Showing papers by "Marc Verheijen published in 2013"
TL;DR: In this article, the authors used measured vertical velocity dispersions of the disk stars to calculate dynamical mass surface densities (Sigma$}${dyn}$) of 30 spiral galaxies, which were carried out to test the maximum disk hypothesis and to quantify properties of their dark-matter halos.
Abstract: We present dynamically-determined rotation-curve mass decompositions of 30 spiral galaxies, which were carried out to test the maximum-disk hypothesis and to quantify properties of their dark-matter halos. We used measured vertical velocity dispersions of the disk stars to calculate dynamical mass surface densities ({$Sigma$}$_{dyn}$). By subtracting our observed atomic and inferred molecular gas mass surface densities from {$Sigma$}$_{dyn}$, we derived the stellar mass surface densities ({$Sigma$}$_{∗}$), and thus have absolute measurements of all dominant baryonic components of the galaxies. Using K-band surface brightness profiles (I$_K$), we calculated the K-band mass-to-light ratio of the stellar disks ({Upsilon}$_{∗}$ = {$Sigma$}$_{∗}$/I$_K$) and adopted the radial mean (overline${$mls$}$) for each galaxy to extrapolate {$Sigma$}$_{∗}$ beyond the outermost kinematic measurement. The derived overline${$mls$}$ of individual galaxies are consistent with all galaxies in the sample having equal {Upsilon}$_{∗}$. We find a sample average and scatter of mlab overline${$mls$}$mrab = 0.31 {plusmn} 0.07. Rotation curves of the baryonic components were calculated from their deprojected mass surface densities. These were used with circular-speed measurements to derive the structural parameters of the dark-matter halos, modeled as either a pseudo-isothermal sphere (pISO) or a Navarro-Frenk-White (NFW) halo. In addition to our dynamically determined mass decompositions, we also performed alternative rotation-curve decompositions by adopting the traditional maximum-disk hypothesis. However, the galaxies in our sample are submaximal, such that at 2.2 disk scale lengths (h$_R$) the ratios between the baryonic and total rotation curves (F$_b$$^{2.2hR}$) are less than 0.75. We find this ratio to be nearly constant between 1-6h$_R$ within individual galaxies. We find a sample average and scatter of mlab F$_b$$^{2.2hR}$mrab = 0.57 {plusmn} 0.07, with trends of larger F$_b$$^{2.2hR}$ for more luminous and higher-surface-brightness galaxies. To enforce these being maximal, we need to scale {Upsilon}$_{∗}$ by a factor 3.6 on average. In general, the dark-matter rotation curves are marginally better fit by a pISO than by an NFW halo. For the nominal-{Upsilon}$_{∗}$ (submaximal) case, we find that the derived NFW-halo parameters have values consistent with {$Lambda$}CDM N-body simulations, suggesting that the baryonic matter in our sample of galaxies has only had a minor effect on the dark-matter distribution. In contrast, maximum-{Upsilon}$_{∗}$ decompositions yield halo-concentration parameters that are too low compared to the {$Lambda$}CDM simulations. Appendix is available in electronic form at http://www.aanda.org
199 citations
TL;DR: In this article, the authors presented ionized gas and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as many as three K-band disk scale lengths.
