Using SINFONI Halpha, NII, and SII AO data of 27 z ~ 2 star-forming galaxies (SFGs) from the SINS and zC-SINF surveys, we explore the dependence of outflow strength (via the broad flux fraction) on ...various galaxy parameters. For galaxies that have evidence for strong outflows, we find that the broad emission is spatially extended to at least the half-light radius (~a few kpc). Decomposition of the SII doublet into broad and narrow components suggests that this outflowing gas probably has a density of ~10-100 cm super(-3), less than that of the star-forming gas (600 cm super(-3)). There is a strong correlation of the Halpha broad flux fraction with the star formation surface density of the galaxy, with an apparent threshold for strong outflows occurring at 1 M sub(middot in circle) yr super(-1) kpc super(-2). Above this threshold, we find that SFGs with log m sub(*) > 10 have similar or perhaps greater wind mass-loading factors (eta = M sub(out)/SFR) and faster outflow velocities than lower mass SFGs, suggesting that the majority of outflowing gas at z ~ 2 may derive from high-mass SFGs. The mass-loading factor is also correlated with the star formation rate (SFR), galaxy size, and inclination, such that smaller, more star-forming, and face-on galaxies launch more powerful outflows. We propose that the observed threshold for strong outflows and the observed mass loading of these winds can be explained by a simple model wherein break-out of winds is governed by pressure balance in the disk.
The zCOSMOS 10k-Bright Spectroscopic Sample Lilly, Simon J; Le Brun, Vincent; Maier, Christian ...
The Astrophysical journal. Supplement series,
10/2009, Letnik:
184, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present spectroscopic redshifts of a large sample of galaxies with I AB < 22.5 in the COSMOS field, measured from spectra of 10,644 objects that have been obtained in the first two years of ...observations in the zCOSMOS-bright redshift survey. These include a statistically complete subset of 10,109 objects. The average accuracy of individual redshifts is 110 km s-1, independent of redshift. The reliability of individual redshifts is described by a Confidence Class that has been empirically calibrated through repeat spectroscopic observations of over 600 galaxies. There is very good agreement between spectroscopic and photometric redshifts for the most secure Confidence Classes. For the less secure Confidence Classes, there is a good correspondence between the fraction of objects with a consistent photometric redshift and the spectroscopic repeatability, suggesting that the photometric redshifts can be used to indicate which of the less secure spectroscopic redshifts are likely right and which are probably wrong, and to give an indication of the nature of objects for which we failed to determine a redshift. Using this approach, we can construct a spectroscopic sample that is 99% reliable and which is 88% complete in the sample as a whole, and 95% complete in the redshift range 0.5 < z < 0.8. The luminosity and mass completeness levels of the zCOSMOS-bright sample of galaxies is also discussed.
We present the first observations of foreground Lyα forest absorption from high-redshift galaxies, targeting 24 star-forming galaxies (SFGs) with z ~ 2.3-2.8 within a 5' × 14' region of the COSMOS ...field. The transverse sightline separation is ~2 h-1 Mpc comoving, allowing us to create a tomographic reconstruction of the three-dimensional (3D) Lyα forest absorption field over the redshift range 2.20 ≤ z ≤ 2.45. The resulting map covers 6 h-1 Mpc × 14 h-1 Mpc in the transverse plane and 230 h-1 Mpc along the line of sight with a spatial resolution of ≈3.5 h-1 Mpc, and is the first high-fidelity map of a large-scale structure on ~ Mpc scales at z > 2. Our map reveals significant structures with ≳10 h-1 Mpc extent, including several spanning the entire transverse breadth, providing qualitative evidence for the filamentary structures predicted to exist in the high-redshift cosmic web. Simulated reconstructions with the same sightline sampling, spectral resolution, and signal-to-noise ratio recover the salient structures present in the underlying 3D absorption fields. Using data from other surveys, we identified 18 galaxies with known redshifts coeval with our map volume, enabling a direct comparison with our tomographic map. This shows that galaxies preferentially occupy high-density regions, in qualitative agreement with the same comparison applied to simulations. Our results establish the feasibility of the CLAMATO survey, which aims to obtain Lyα forest spectra for ~1000 SFGs over ~1 deg2 of the COSMOS field, in order to map out the intergalactic medium large-scale structure at 〈z〉 ~ 2.3 over a large volume (100 h-1 Mpc)3.
