The Stellar, Gas and Dynamical Masses of Star-Forming Galaxies at z~2 (original) (raw)
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Comparing dynamical and photometric-stellar masses of early-type galaxies at z ~ 1
Astronomy and Astrophysics, 2006
Aims. The purpose of this study is to explore the relationship between galaxy stellar masses, based on multiwavelength photometry spectral template fitting and dynamical masses based on published velocity dispersion measurements, for a sample of 48 early-type galaxies at z ∼ 1 with HST/ACS morphological information. Methods. We determine photometric-stellar masses and perform a quantitative morphological analysis of cluster and field galaxies at redshift 0.6 < z < 1.2, using ground-and space-based multiwavelength data available on the GOODS-S field and on the field around the X-ray luminous cluster RDCS1252.9-2927 at z = 1.24. We use multi-band photometry over 0.4-8 µm from HST/ACS, VLT/ISAAC and Spitzer/IRAC to estimate photometric-stellar masses using Composite Stellar Population (CSP) templates computed with PEGASE.2 (Fioc & Rocca-Volmerange 1997) models. We compare stellar masses with those obtained using CSPs built with
COMPLEX GAS KINEMATICS IN COMPACT, RAPIDLY ASSEMBLING STAR-FORMING GALAXIES
Deep, high-resolution spectroscopic observations have been obtained for six compact, strongly star-forming galaxies at redshift z ∼ 0.1–0.3, most of them also known as green peas. Remarkably, these galaxies show complex emission-line profiles in the spectral region including Hα, [N ii] λλ6548, 6584, and [S ii] λλ6717, 6731, consisting of the superposition of different kinematical components on a spatial extent of few kiloparsecs: a very broad line emission underlying more than one narrower component. For at least two of the observed galaxies some of these multiple components are resolved spatially in their two-dimensional spectra, whereas for another one a faint detached Hα blob lacking stellar continuum is detected at the same recessional velocity ∼7 kpc away from the galaxy. The individual narrower Hα components show high intrinsic velocity dispersion (σ ∼ 30–80 km s −1), suggesting together with unsharped masking Hubble Space Telescope images that star formation proceeds in an ensemble of several compact and turbulent clumps, with relative velocities of up to ∼500 km s −1. The broad underlying Hα components indicate in all cases large expansion velocities (full width zero intensity 1000 km s −1) and very high luminosities (up to ∼10 42 erg s −1), probably showing the imprint of energetic outflows from supernovae. These intriguing results underline the importance of green peas for studying the assembly of low-mass galaxies near and far.
Astrophysical Journal, 2004
We recently identified a substantial population of galaxies at z>2 with red rest-frame optical colors. These distant red galaxies (DRGs) are efficiently selected by the simple observed color criterion J-K>2.3. In this paper we present NIR spectroscopy with Keck/NIRSPEC of six DRGs at 2.4<z<3.2. We detect continuum emission and emission lines of all observed galaxies. Equivalent widths of H alpha are 20-30 Ang, smaller than measured for LBGs and nearby LIRGs, and comparable to normal nearby galaxies. The modest equivalent widths imply that the galaxies either have a decreasing star formation rate, or that they are very dusty. Fitting both the photometry and the H alpha lines, we find continuum extinction A_V=1-2 mag, ages 1-2.5 Gyr, star formation rates 200-400 solar masses/yr, and stellar masses 1-5x10^11 solar masses for models with constant star formation rates. From [NII]/H alpha ratios we infer that the metallicities are high, 1-1.5 x Solar. For four galaxies we can determine line widths from the optical emission lines. The widths are high, ranging from 130-240 km/s, and by combining data for LBGs and DRGs we find significant correlations between linewidth and restframe U-V color, and between linewidth and stellar mass. The latter correlation has a similar slope and offset as the ``baryonic Tully-Fisher relation'' for nearby galaxies. The median dynamical mass is ~2x10^11 solar masses, supporting the high stellar masses inferred from the photometry. We find that the median M/L_V ~ 0.8, a factor of ~5 higher than measured for LBGs. We infer from our small sample that DRGs are dustier, more metal rich, more massive, and have higher ages than z=3 LBGs of the same rest-frame V-band luminosity. Their high M/L ratios imply that they contribute significantly to the stellar mass density at z~2.5. [ABRIDGED]
The Astrophysical Journal, 2011
We present Gran-Telescopio-Canarias/OSIRIS optical spectra of 4 of the most compact and massive early-type galaxies in the Groth Strip Survey at redshift z ∼ 1, with effective radii R e = 0.5 − 2.4 kpc and photometric stellar masses M ⋆ = 1.2 − 4 × 10 11 M ⊙ . We find these galaxies have velocity dispersions σ = 156 − 236 km s −1 . The spectra are well fitted by single stellar population models with approximately 1 Gyr of age and solar metallicity. We find that: i) the dynamical masses of these galaxies are systematically smaller by a factor of ∼6 than the published stellar masses using BRIJK photometry; ii) when estimating stellar masses as 0.7×M dyn , a combination of passive luminosity fading with mass/size growth due to minor mergers can plausibly evolve our objects to match the properties of the local population of early-type galaxies.