Abstract: We present ionized-gas ([Oiii]{$λ$}5007 a) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as many as three K-band disk scale lengths (h$_R$). These data have been derived from PPak integral-field-unit spectroscopy from 4980-5370 a observed at a mean resolution of {$λ$}/{$Delta$}{$λ$} = 7700 ({$σ$}$_{inst}$ = 17 km s$^{-1}$). These data are a fundamental product of our survey and will be used in companion papers to, e.g., derive the detailed (baryonic+dark) mass budget of each galaxy in our sample. Our presentation provides a comprehensive description of the observing strategy and data reduction, including a robust measurement and removal of shift, scale, and rotation effects in the data due to instrumental flexure. Using an in-plane coordinate system determined by fitting circular-speed curves to our velocity fields, we derive azimuthally averaged rotation curves and line-of-sight velocity dispersion ({$σ$}$_{LOS}$) and luminosity profiles for both the stars and [Oiii]-emitting gas. Along with a clear presentation of the data, we demonstrate: (1) The [Oiii] and stellar rotation curves exhibit a clear signature of asymmetric drift with a rotation difference that is 11% of the maximum rotation speed of the galaxy disk, comparable to measurements in the solar neighborhood in the Milky Way. (2) The e-folding length of the stellar velocity dispersion (h$_{σ}$) is 2h$_R$ on average, as expected for a disk with a constant scale height and mass-to-light ratio, with a scatter that is notably smaller for massive, high-surface-brightness disks in the most luminous galaxies. (3) At radii larger than 1.5h$_R$, {$σ$}$_{LOS}$ tends to decline slower than the best-fitting exponential function, which may be due to an increase in the disk mass-to-light ratio, disk flaring, or disk heating by the dark-matter halo. (4) A strong correlation exists between the central vertical stellar velocity dispersion of the disks ({$σ$}$_{z,0}$) and their circular rotational speed at 2.2h$_R$ (V$_{2.2hR}$$^{Oiii}$), with a zero point indicating that galaxy disks are submaximal. Moreover, weak but consistent correlations exist between {$σ$}$_{z,0}$/V$_{2.2hR}$$^{Oiii}$ and global galaxy properties such that disks with a fainter central surface brightness in bluer and less luminous galaxies of later morphological types are kinematically colder with respect to their rotational velocities. Based on observations collected at the Centro Astronomico Hispano Aleman (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut fur Astronomie and the Instituto de Astrof{i}sica de Andaluc{i}a (CSIC).Table 2 and Appendices are available in electronic form at http://www.aanda.org
110 citations
TL;DR: The Bluedisk project as discussed by the authors mapped the H i in a sample of 23 nearby galaxies with unusually high H i mass fractions, along with a similar-sized sample of control galaxies.
Abstract: We introduce the 'Bluedisk' project, a large programme at the Westerbork Synthesis Radio Telescope that has mapped the H i in a sample of 23 nearby galaxies with unusually high H i mass fractions, along with a similar-sized sample of control galaxies. This paper presents the sample selection, observational set-up, data reduction strategy and a first analysis of the sizes and structural properties of the H i discs. We find that the H i-rich galaxies lie on the same H i mass versus H i size relation as normal spiral galaxies, extending it to total H i masses of 2 x 10(10) M-circle dot and radii R1 of similar to 100 kpc. The H i-rich galaxies have significantly larger values of H i-to-optical size ratio and more clumpy H i discs than those of normal spirals. There is no evidence that the discs of H i-rich galaxies are more disturbed. In fact, the centre of the H i distribution corresponds more closely with the centre of the optical light in the H i-rich galaxies than in the controls. All these results argue against a scenario in which new gas has been brought in by mergers. It is possible that they may be more consistent with cooling from a surrounding quasi-static halo of warm/hot gas.
96 citations
TL;DR: For disc galaxies, a close relation exists between the distribution of light and the shape of the rotation curve as discussed by the authors, and the inner circular velocity gradient dRV(0) for spiral and irregular galaxies with high-quality rotation curves.
Abstract: For disc galaxies, a close relation exists between the distribution of light and the shape of the rotation curve. We quantify this relation by measuring the inner circular-velocity gradient dRV(0) for spiral and irregular galaxies with high-quality rotation curves. We find that dRV(0) correlates with the central surface brightness μ0 over more than two orders of magnitude in dRV(0) and four orders of magnitudes in μ0. This is a scaling relation for disc galaxies. It shows that the central stellar density of a galaxy closely relates to the inner shape of the potential well, also for low-luminosity and low-surface-brightness galaxies that are expected to be dominated by dark matter.
69 citations
TL;DR: In this article, a pilot for an H I deep field done with the Karl G. Jansky Very Large Array (VLA) is presented, which takes advantage of the newly expanded capabilities of the telescope to probe the redshift interval 0 < z < 0.193 in one observation.
Abstract: High-resolution 21 cm H I deep fields provide spatially and kinematically resolved images of neutral hydrogen at different redshifts, which are key to understanding galaxy evolution across cosmic time and testing predictions of cosmological simulations. Here we present results from a pilot for an H I deep field done with the Karl G. Jansky Very Large Array (VLA). We take advantage of the newly expanded capabilities of the telescope to probe the redshift interval 0 < z < 0.193 in one observation. We observe the COSMOS field for 50 hr, which contains 413 galaxies with optical spectroscopic redshifts in the imaged field of 34' × 34' and the observed redshift interval. We have detected neutral hydrogen gas in 33 galaxies in different environments spanning the probed redshift range, including three without a previously known spectroscopic redshift. The detections have a range of H I and stellar masses, indicating the diversity of galaxies we are probing. We discuss the observations, data reduction, results, and highlight interesting detections. We find that the VLA's B-array is the ideal configuration for H I deep fields since its long spacings mitigate radio frequency interference. This pilot shows that the VLA is ready to carry out such a survey, and serves as a test for future H I deep fields planned with other Square Kilometer Array pathfinders.