We analyze the spectra, spatial distributions, and kinematics of H alpha , NII, and SII emission in a sample of 38, z ~ 2.2 UV/optically selected star-forming galaxies (SFGs) from the SINS and ...zC-SINF surveys, 34 of which were observed in the adaptive optics mode of SINFONI and 30 of those contain data presented for the first time here. This is supplemented by kinematic data from 43 z ~ 1-2.5 galaxies from the literature. None of these 81 galaxies is an obvious major merger. We find that the kinematic classification of high-z SFGs as "dispersion dominated" or "rotation dominated" correlates most strongly with their intrinsic sizes. Smaller galaxies are more likely "dispersion-dominated" for two main reasons: (1) the rotation velocity scales linearly with galaxy size but intrinsic velocity dispersion does not depend on size or may even increase in smaller galaxies, and as such, their ratio is systematically lower for smaller galaxies, and (2) beam smearing strongly decreases large-scale velocity gradients and increases observed dispersion much more for galaxies with sizes at or below the resolution. Dispersion-dominated SFGs may thus have intrinsic properties similar to "rotation-dominated" SFGs, but are primarily more compact, lower mass, less metal enriched, and may have higher gas fractions, plausibly because they represent an earlier evolutionary state.
Abstract
The discovery and spectroscopic confirmation of Hyperion, a protosupercluster at
z
∼ 2.47, provides an unprecedented opportunity to study distant galaxies in the context of their large-scale ...environment. We carry out deep narrowband imaging of a ≈1° × 1° region around Hyperion and select 157 Ly
α
emitters (LAEs). The inferred LAE overdensity is
δ
g
≈ 40 within an effective volume of 30 × 20 × 15 cMpc
3
, consistent with the fact that Hyperion is composed of multiple protoclusters and will evolve into a supercluster with a total mass of
M
tot
≈ 1.4 × 10
15
M
⊙
at
z
= 0. The distribution of LAEs closely mirrors that of known spectroscopic members, tracing the protocluster cores and extended filamentary arms connected to them, suggesting that they trace the same large-scale structure. By cross-correlating the LAE positions with H
i
tomography data, we find weak evidence that LAEs may be less abundant in the highest H
i
regions, perhaps because Ly
α
is suppressed in such regions. The Hyperion region hosts a large population of active galactic nuclei (AGNs) ≈ 12 times more abundant than that in the field. The prevalence of AGNs in protocluster regions hints at the possibility that they may be triggered by physical processes that occur more frequently in dense environments, such as galaxy mergers. Our study demonstrates LAEs as reliable markers of the largest cosmic structures. When combined with ongoing and upcoming imaging and spectroscopic surveys, wide-field narrowband imaging has the potential to advance our knowledge in the formation and evolution of cosmic structures and of their galaxy inhabitants.
Based on high-resolution, spatially resolved data of 10 z ~ 2 star-forming galaxies from the SINS/zC-SINF survey and LUCI data for 12 additional galaxies, we probe the excitation properties of high-z ...galaxies and the impact of active galactic nuclei (AGNs), shocks, and photoionization. We explore how these spatially resolved line ratios can inform our interpretation of integrated emission line ratios obtained at high redshift. Many of our galaxies fall in the "composite" region of the z ~ 0 NII/H alpha versus OIII/H beta diagnostic (BPT) diagram, between star-forming galaxies and those with AGNs. Based on our resolved measurements, we find that some of these galaxies likely host an AGN, while others appear to be affected by the presence of shocks possibly caused by an outflow or from an enhanced ionization parameter as compared with Hu regions in normal, local star-forming galaxies. We find that the Mass-Excitation (MEx) diagnostic, which separates purely star-forming and AGN hosting local galaxies in the O sub(III)/H beta versus stellar mass plane, does not properly separate z ~ 2 galaxies classified according to the BPT diagram. However, if we shift the galaxies based on the offset between the local and z ~ 2 mass-metallicity relation (i.e., to the mass they would have at z ~ 0 with the same metallicity), we find better agreement between the MEx and BPT diagnostics. Finally, we find that metallicity calibrations based on NII/H alpha are more biased by shocks and AGNs at high-z than the OIII/H beta /NII/H alpha calibration.
Abstract
We present the radio properties of 66 spectroscopically confirmed normal star-forming galaxies (SFGs) at 4.4 <
z
< 5.9 in the COSMOS field that were C
ii
-detected in the Atacama Large ...Millimeter/submillimeter Array Large Program to INvestigate C
ii
at Early times (ALPINE). We separate these galaxies (“C
ii
-detected-all”) into lower-redshift (“C
ii
-detected-lz”; 〈
z
〉 = 4.5) and higher-redshift (“C
ii
-detected-hz”; 〈
z
〉 = 5.6) subsamples, and stack multiwavelength imaging for each subsample from X-ray to radio bands. A radio signal is detected in the stacked 3 GHz images of the C
ii
-detected-all and lz samples at ≳3
σ
. We find that the infrared–radio correlation of our sample, quantified by
q
TIR
, is lower than the local relation for normal SFGs at a ∼3
σ
significance level, and is instead broadly consistent with that of bright submillimeter galaxies at 2 <
z
< 5. Neither of these samples show evidence of dominant active galactic nucleus activity in their stacked spectral energy distributions (SEDs), UV spectra, or stacked X-ray images. Although we cannot rule out the possible effects of the assumed spectral index and applied infrared SED templates in causing these differences, at least partially, the lower obscured fraction of star formation than at lower redshift can alleviate the tension between our stacked
q
TIR
s and those of local normal SFGs. It is possible that the dust buildup, which primarily governs the infrared emission, in addition to older stellar populations, has not had enough time to occur fully in these galaxies, whereas the radio emission can respond on a more rapid timescale. Therefore, we might expect a lower
q
TIR
to be a general property of high-redshift SFGs.
