In the cold dark matter cosmology, the baryonic components of galaxies-stars and gas-are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the ...total mass of the galaxy and its dark-matter halo. In the local (low-redshift) Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius-a hallmark of the dark-matter model. Comparisons between the dynamical mass, inferred from these velocities in rotational equilibrium, and the sum of the stellar and cold-gas mass at the peak epoch of galaxy formation ten billion years ago, inferred from ancillary data, suggest high baryon fractions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (owing to the chosen stellar initial-mass function and the calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter. Here we report rotation curves (showing rotation velocity as a function of disk radius) for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of a combination of two main factors: first, a large fraction of the massive high-redshift galaxy population was strongly baryon-dominated, with dark matter playing a smaller part than in the local Universe; and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early (high-redshift) Universe efficiently condensed at the centres of dark-matter haloes when gas fractions were high and dark matter was less concentrated.
We make publicly available a catalog of calibrated environmental measures for galaxies in the five 3D-Hubble Space Telescope (HST)/CANDELS deep fields. Leveraging the spectroscopic and grism ...redshifts from the 3D-HST survey, multiwavelength photometry from CANDELS, and wider field public data for edge corrections, we derive densities in fixed apertures to characterize the environment of galaxies brighter than mag in the redshift range . By linking observed galaxies to a mock sample, selected to reproduce the 3D-HST sample selection and redshift accuracy, each 3D-HST galaxy is assigned a probability density function of the host halo mass, and a probability that it is a central or a satellite galaxy. The same procedure is applied to a z = 0 sample selected from Sloan Digital Sky Survey. We compute the fraction of passive central and satellite galaxies as a function of stellar and halo mass, and redshift, and then derive the fraction of galaxies that were quenched by environment specific processes. Using the mock sample, we estimate that the timescale for satellite quenching is it is longer at lower stellar mass or lower redshift, but remarkably independent of halo mass. This indicates that, in the range of environments commonly found within the 3D-HST sample ( ), satellites are quenched by exhaustion of their gas reservoir in the absence of cosmological accretion. We find that the quenching times can be separated into a delay phase, during which satellite galaxies behave similarly to centrals at fixed stellar mass, and a phase where the star formation rate drops rapidly ( Gyr), as shown previously at z = 0. We conclude that this scenario requires satellite galaxies to retain a large reservoir of multi-phase gas upon accretion, even at high redshift, and that this gas sustains star formation for the long quenching times observed.
We present a census of ionized gas outflows in 599 normal galaxies at redshift 0.6 < z < 2.7, mostly based on integral field spectroscopy of Hα, N ii, and S ii line emission. The sample fairly ...homogeneously covers the main sequence of star-forming galaxies with masses 9.0 < log(M */M ⊙) < 11.7, and probes into the regimes of quiescent galaxies and starburst outliers. About one-third exhibits the high-velocity component indicative of outflows, roughly equally split into winds driven by star formation (SF) and active galactic nuclei (AGNs). The incidence of SF-driven winds correlates mainly with SF properties. These outflows have typical velocities of ∼450 km s−1, local electron densities of n e ∼ 380 cm−3, modest mass loading factors of ∼0.1–0.2 at all galaxy masses, and energetics compatible with momentum driving by young stellar populations. The SF-driven winds may escape from log(M */M ⊙) ≲ 10.3 galaxies, but substantial mass, momentum, and energy in hotter and colder outflow phases seem required to account for low galaxy formation efficiencies in the low-mass regime. Faster AGN-driven outflows (∼1000–2000 km s−1) are commonly detected above log(M */M ⊙) ∼ 10.7, in up to ∼75% of log(M */M ⊙) ≳ 11.2 galaxies. The incidence, strength, and velocity of AGN-driven winds strongly correlates with stellar mass and central concentration. Their outflowing ionized gas appears denser (n e ∼ 1000 cm−3), and possibly compressed and shock-excited. These winds have comparable mass loading factors as the SF-driven winds but carry ∼10 (∼50) times more momentum (energy). The results confirm our previous findings of high-duty-cycle, energy-driven outflows powered by AGN above the Schechter mass, which may contribute to SF quenching.
