69 galaxies with radial velocities less than 2500 km s À1 was selected from the H i P... more A sample of 69 galaxies with radial velocities less than 2500 km s À1 was selected from the H i Parkes All Sky Survey (HiPASS) to deduce details about star formation in nearby disk galaxies selected with no bias to optical surface brightness selection effects. Broadband (B and R) and narrowband (H) images were obtained for all of these objects. More than half of the sample galaxies are late-type, dwarf disks (mostly Sc and Sm galaxies). We have measured the properties of the H ii regions on H continuum–subtracted images, using the HIIphot package developed by Thilker et al. All but one of the galaxies contained at least one detectable H ii region. Examination of the properties of the H ii regions in each galaxy revealed that the brightest regions in higher surface brightness galaxies tend to be more luminous than those in lower surface brightness galaxies. A higher fraction (referred to as the diffuse fraction) of the H emission from lower surface brightness galaxies comes from diffuse ionized gas. H ii region luminosity functions (LFs) co-added according to surface brightness show that the shapes of the LFs for the lowest surface brightness galaxies are different from those for typical spiral galaxies. This discrepancy could be caused by the lowest surface brightness galaxies having somewhat episodic star formation or by them forming a relatively larger fraction of their stars outside of dense, massive molecular clouds. In general, the results imply that the conditions under which star formation occurs in lower surface brightness galaxies are different than in more typical, higher surface brightness spiral galaxies.
Bookmarks Related papers MentionsView impact
THE ASTRONOMICAL JOURNAL, 1999
We present the results of an ongoing investigation to provide a detailed view of the processes by... more We present the results of an ongoing investigation to provide a detailed view of the processes by which massive stars shape the surrounding interstellar medium (ISM), from parsec to kiloparsec scales. In this paper, we focus on studying the environments of Wolf-Rayet (W-R) stars in M31 to find evidence
for W-R windÈISM interactions, through imaging ionized hydrogen nebulae surrounding these stars. We have conducted a systematic survey for H II shells surrounding 48 of the 49 known W-R stars in M31. There are 17 W-R stars surrounded by single shells, or shell fragments, seven stars surrounded by concentric, limb-brightened shells, 20 stars where there is no clear physical association of the star with nearby Ha emission, and four stars that lack nearby Ha emission. Of the 17 + 7 shells above, there are
12 that contain one or two massive stars (including a W-R star) and that are
<= 40 pc in radius. These 12 shells may be classical W-R ejecta or windblown shells. Further, there may be excess Ha point-source emission associated with one of the 12 W-R stars surrounded by putative ejecta or windblown shells. There is also evidence for excess point-source emission associated with 11 other W-R stars. The excess emission may arise from unresolved circumstellar shells or within the extended outer envelopes of the stars themselves. In a few cases, we Ðnd clear morphological evidence for W-R shells interacting with each other. In several Ha images, we see W-R winds disrupting, or punching through, the walls of limb brightened
H II shells.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Star formation in low surface brightness (LSB) galaxies remains an enigma and several important o... more Star formation in low surface brightness (LSB) galaxies remains an enigma and several important observational paradoxes exist. In particular, although LSB disks are gas-rich, H I mapping has shown that they have typical H I column densities below the critical threshold for star formation. As of yet, no LSB galaxy has been detected in CO emission placing strict limits on
Bookmarks Related papers MentionsView impact
The Astrophysical Journal, 2001
Bookmarks Related papers MentionsView impact
The Astrophysical Journal, 2004
Bookmarks Related papers MentionsView impact
The Astrophysical Journal, 2005
Bookmarks Related papers MentionsView impact
The Astronomical Journal, 1996
Bookmarks Related papers MentionsView impact
We are currently conducting one of the most comprehensive studies of HII regions in spiral galaxi... more We are currently conducting one of the most comprehensive studies of HII regions in spiral galaxies. The STARFORM survey includes H-alpha imaging and HII region luminosity function analysis for a complete, magnitude-limited sample of 150 spiral galaxies (types Sa-Scd) that are located between 10 and 25 Mpc and have inclinations < 65 degrees. Our all-sky sample includes 31 Sa-Sab, 51 Sb-Sbc, and 68 Sc-Scd galaxies. We have already obtained H-alpha images for 60 spirals with the CTIO 1.5m telescope. Here we present the general properties of all HII regions detected in the southern hemisphere Sa-Sab galaxies drawn from our sample. Our luminosity function analysis is based on direct comparison with predictions from a population synthesis code which accounts for stochasticity in sparsely populated star clusters. We have just started to implement an observationally constrained correction for source blending by using archival HST imagery to quantify small-scale clustering properties of ...