67 citations
TL;DR: In this article, optical spectroscopy for the blind Ultra Deep H I Environmental Survey (BUD-HIES) is presented, which has detected H I in over 150 galaxies in and around two Abell clusters at z similar or equal to 0.2.
Abstract: We present the optical spectroscopy for the Blind Ultra Deep H I Environmental Survey (BUD-HIES). With the Westerbork Synthesis Radio Telescope, BUDHIES has detected H I in over 150 galaxies in and around two Abell clusters at z similar or equal to 0.2. With the aim of characterizing the environments of the H I-detected galaxies, we obtained multifibre spectroscopy with the William Herschel Telescope. In this paper, we describe the spectroscopic observations, report redshifts and EW[O II] measurements for similar to 600 galaxies, and perform an environmental analysis. In particular, we present cluster velocity dispersion measurements for five clusters and groups in the BUDHIES volume, as well as a detailed substructure analysis.
46 citations
Journal Article•
TL;DR: In this article, the authors studied a sample of 18 Blue Compact Dwarfs (BCDs) using both new and archival HI data and found that BCDs have a steeply-rising rotation curve that flattens in the outer parts.
Abstract: The mechanisms that trigger strong bursts of star formation in dwarf galaxies are poorly understood. Blue Compact Dwarfs (BCDs) are nearby starburst galaxies that may hold the key to understand these mechanisms. We are studying a sample of 18 BCDs using both new and archival HI data. In several cases we find that BCDs have a steeply-rising rotation curve that flattens in the outer parts. This points to a strong central concentration of mass. We introduce a new parameter to quantify the central mass concentration in dwarf galaxies (BCDs and irregulars): the circular-velocity gradient V(Rd)/Rd, where Rd is the galaxy scale-length. We find that V(Rd)/Rd correlates with i) the central surface brightness; ii) the mean HI surface density over the stellar disk; and iii) the SFR density. BCDs have higher V(Rd)/Rd than typical irregulars, suggesting that the starburst activity is closely linked with the gravitational potential and the concentration of gas. We decompose the rotation curves of BCDs into mass components and find that baryons (stars and gas) are dynamically important. This is remarkable, as dwarf galaxies are commonly thought to be entirely dominated by dark matter. We discuss the implications of these results on the evolution of dwarf galaxies and in particular on the properties of the progenitors and descendants of BCDs.
13 citations
TL;DR: For a rotating galaxy, the inner circular-velocity gradient d{R}V(0) provides a direct estimate of the central dynamical mass density, including gas, stars, and dark matter.
Abstract: For a rotating galaxy, the inner circular-velocity gradient d_{R}V(0) provides a direct estimate of the central dynamical mass density, including gas, stars, and dark matter. We consider 60 low-mass galaxies with high-quality HI and/or stellar rotation curves (including starbursting dwarfs, irregulars, and spheroidals), and estimate d_{R}V(0) as V(R_d)/R_d, where R_d is the galaxy scale-length. For gas-rich dwarfs, we find that V(R_d)/R_d correlates with the central surface brightness mu(0), the mean atomic gas surface density Sigma_gas, and the star formation rate surface density Sigma_SFR. Starbursting galaxies, such as blue compact dwarfs (BCDs), generally have higher values of V(R_d)/R_d than dwarf irregulars, suggesting that the starburst is closely related to the inner shape of the potential well. There are, however, some "compact" irregulars with values of V(R_d)/R_d similar to BCDs. Unless a redistribution of mass takes place, BCDs must evolve into compact irregulars. Rotating spheroidals in the Virgo cluster follow the same correlation between V(R_d)/R_d and mu(0) as gas-rich dwarfs. They have values of V(R_d)/R_d comparable to those of BCDs and compact irregulars, pointing at evolutionary links between these types of dwarfs. Finally, we find that, similarly to spiral galaxies and massive starbursts, the star-formation activity in dwarfs can be parametrized as Sigma_SFR = epsilon*Sigma_gas/t_orb, where t_orb is the orbital time and epsilon = 0.02.
9 citations
TL;DR: In this paper, the authors used measured vertical velocity dispersions of the disk stars to calculate dynamical mass surface densities, and derived the stellar mass surface density, and thus have absolute measurements of all dominant baryonic components.