We present the completed KMOS3D survey, an integral field spectroscopic survey of 739 \(\mathrm{log}({M}_{\star }/{M}_{\odot })\gt 9\) galaxies at 0.6 < z < 2.7 using the K-band Multi Object ...Spectrograph (KMOS) at the Very Large Telescope. The KMOS3D survey provides a population-wide census of kinematics, star formation, outflows, and nebular gas conditions both on and off the star-forming galaxy main sequence through the spatially resolved and integrated properties of Hα, N ii, and S ii emission lines. We detect Hα emission for 91% of galaxies on the main sequence of star formation and 79% overall. The depth of the survey has allowed us to detect galaxies with star formation rates below 1 M ⊙ yr−1, as well as to resolve 81% of detected galaxies with ≥3 resolution elements along the kinematic major axis. The detection fraction of Hα is a strong function of both color and offset from the main sequence, with the detected and nondetected samples exhibiting different spectral energy distribution shapes. Comparison of Hα and UV+IR star formation rates reveal that dust attenuation corrections may be underestimated by 0.5 dex at the highest masses (\(\mathrm{log}({M}_{\star }/{M}_{\odot })\gt 10.5\)). We confirm our first year results of a high rotation-dominated fraction (monotonic velocity gradient and v rot/\({\sigma }_{0}\gt \sqrt{3.36}\)) of 77% for the full KMOS3D sample. The rotation-dominated fraction is a function of both stellar mass and redshift, with the strongest evolution measured over the redshift range of the survey for galaxies with \(\mathrm{log}({M}_{\star }/{M}_{\odot })\lt 10.5\). With this paper, we include a final data release of all 739 observed objects (http://www.mpe.mpg.de/ir/KMOS3D).
We study a set of 3319 galaxies in the redshift interval 0.04 < z < 0.15 with far-infrared (FIR) coverage from the Herschel Stripe 82 survey (HerS), and emission-line measurements, redshifts, stellar ...masses and star formation rates (SFRs) from the Sloan Digital Sky Survey (SDSS) (DR7) MPA/JHU data base. About 40 per cent of the sample are detected in the Herschel/SPIRE 250 μm band. Total infrared (TIR) luminosities derived from HerS and Wide-field Infrared Survey Explorer (WISE) photometry allow us to compare infrared and optical estimates of SFR with unprecedented statistics for diverse classes of galaxies. We find excellent agreement between TIR-derived and emission line-based SFRs for H ii galaxies. Other classes, such as active galaxies and evolved galaxies, exhibit systematic discrepancies between optical and TIR SFRs. We demonstrate that these offsets are attributable primarily to survey biases and the large intrinsic uncertainties of the Dn
4000- and colour-based optical calibrations used to estimate the SDSS SFRs of these galaxies. Using a classification scheme which expands upon popular emission-line methods, we demonstrate that emission-line galaxies with uncertain classifications include a population of massive, dusty, metal-rich star-forming systems that are frequently neglected in existing studies. We also study the capabilities of infrared selection of star-forming galaxies. FIR selection reveals a substantial population of galaxies dominated by cold dust which are missed by the long-wavelength WISE bands. Our results demonstrate that Herschel large-area surveys offer the means to construct large, relatively complete samples of local star-forming galaxies with accurate estimates of SFR that can be used to study the interplay between nuclear activity and star formation.
