ABSTRACT
We exploit deep integral-field spectroscopic observations with KMOS/Very Large Telescope of 240 star-forming disks at
to dynamically constrain their mass budget. Our sample consists of ...massive (
) galaxies with sizes
. By contrasting the observed velocity and dispersion profiles with dynamical models, we find that on average the stellar content contributes
of the total dynamical mass, with a significant spread among galaxies (68th percentile range
). Including molecular gas as inferred from CO- and dust-based scaling relations, the estimated baryonic mass adds up to
of the total for the typical galaxy in our sample, reaching
at
. We conclude that baryons make up most of the mass within the disk regions of high-redshift star-forming disk galaxies, with typical disks at
being strongly baryon-dominated within
R
e
. Substantial object-to-object variations in both stellar and baryonic mass fractions are observed among the galaxies in our sample, larger than what can be accounted for by the formal uncertainties in their respective measurements. In both cases, the mass fractions correlate most strongly with measures of surface density. High-
galaxies feature stellar mass fractions closer to unity, and systems with high inferred gas or baryonic surface densities leave less room for additional mass components other than stars and molecular gas. Our findings can be interpreted as more extended disks probing further (and more compact disks probing less far) into the dark matter halos that host them.
We exploit the deep, resolved, H kinematic data from the KMOS3D and SINS/zC-SINF surveys to examine the largely unexplored outer-disk kinematics of star-forming galaxies (SFGs), out to the peak of ...cosmic star formation. Our sample contains 101 SFGs, representative of the more massive ( ) main sequence population at 0.6 ≤ z ≤ 2.6. Through a novel stacking approach, we are able to constrain a representative rotation curve extending out to ∼4 effective radii. This average rotation curve exhibits a significant drop in rotation velocity beyond the turnover, with a slope of in units of normalized coordinates V/Vmax and R/Rturn. This result confirms that the fall-off seen in some individual galaxies is a common feature of our sample of high-z disks. The outer fall-off strikingly deviates from the flat or mildly rising rotation curves of local spiral galaxies that have similar masses. Through a comparison with models that include baryons and dark matter, we demonstrate that the falling stacked rotation curve is consistent with a high mass fraction of baryons, relative to the total dark matter halo (md 0.05), in combination with a sizeable level of pressure support in the outer disk. These findings agree with recent studies demonstrating that high-z star-forming disks are strongly baryon-dominated within the disk scale, and furthermore suggest that pressure gradients caused by large, turbulent gas motions are present even in their outer disks. These results are largely independent of our model assumptions, such as the presence of stellar bulges, the effect of adiabatic contraction, and variations in halo concentration.
We present measurements of the N ii/Hα ratio as a probe of gas-phase oxygen abundance for a sample of 419 star-forming galaxies at z = 0.6–2.7 from the KMOS{sup 3D} near-IR multi-integral field unit ...(IFU) survey. The mass–metallicity relation (MZR) is determined consistently with the same sample selection, metallicity tracer, and methodology over the wide redshift range probed by the survey. We find good agreement with long-slit surveys in the literature, except for the low-mass slope of the relation at z∼2.3, where this sample is less biased than previous samples based on optical spectroscopic redshifts. In this regime we measure a steeper slope than some literature results. Excluding the contribution from active galactic nuclei from the MZR reduces sensitivity at the high-mass end, but produces otherwise consistent results. There is no significant dependence of the N ii/Hα ratio on star formation rate at fixed redshift and stellar mass. The IFU data allow spatially resolved measurements of N ii/Hα, from which we can infer abundance gradients for 180 galaxies, thus tripling the current sample in the literature. The observed gradients are on average flat, with only 15 gradients statistically offset from zero at >3σ. We have modeled the effect of beam smearing, assuming a smooth intrinsic radial gradient and known seeing, inclination, and effective radius for each galaxy. Our seeing-limited observations can recover up to 70% of the intrinsic gradient for the largest, face-on disks, but only 30% for the smaller, more inclined galaxies. We do not find significant trends between observed or corrected gradients and any stellar population, dynamical, or structural galaxy parameters, mostly in agreement with existing studies with much smaller sample sizes. In cosmological simulations, strong feedback is generally required to produce flat gradients at high redshift.