Abstract: We present dynamically-determined rotation-curve mass decompositions of 30 spiral galaxies, which were carried out to test the maximum-disk hypothesis and to quantify properties of their dark-matter (DM) halos. We used measured vertical velocity dispersions of the disk stars to calculate dynamical mass surface densities. Together with our atomic and molecular gas mass surface densities, we derived the stellar mass surface densities, and thus have absolute measurements of all dominant baryonic components. Using K-band surface brightness profiles, we calculated the K-band mass-to-light ratio of the stellar disks (M/L). Our result is consistent with all galaxies in the sample having equal M/L, with a sample average and scatter of =0.31+/-0.07. Rotation-curves of the baryonic components were calculated from their mass surface densities, and used with circular-speed measurements to derive the structural parameters of the DM halos, modeled as either a pseudo-isothermal sphere (pISO) or an NFW halo. All galaxies in our sample are submaximal, such that at 2.2 disk scale lengths (hR) the ratios between the baryonic and total rotation-curves (Fb^{2.2hR}) are less than 0.75. We find this ratio to be nearly constant between 1-6 hR within individual galaxies. We find a sample average and scatter of =0.57+/-0.07, with trends of larger Fb^{2.2hR} for more luminous and higher-surface-brightness galaxies. To enforce these being maximal, we need to scale M/L by a factor 3.6 on average. The DM rotation curves are marginally better fit by a pISO than by an NFW halo. For the nominal-M/L (submaximal) case, the derived NFW-halo parameters have values consistent with LCDM N-body simulations, suggesting that the baryonic matter has only had a minor effect on the DM distribution. In contrast, maximum-M/L decompositions yield halo concentrations that are too low compared to the LCDM simulations.
3 citations
TL;DR: In this paper, the authors presented ionized-gas (OIII) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as much as three disk scale lengths (h_R).
Abstract: We present ionized-gas (OIII) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as much as three disk scale lengths (h_R). These data have been derived from PPak IFU spectroscopy (4980-5370A), observed at a mean resolution of R=7700 (sigma_inst=17km/s). These data are a fundamental product of our survey and will be used in companion papers to, e.g., derive the detailed (baryonic+dark) mass budget of each galaxy in our sample. Our presentation provides a comprehensive description of the observing strategy, data reduction, and analysis. Along with a clear presentation of the data, we demonstrate: (1) The OIII and stellar rotation curves exhibit a clear signature of asymmetric drift with a rotation difference that is 11% of the maximum rotation speed of the galaxy disk, comparable to measurements in the solar neighborhood in the Milky Way. (2) The e-folding length of the stellar velocity dispersion is two times h_R on average, as expected for a disk with a constant scale height and mass-to-light ratio, with a scatter that is notably smaller for massive, high-surface-brightness disks in the most luminous galaxies. (3) At radii larger than 1.5 h_R, the stellar velocity dispersion tends to decline slower than the best-fitting exponential function, which may be due to an increase in the disk mass-to-light ratio, disk flaring, or disk heating by the dark-matter halo. (4) A strong correlation exists between the central vertical stellar velocity dispersion of the disks and their circular rotational speed at 2.2 h_R, with a zero point indicating that galaxy disks are submaximal. Moreover, weak but consistent correlations exist such that disks with a fainter central surface brightness in bluer and less luminous galaxies of later morphological types are kinematically colder with respect to their rotational velocities.
2 citations
Posted Content•
TL;DR: In this paper, the stellar surface mass density (Sigma_*) and two-component (gas+stars) disk stability (Q_RW) for 25 late-type galaxies from the DiskMass Survey were calculated based on fits of a dynamical model to our ionized-gas and stellar kinematic data performed using a Markov Chain Monte Carlo sampling of the Bayesian posterior.
Abstract: We calculate the stellar surface mass density (Sigma_*) and two-component (gas+stars) disk stability (Q_RW) for 25 late-type galaxies from the DiskMass Survey. These calculations are based on fits of a dynamical model to our ionized-gas and stellar kinematic data performed using a Markov Chain Monte Carlo sampling of the Bayesian posterior. Marginalizing over all galaxies, we find a median value of Q_RW=2.0+/-0.9 at 1.5 scale lengths. We also find that Q_RW is anti-correlated with the star-formation rate surface density (Sigma_SFR), which can be predicted using a closed set of empirical scaling relations. Finally, we find that the star-formation efficiency (Sigma_SFR/Sigma_g) is correlated with Sigma_* and weakly anti-correlated with Q_RW. The former is consistent with an equilibrium prediction of Sigma_SFR/Sigma_g propto Sigma_*^{1/2}. Despite its order-of-magnitude range, we find no correlation of Sigma_SFR/Sigma_g/Sigma_*^{1/2} with any other physical quantity derived by our study.