Fingerprints of the hierarchical building-up of the structure on the gas kinematics of galaxies
Astronomy & Astrophysics, 2012
Context. Recent observational and theoretical works have suggested that the Tully-Fisher Relation might be generalised to include dispersion-dominated systems by combining the rotation and dispersion velocity in the definition of the kinematical indicator. Mergers and interactions have been pointed out as responsible of driving turbulent and disordered gas kinematics, which could generate Tully-Fisher Relation outliers. Aims. We intend to investigate the gas kinematics of galaxies by using a simulated sample which includes both, gas disc-dominated and spheroid-dominated systems. We pay particular attention to the evolution of the scatter of the Tully-Fisher Relation. We also aim at determining the gas-phase velocity indicator which better traces the potential well of the galaxy. Methods. Cosmological hydrodynamical simulations which include a multiphase model and physically-motivated Supernova feedback were performed in order to follow the evolution of galaxies as they are assembled. We analyse the gas kinematics of the surviving gas discs to estimate all velocity indicators. Results. Both the baryonic and stellar Tully-Fisher relations for gas disc-dominated systems are tight while, as more dispersion-dominated systems are included, the scatter increases. We found a clear correlation between σ/Vrot and morphology, with dispersion-dominated systems exhibiting the larger values (> 0.7). Mergers and interactions can affect the rotation curves directly or indirectly inducing a scatter in the Tully-Fisher Relation larger than the simulated evolution since z ∼ 3. Kinematical indicators which combine rotation velocity and dispersion velocity can reduce the scatter in the baryonic and the stellar mass-velocity relations. In particular, s1.0 = (V 2 rot + σ 2) 0.5 seems to be the best tracer of the circular velocity at larger radii. Our findings also show that the lowest scatter in both relations is obtained if the velocity indicators are measured at the maximum of the rotation curve. Conclusions. In agreement with previous works, we found that the gas kinematics of galaxies is significantly regulated by mergers and interactions, which play a key role in inducing gas accretion, outflows and starbursts. The joint action of these processes within a hierarchical ΛCDM Universe generates a mean simulated Tully-Fisher Relation in good agreement with observations since z ∼ 3 but with a scatter depending on morphology. The rotation velocity estimated at the maximum of the gas rotation curve is found to be the best proxy for the potential well regardless of morphology.
Astronomy and Astrophysics, 2008
Measuring the build-up of stellar mass is one of the main objectives of studies of galaxy evolution. Traditionally, the mass in stars and the star formation rates have been measured by different indicators, such as photometric colours, emission lines, and the UV and IR emission. We intend to show that it is possible to derive the physical parameters of galaxies from their broad-band spectral energy distribution out to a redshift of 1.2. This method has the potential to yield the physical parameters of all galaxies in a single field in a homogeneous way, thus overcoming problems with the sample size that particularly plague methods relying on spectroscopy. We use an extensive dataset, assembled in the context of the VVDS survey, which reaches from the UV to the IR and covers a sample of 84073 galaxies over an area of 0.89 deg 2 . We also use a library of 100000 model galaxies with a wide variety of star formation histories (in particular including late bursts of star formation). We find that we can determine the physical parameters stellar mass, age, and star formation rate with good confidence. We validate the star formation rate determination in particular by comparing it to a sample of spectroscopically observed galaxies with an emission-line measurement. While the attenuation in the galaxies shows more scatter, the mean over the sample is unbiased. Metallicity, however, cannot be measured from rest-frame optical photometry alone. As a first application we use our sample to build the number density function of galaxies as a function of stellar mass, specific star formation rate, and redshift. We are then able to study whether the stellar mass function at a later time can be predicted from the stellar mass function and star formation rate distribution at an earlier time. We find that, between redshifts of 1.02 and 0.47, the predicted growth in stellar mass from star formation agrees with the observed one. However, the predicted stellar mass density for massive galaxies is lower than observed, while the mass density of intermediate mass galaxies is overpredicted. This apparent discrepancy can be explained by major and minor mergers. Indeed, when comparing with a direct measurement of the major merger rate from the VVDS survey, we find that major mergers can account for about half of the mass build-up at the massive end. Minor mergers are very likely to contribute the missing fraction.