Bookmarks Related papers MentionsView impact
Monthly Notices of the Royal Astronomical Society, 2008
Bookmarks Related papers MentionsView impact
Monthly Notices of the Royal Astronomical Society, 2009
Bookmarks Related papers MentionsView impact
The Astrophysical Journal, 2006
Bookmarks Related papers MentionsView impact
Astronomy & Astrophysics
Context. Studies of nearby galaxies reveal that around 50% of the total Hα luminosity in late-typ... more Context. Studies of nearby galaxies reveal that around 50% of the total Hα luminosity in late-type spirals originates from diffuse ionised gas (DIG), which is a warm, diffuse component of the interstellar medium that can be associated with various mechanisms, the most important ones being “leaking” HII regions, evolved field stars, and shocks. Aims. Using MUSE Wide Field Mode adaptive optics-assisted data, we study the condition of the ionised medium in the nearby (D = 3.4 Mpc) flocculent spiral galaxy NGC 7793 at a spatial resolution of ∼10 pc. We construct a sample of HII regions and investigate the properties and origin of the DIG component. Methods. We obtained stellar and gas kinematics by modelling the stellar continuum and fitting the Hα emission line. We identified the boundaries of resolved HII regions based on their Hα surface brightness. As a way of comparison, we also selected regions according to the Hα/[SII] line ratio; this results in more conservative boundaries. Usi...
Bookmarks Related papers MentionsView impact
Astronomy & Astrophysics
Aim. The vertical halo scale height is a crucial parameter to understand the transport of cosmic-... more Aim. The vertical halo scale height is a crucial parameter to understand the transport of cosmic-ray electrons (CRE) and their energy loss mechanisms in spiral galaxies. Until now, the radio scale height could only be determined for a few edge-on galaxies because of missing sensitivity at high resolution.Methods. We developed a sophisticated method for the scale height determination of edge-on galaxies. With this we determined the scale heights and radial scale lengths for a sample of 13 galaxies from the CHANG-ES radio continuum survey in two frequency bands.Results. The sample average values for the radio scale heights of the halo are 1.1 ± 0.3 kpc in C-band and 1.4 ± 0.7 kpc in L-band. From the frequency dependence analysis of the halo scale heights we found that the wind velocities (estimated using the adiabatic loss time) are above the escape velocity. We found that the halo scale heights increase linearly with the radio diameters. In order to exclude the diameter dependence, w...
Bookmarks Related papers MentionsView impact
The Astrophysical Journal Supplement Series
Bookmarks Related papers MentionsView impact
The Astronomical Journal
Bookmarks Related papers MentionsView impact
The Astronomical Journal
Bookmarks Related papers MentionsView impact
Symposium - International Astronomical Union, 1999
We have identified five new candidate LBVs in the NE half of M 31 and provide age limits for thes... more We have identified five new candidate LBVs in the NE half of M 31 and provide age limits for these objects through the color-magnitude diagrams of their potential parent OB associations. We note that three of the five candidates are not in OB associations nor are they in prominent H II regions.
Bookmarks Related papers MentionsView impact
The Astrophysical Journal, Mar 10, 1992
... Printed in USA PHYSICAL PROPERTIES OF NEUTRAL GAS IN M31 AND THE GALAXY ROBERTBRAUN Netherlan... more ... Printed in USA PHYSICAL PROPERTIES OF NEUTRAL GAS IN M31 AND THE GALAXY ROBERTBRAUN Netherlands Foundation for Research in Astronomy, Postbus 2, 7990 AA, Dwingeloo, The Netherlands; National Radio Astronomy Observatory, NM 87801 RENÉ AM ...
Bookmarks Related papers MentionsView impact
Astron J, 2002
Bookmarks Related papers MentionsView impact
Based on resolved stellar photometry from the Sloan Digital Sky Survey, we recently reported the ... more Based on resolved stellar photometry from the Sloan Digital Sky Survey, we recently reported the discovery of Andromeda IX, a new dwarf spheroidal satellite of M31 that is the lowest luminosity, lowest surface brightness galaxy found to date. We have been carrying out an extensive program of followup observations, using telescopes ranging from the 2.5m NOT to the 8m Gemini
Bookmarks Related papers MentionsView impact