ABSTRACT We present a study of kinematic asymmetries from the integral field spectroscopic surveys MAGPI and SAMI. By comparing the asymmetries in the ionized gas and stars, we aim to disentangle the ...physical processes that contribute to kinematic disturbances. We normalize deviations from circular motion by S05, allowing us to study kinematic asymmetries in the stars and gas, regardless of kinematic temperature. We find a similar distribution of stellar asymmetries in galaxies where we do and do not detect ionized gas, suggesting that whatever is driving the stellar asymmetries does not always lead to gas removal. In both MAGPI and SAMI, we find an anticorrelation between stellar asymmetry and stellar mass, that is absent in the gas asymmetries. After stellar mass and mean-stellar-age matching distributions, we find that at all stellar masses, MAGPI galaxies display larger stellar asymmetry compared to SAMI galaxies. In both MAGPI and SAMI galaxies, we find that star-forming galaxies with old mean-stellar-ages typically have larger asymmetries in their gas compared to their stars, whereas galaxies with young mean-stellar-ages have larger asymmetries in their stars compared to their gas. We suggest that this results from continuous, clumpy accretion of gas.
Using integral field spectroscopy, we investigate the kinematic properties of 35 massive centrally dense and compact star-forming galaxies (SFGs; \(\mathrm{log}{\overline{M}}_{* }{M}_{\odot }=11.1\), ...\(\mathrm{log}({{\rm{\Sigma }}}_{1\mathrm{kpc}}{M}_{\odot }\,{\mathrm{kpc}}^{-2})\gt 9.5\), \(\mathrm{log}({M}_{* }/{r}_{e}^{1.5}{M}_{\odot }\,{\mathrm{kpc}}^{-1.5})\gt 10.3\)) at z ∼ 0.7–3.7 within the KMOS3D survey. We spatially resolve 23 compact SFGs and find that the majority are dominated by rotational motions with velocities ranging from 95 to 500 km s−1. The range of rotation velocities is reflected in a similar range of integrated Hα line widths, 75–400 km s−1, consistent with the kinematic properties of mass-matched extended galaxies from the full KMOS3D sample. The fraction of compact SFGs that are classified as “rotation-dominated” or “disklike” also mirrors the fractions of the full KMOS3D sample. We show that integrated line-of-sight gas velocity dispersions from KMOS3D are best approximated by a linear combination of their rotation and turbulent velocities with a lesser but still significant contribution from galactic-scale winds. The Hα exponential disk sizes of compact SFGs are, on average, 2.5 ± 0.2 kpc, 1–2נthe continuum sizes, in agreement with previous work. The compact SFGs have a 1.4נhigher active galactic nucleus (AGN) incidence than the full KMOS3D sample at fixed stellar mass with an average AGN fraction of 76%. Given their high and centrally concentrated stellar masses, as well as stellar-to-dynamical mass ratios close to unity, the compact SFGs are likely to have low molecular gas fractions and to quench on a short timescale unless replenished with inflowing gas. The rotation in these compact systems suggests that their direct descendants are rotating passive galaxies.
We analyze the angular momenta of massive star-forming galaxies (SFGs) at the peak of the cosmic star formation epoch (z~ 0.8-2.6). Our sample of ~360 log(M sub(*)/M sub(middot in circle)) ~ 9.3-11.8 ...SFGs is mainly based on the KMOS super(3D) and SINS/zC-SINF surveys of Halpha kinematics, and collectively provides a representative subset of the massive star-forming population. The inferred halo scale angular momentum distribution is broadly consistent with that theoretically predicted for their dark matter halos, in terms of mean spin parameter left angle bracketlambdaright angle bracket ~ 0.037 and its dispersion (sigma sub(loglambda)~ 0.2). Spin parameters correlate with the disk radial scale and with their stellar surface density, but do not depend significantly on halo mass, stellar mass, or redshift. Our data thus support the long-standing assumption that on average, even at high redshifts, the specific angular momentum of disk galaxies reflects that of their dark matter halos (j sub(d)= j sub(DM)). The lack of correlation between lambda x (j sub(d)/j sub(DM)) and the nuclear stellar density Sigma sub(*)(1 kpc) favors a scenario where disk-internal angular momentum redistribution leads to "compaction" inside massive high-redshift disks. For our sample, the inferred average stellar to dark matter mass ratio is ~2%, consistent with abundance matching results. Including the molecular gas, the total baryonic disk to dark matter mass ratio is ~5% for halos near 10 super(12)M sub(middot in circle), which corresponds to 31% of the cosmologically available baryons, implying that high-redshift disks are strongly baryon dominated.