Monthly Notices of the Royal Astronomical Society, 2014
We present an investigation about the shape of the initial mass function (IMF) of early-type galaxies (ETGs), based on a joint lensing and dynamical analysis, and on stellar population synthesis models, for a sample of 55 lens ETGs identified by the Sloan Lens ACS (SLACS) Survey. We construct axisymmetric dynamical models based on the Jeans equations which allow for orbital anisotropy and include a dark matter halo. The models reproduce in detail the observed HST photometry and are constrained by the total projected mass within the Einstein radius and the stellar velocity dispersion (σ) within the SDSS fibers. Comparing the dynamically-derived stellar mass-to-light ratios (M * /L) dyn , obtained for an assumed halo slope ρ h ∝ r −1 , to the stellar population ones (M * /L) Salp , derived from full-spectrum fitting and assuming a Salpeter IMF, we infer the mass normalization of the IMF. Our results confirm the previous analysis by the SLACS team that the mass normalization of the IMF of high σ galaxies is consistent on average with a Salpeter slope. Our study allows for a fully consistent study of the trend between IMF and σ for both the SLACS and ATLAS 3D samples, which explore quite different σ ranges. The two samples are highly complementary, the first being essentially σ selected, and the latter volume-limited and nearly mass selected. We find that the two samples merge smoothly into a single trend of the form log α = (0.38 ± 0.04) × log(σ e /200 km s −1) + (−0.06 ± 0.01), where α = (M * /L) dyn /(M * /L) Salp and σ e is the luminosity averaged σ within one effective radius R e. This is consistent with a systematic variation of the IMF normalization from Kroupa to Salpeter in the interval σ e ≈ 90 − 270 km s −1 .
The Astrophysical Journal, 2010
We use stellar masses, surface photometry, strong lensing masses, and stellar velocity dispersions (σ e/2) to investigate empirical correlations for the definitive sample of 73 early-type galaxies (ETGs) that are strong gravitational lenses from the SLACS survey. The traditional correlations (Fundamental Plane [FP] and its projections) are consistent with those found for non-lens galaxies, supporting the thesis that SLACS lens galaxies are representative of massive ETGs (dimensional mass M dim = 10 11 − 10 12 M ⊙). The addition of high-precision strong lensing estimates of the total mass allows us to gain further insights into their internal structure: i) the average slope of the total mass density profile (ρ tot ∝ r −γ ′) is γ ′ = 2.078 ± 0.027 with an intrinsic scatter of 0.16 ± 0.02; ii) γ ′ correlates with effective radius (r e) and central mass density, in the sense that denser galaxies have steeper profiles; iii) the dark matter fraction within r e /2 is a monotonically increasing function of galaxy mass and size (due to a mass-dependent central cold dark matter distribution or to baryonic dark matter-stellar remnants or low mass stars-if the IMF is non-universal and its normalization increases with mass); iv) the dimensional mass M dim ≡ 5r e σ 2 e/2 /G is proportional to the total (lensing) mass M re/2 , and both increase more rapidly than stellar mass M * (M * ∝ M 0.8 re/2); v) the Mass Plane (MP), obtained by replacing surface brightness with surface mass density in the FP, is found to be tighter and closer to the virial relation than the FP and the M * P, indicating that the scatter of those relations is dominated by stellar populations effects; vi) we construct the Fundamental Hyper-Plane by adding stellar masses to the MP and find the M * coefficient to be consistent with zero and no residual intrinsic scatter. Our results demonstrate that the dynamical structure of ETGs is not scale invariant and that it is fully specified by M re/2 , r e , and σ e/2. Although the basic trends can be explained qualitatively in terms of varying star formation efficiency as a function of halo mass and as the result of dry and wet mergers, reproducing quantitatively the observed correlations and their tightness may be a significant challenge for galaxy formation models.