We present the first C II 158 μm luminosity function (LF) at z ∼ 5 from a sample of serendipitous lines detected in the ALMA Large Program to INvestigate C II at Early times (ALPINE). A study of the ...118 ALPINE pointings revealed several serendipitous lines. Based on their fidelity, we selected 14 lines for the final catalog. According to the redshift of their counterparts, we identified eight out of 14 detections as C II lines at z ∼ 5, along with two as CO transitions at lower redshifts. The remaining four lines have an elusive identification in the available catalogs and we considered them as C II candidates. We used the eight confirmed C II and the four C II candidates to build one of the first C II LFs at z ∼ 5. We found that 11 out of these 12 sources have a redshift very similar to that of the ALPINE target in the same pointing, suggesting the presence of overdensities around the targets. Therefore, we split the sample in two (a “clustered” and “field” subsample) according to their redshift separation and built two separate LFs. Our estimates suggest that there could be an evolution of the C II LF between z ∼ 5 and z ∼ 0. By converting the C II luminosity to the star-formation rate, we evaluated the cosmic star-formation rate density (SFRD) at z ∼ 5. The clustered sample results in a SFRD ∼10 times higher than previous measurements from UV–selected galaxies. On the other hand, from the field sample (likely representing the average galaxy population), we derived a SFRD ∼1.6 higher compared to current estimates from UV surveys but compatible within the errors. Because of the large uncertainties, observations of larger samples will be necessary to better constrain the SFRD at z ∼ 5. This study represents one of the first efforts aimed at characterizing the demography of C II emitters at z ∼ 5 using a mm selection of galaxies.
We define a quasar-galaxy mixing diagram using the slopes of their spectral energy distributions (SEDs) from 1 μm to 3000 Å and from 1 to 3 μm in the rest frame. The mixing diagram can easily ...distinguish among quasar-dominated, galaxy-dominated and reddening-dominated SED shapes. By studying the position of the 413 XMM-selected type 1 AGN in the wide-field 'Cosmic Evolution Survey' in the mixing diagram, we find that a combination of the Elvis et al. mean quasar SED with various contributions from galaxy emission and some dust reddening is remarkably effective in describing the SED shape from 0.3 to 3 μm for large ranges of redshift, luminosity, black hole mass and Eddington ratio of type 1 AGN. In particular, the location in the mixing diagram of the highest luminosity AGN is very close (within 1σ) to that of the Elvis et al. SED template. The mixing diagram can also be used to estimate the host galaxy fraction and reddening in quasar. We also show examples of some outliers which might be AGN in different evolutionary stages compared to the majority of AGN in the quasar-host galaxy co-evolution cycle.
Using moderate-resolution optical spectra from 58 background Lyman-break galaxies and quasars at z∼2.3--3 within a 11.′5 × 13.′5 area of the COSMOS field (∼1200 deg{sup −2} projected area density or ...∼2.4 h{sup −1} Mpc mean transverse separation), we reconstruct a 3D tomographic map of the foreground Lyα forest absorption at 2.2 < z < 2.5 with an effective smoothing scale of ϵ{sub 3D}≈2.5 h{sup −1} Mpc comoving. Comparing with 61 coeval galaxies with spectroscopic redshifts in the same volume, we find that the galaxy positions are clearly biased toward regions with enhanced intergalactic medium (IGM) absorption in the tomographic map. We find an extended IGM overdensity with deep absorption troughs at z = 2.45 associated with a recently discovered galaxy protocluster at the same redshift. Based on simulations matched to our data, we estimate the enclosed dark matter mass within this IGM overdensity to be M{sub dm}(z=2.45)=(1.1±0.6)×10{sup 14} h{sup −1}M{sub ⊙}, and argue based on this mass and absorption strength that it will form at least one z ∼ 0 galaxy cluster with M(z=0)=(3±1.5)×10{sup 14} h{sup −1}M{sub ⊙}, although its elongated nature suggests that it will likely collapse into two separate clusters. We also point out a compact overdensity of six MOSDEF galaxies at z = 2.30 within a r∼1 h{sup −1} Mpc radius and Δz ∼ 0.006, which does not appear to have a large associated IGM overdensity. These results demonstrate the potential of Lyα forest tomography on larger volumes to study galaxy properties as a function of environment, as well as revealing the large-scale IGM overdensities associated with protoclusters or other features of large-scale structure.
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![The ALPINE–ALMA [C II] survey](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-6361/small "The ALPINE–ALMA [C II] survey")