We exploit the deep, resolved, Hα kinematic data from the KMOS{sup 3D} and SINS/zC-SINF surveys to examine the largely unexplored outer-disk kinematics of star-forming galaxies (SFGs), out to the ...peak of cosmic star formation. Our sample contains 101 SFGs, representative of the more massive (9.3≲logM{sub ∗}/M{sub ⊙}≲11.5) main sequence population at 0.6 ≤ z ≤ 2.6. Through a novel stacking approach, we are able to constrain a representative rotation curve extending out to ∼4 effective radii. This average rotation curve exhibits a significant drop in rotation velocity beyond the turnover, with a slope of ΔV/ΔR=−0.26{sub −0.09}{sup +0.10} in units of normalized coordinates V/V {sub max} and R/R {sub turn}. This result confirms that the fall-off seen in some individual galaxies is a common feature of our sample of high-z disks. The outer fall-off strikingly deviates from the flat or mildly rising rotation curves of local spiral galaxies that have similar masses. Through a comparison with models that include baryons and dark matter, we demonstrate that the falling stacked rotation curve is consistent with a high mass fraction of baryons, relative to the total dark matter halo (m {sub d} ≳ 0.05), in combination with a sizeable level of pressure support in the outer disk. These findings agree with recent studies demonstrating that high-z star-forming disks are strongly baryon-dominated within the disk scale, and furthermore suggest that pressure gradients caused by large, turbulent gas motions are present even in their outer disks. These results are largely independent of our model assumptions, such as the presence of stellar bulges, the effect of adiabatic contraction, and variations in halo concentration.
ABSTRACT We present measurements of the N ii/H ratio as a probe of gas-phase oxygen abundance for a sample of 419 star-forming galaxies at z = 0.6-2.7 from the KMOS3D near-IR multi-integral field ...unit (IFU) survey. The mass-metallicity relation (MZR) is determined consistently with the same sample selection, metallicity tracer, and methodology over the wide redshift range probed by the survey. We find good agreement with long-slit surveys in the literature, except for the low-mass slope of the relation at , where this sample is less biased than previous samples based on optical spectroscopic redshifts. In this regime we measure a steeper slope than some literature results. Excluding the contribution from active galactic nuclei from the MZR reduces sensitivity at the high-mass end, but produces otherwise consistent results. There is no significant dependence of the N ii/H ratio on star formation rate at fixed redshift and stellar mass. The IFU data allow spatially resolved measurements of N ii/H , from which we can infer abundance gradients for 180 galaxies, thus tripling the current sample in the literature. The observed gradients are on average flat, with only 15 gradients statistically offset from zero at . We have modeled the effect of beam smearing, assuming a smooth intrinsic radial gradient and known seeing, inclination, and effective radius for each galaxy. Our seeing-limited observations can recover up to 70% of the intrinsic gradient for the largest, face-on disks, but only 30% for the smaller, more inclined galaxies. We do not find significant trends between observed or corrected gradients and any stellar population, dynamical, or structural galaxy parameters, mostly in agreement with existing studies with much smaller sample sizes. In cosmological simulations, strong feedback is generally required to produce flat gradients at high redshift.