Abstract Sacroiliac (SI) screw fixation represents an effective method to stabilise pelvic injuries. However, to date neither reliable radiological landmarks nor effective anatomical classifications ...of the sacrum exist. This study investigates the influence of variability in sacral shape on secure transverse SI-screw positioning. Furthermore, consistent correlations of these anatomical conditions are analysed with respect to standard planar pelvic views. For shape analysis, 80 human computed tomography data sets were segmented with the software Amira 4.2 to obtain 3D reconstructions. We identified anatomical conditions (ACs) according to the extent of the effect on the bony screw pathway. Subsequently, the pelvis was spatially aligned using representative bone protuberances in order to create standard Matta projections. In each view, the ACs were described in terms of distance from bone landmarks. Three-dimensional shape analysis revealed the height of the pedicular isthmus (PH) as the limiting variable for secure screw insertion. The lateral and outlet views allowed an orthogonal projection of PH. In the lateral view, the ratio of the lateral sacral triangle framed by the S1 body height and width showed a high correlation to PH ( p = 0.0001). A boundary ratio of 1.5 represented a reliable variable to determine whether or not a screw can be inserted (positive predictive value: 97%). In the outlet view, the distance between the S1 endplate and the SI joint top level (EJ) strongly correlated with PH ( p = 0.0001). With EJ ≤ 0 mm, screw insertion was possible in all cases (100%). SI-screw insertion requires a well-planned procedure. Orientation of the sacral pedicle is of extreme relevance. A narrow sacroiliac channel and high sacral shape variability limit secure screw placement. However, no determining parameters exist, allowing accurate prediction of secure screw insertion based on X-rays or fluoroscopy. The lateral sacral triangle in the lateral view represents a simple and accurate preoperative method of support for the surgeon's decision to undertake this procedure. No additional technical effort is necessary. A boundary ratio of 1.5 predicts a sufficient bone stock for at least one 7.3 mm screw. Furthermore, the evaluation of the outlet projection can be used to assess the safety of the operation. Basically, a preoperative lateral pelvic image should be mandatory.
Abstract Sacroiliac (SI) screw fixation for unstable pelvic fractures stands out as the only minimally invasive method among all other ORIF procedures. A strictly transverse screw trajectory is ...needed for central or bilateral fracture patterns up to a complete iliosacroiliac fixation. However, secure screw insertion is aggravated by a narrow sacroiliac bone stock. This study investigates the influence of a highly variable sacral morphology to the existence of S1 and S2 transverse corridors. The analysis contained in this study is based on 125 CT datasets of intact human pelvises. First, sacral dysplasia was identified using the “lateral sacral triangle” method in a lateral 3-D semi-transparent pelvic view. Second, 3-D corridors for a 7.3 mm screw in the upper two sacral levels were visualised using a proprietary IT workflow of custom-made programme scripts based on the Amira® -software. Shape-describing measurement variables were calculated as output variables. The results show a significant linear correlation between ratioT and the screw-limiting S1 isthmus height (Pearson coefficient of 0.84). A boundary ratio of 1.5 represented a positive predictive value of 96% for the existence of a transverse S1-corridor for at least one 7.3 mm screw. In 100 out of 125 pelvises (80%), a sufficient S1 corridor existed, whereas in 124 specimens (99%), an S2 corridor was found. Statistics revealed significantly larger S1 and S2 corridors in males compared to females ( p < 0.05). However, no gender-related differences were observed for clinically relevant numbers of up to 3 screws in S1 and 1 screw in S2. The expanse of the S1 corridor is highly influenced by the dimensions of the dysplastic elevated upper sacrum, whereas the S2 corridor is not affected. Hence, in dysplastic pelvises, sacroiliac screw insertion should be recommended into the 2nd sacral segment. Our IT workflow for the automatic computation of 3-D corridors may assist in surgical pre-operative planning. Furthermore, the workflow could be implemented in computer-assisted surgery applications involving pelvic trauma.
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