The star formation reference survey – IV. Stellar mass distribution of local star-forming galaxies
Monthly Notices of the Royal Astronomical Society, 2021
We constrain the mass distribution in nearby, star-forming galaxies with the Star Formation Reference Survey (SFRS), a galaxy sample constructed to be representative of all known combinations of star formation rate (SFR), dust temperature, and specific star formation rate (sSFR) that exist in the Local Universe. An innovative two-dimensional bulge/disk decomposition of the 2MASS/-band images of the SFRS galaxies yields global luminosity and stellar mass functions, along with separate mass functions for their bulges and disks. These accurate mass functions cover the full range from dwarf galaxies to large spirals, and are representative of star-forming galaxies selected based on their infra-red luminosity, unbiased by AGN content and environment. We measure an integrated luminosity density = 1.72 ± 0.93 × 10 9 L ℎ −1 Mpc −3 and a total stellar mass density = 4.61 ± 2.40 × 10 8 M ℎ −1 Mpc −3. While the stellar mass of the average star-forming galaxy is equally distributed between its sub-components, disks globally dominate the mass density budget by a ratio 4:1 with respect to bulges. In particular, our functions suggest that recent star formation happened primarily in massive systems, where they have yielded a disk stellar mass density larger than that of bulges by more than 1 dex. Our results constitute a reference benchmark for models addressing the assembly of stellar mass on the bulges and disks of local (= 0) star-forming galaxies.
The Astrophysical Journal, 2005
The kinematic properties of the gaseous and stellar components of 11 ultraluminous infrared galaxies ( ULIRGs; 14 nuclei) are investigated by means of integral field spectroscopy ( IFS) with the INTEGRAL system and available IR and CO millimeter spectroscopy. The sample of ULIRGs cover different phases of the merging process and span all levels of activity from pure starbursts to Seyfert nuclei. The IFS data show that the ionized gas has a complex velocity structure with peak-to-peak velocity differences of a few to several hundred km s À1 , detected in tidal tails or extranuclear star-forming regions. The velocity field of the ionized gas on scales of a few to several kiloparsecs is dominated by tidally induced flows and does not, in general, correspond to rotationally supported systems with a privileged orientation along the major rotating axis. The central velocity amplitude of the ionized gas and stars shows discrepancies in some galaxies but has, on average, a similar value (ratio of 0:92 AE 0:37) , while the velocity amplitude of the molecular gas is a factor of 2 larger (ratio of 1:9 AE 0:6) than that of the stars and ionized gas. The central velocity amplitude measured using different kinematic tracers should therefore not be used in ULIRGs as a reliable tracer of mass, in general. The IFS data also show that the velocity dispersion of the ionized gas maps the large-scale motions associated with tidal tails and extranuclear regions, with often the highest velocity dispersion not being associated with the nucleus galaxies. There is, however, a good agreement between the central ionized gas and stellar velocity dispersions (ratio of 1:01 AE 0:13), while the cold molecular gas velocity dispersion has lower values (average of about 0.8 that of the stellar and ionized gas). The central ionized gas velocity dispersion is therefore a robust and homogeneous observable and a good tracer of the dynamical mass in these systems. The IFSbased central ionized gas velocity dispersion measurements confirm that ULIRGs' hosts are moderate-mass ( m à ) galaxies, as previously concluded by Tacconi and coworkers. In general, velocity amplitudes should not be used to estimate the dynamical mass in high-z star-forming systems, such as Lyman break and in particular submillimeter galaxies, since they show irregular stellar and gaseous structures similar to those present in low-z merging systems such as ULIRGs, the subject of this study. A more reliable method is to measure the central velocity dispersion using the strong, high equivalent width, rest-frame optical emission lines, provided the location of the nucleus is independently established by high angular resolution red or near-IR rest-frame imaging. The kinematics derived from the millimeter CO line suggest that the cold gas in ULIRGs does not share the velocity field of the stars and ionized gas and seems to be more rotationally supported. This result needs to be investigated in more detail with a larger sample of low-z ULIRGs before using the millimeter CO line widths as a dynamical mass tracer in high-z submillimeter galaxies.