Abstract
We exploit the deep, resolved, H
α
kinematic data from the KMOS
3D
and SINS/zC-SINF surveys to examine the largely unexplored outer-disk kinematics of star-forming galaxies (SFGs), out to ...the peak of cosmic star formation. Our sample contains 101 SFGs, representative of the more massive (
) main sequence population at 0.6 ≤
z
≤ 2.6. Through a novel stacking approach, we are able to constrain a representative rotation curve extending out to ∼4 effective radii. This average rotation curve exhibits a significant drop in rotation velocity beyond the turnover, with a slope of
in units of normalized coordinates
V
/
V
max
and
R
/
R
turn
. This result confirms that the fall-off seen in some individual galaxies is a common feature of our sample of high-
z
disks. The outer fall-off strikingly deviates from the flat or mildly rising rotation curves of local spiral galaxies that have similar masses. Through a comparison with models that include baryons and dark matter, we demonstrate that the falling stacked rotation curve is consistent with a high mass fraction of baryons, relative to the total dark matter halo (
m
d
≳ 0.05), in combination with a sizeable level of pressure support in the outer disk. These findings agree with recent studies demonstrating that high-
z
star-forming disks are strongly baryon-dominated within the disk scale, and furthermore suggest that pressure gradients caused by large, turbulent gas motions are present even in their outer disks. These results are largely independent of our model assumptions, such as the presence of stellar bulges, the effect of adiabatic contraction, and variations in halo concentration.
ABSTRACT We exploit deep integral-field spectroscopic observations with KMOS/Very Large Telescope of 240 star-forming disks at to dynamically constrain their mass budget. Our sample consists of ...massive ( ) galaxies with sizes . By contrasting the observed velocity and dispersion profiles with dynamical models, we find that on average the stellar content contributes of the total dynamical mass, with a significant spread among galaxies (68th percentile range ). Including molecular gas as inferred from CO- and dust-based scaling relations, the estimated baryonic mass adds up to of the total for the typical galaxy in our sample, reaching at . We conclude that baryons make up most of the mass within the disk regions of high-redshift star-forming disk galaxies, with typical disks at being strongly baryon-dominated within Re. Substantial object-to-object variations in both stellar and baryonic mass fractions are observed among the galaxies in our sample, larger than what can be accounted for by the formal uncertainties in their respective measurements. In both cases, the mass fractions correlate most strongly with measures of surface density. High- galaxies feature stellar mass fractions closer to unity, and systems with high inferred gas or baryonic surface densities leave less room for additional mass components other than stars and molecular gas. Our findings can be interpreted as more extended disks probing further (and more compact disks probing less far) into the dark matter halos that host them.
ABSTRACT
We present measurements of the N
ii
/H
α
ratio as a probe of gas-phase oxygen abundance for a sample of 419 star-forming galaxies at
z
= 0.6–2.7 from the KMOS
3D
near-IR multi-integral ...field unit (IFU) survey. The mass–metallicity relation (MZR) is determined consistently with the same sample selection, metallicity tracer, and methodology over the wide redshift range probed by the survey. We find good agreement with long-slit surveys in the literature, except for the low-mass slope of the relation at
, where this sample is less biased than previous samples based on optical spectroscopic redshifts. In this regime we measure a steeper slope than some literature results. Excluding the contribution from active galactic nuclei from the MZR reduces sensitivity at the high-mass end, but produces otherwise consistent results. There is no significant dependence of the N
ii
/H
α
ratio on star formation rate at fixed redshift and stellar mass. The IFU data allow spatially resolved measurements of N
ii
/H
α
, from which we can infer abundance gradients for 180 galaxies, thus tripling the current sample in the literature. The observed gradients are on average flat, with only 15 gradients statistically offset from zero at
. We have modeled the effect of beam smearing, assuming a smooth intrinsic radial gradient and known seeing, inclination, and effective radius for each galaxy. Our seeing-limited observations can recover up to 70% of the intrinsic gradient for the largest, face-on disks, but only 30% for the smaller, more inclined galaxies. We do not find significant trends between observed or corrected gradients and any stellar population, dynamical, or structural galaxy parameters, mostly in agreement with existing studies with much smaller sample sizes. In cosmological simulations, strong feedback is generally required to produce flat gradients at high redshift.
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