DETECTION OF THE 158 μm [C II] TRANSITION AT z = 1.3: EVIDENCE FOR A GALAXY-WIDE STARBURST (original) (raw)
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Detection of the 158 micron [CII] Transition at z= 1.3: Evidence for a Galaxy-Wide Starburst
We report the detection of 158 µm [CII] fine-structure line emission from MIPS J142824.0+352619, a hyperluminous (L IR ∼ 10 13 L ⊙ ) starburst galaxy at z = 1.3. The line is bright, and corresponds to a fraction L [CII] /L FIR ≈ 2 × 10 −3 of the far-IR (FIR) continuum. The [CII], CO, and FIR continuum emission may be modeled as arising from photodissociation regions (PDRs) that have a characteristic gas density of n ∼ 10 4.2 cm −3 , and that are illuminated by a far-UV radiation field ∼10 3.2 times more intense than the local interstellar radiation field. The mass in these PDRs accounts for approximately half of the molecular gas mass in this galaxy. The L [CII] /L FIR ratio is higher than observed in local ULIRGs or in the few high-redshift QSOs detected in [CII], but the L [CII] /L FIR and L CO /L FIR ratios are similar to the values seen in nearby starburst galaxies. This suggests that MIPS J142824.0+352619 is a scaled-up version of a starburst nucleus, with the burst extended over several kiloparsecs.
DETECTION OF THE 158 μm [C II] TRANSITION AT z = 1.3: EVIDENCE FOR A GALAXY-WIDE STARBURST
The Astrophysical Journal, 2010
We report the detection of 158 μm [C ii] fine-structure line emission from MIPS J142824.0+352619, a hyperluminous (L IR ∼ 10 13 L ) starburst galaxy at z = 1.3. The line is bright, corresponding to a fraction L [C ii] /L FIR ≈ 2 × 10 −3 of the far-IR (FIR) continuum. The [C ii], CO, and FIR continuum emission may be modeled as arising from photodissociation regions (PDRs) that have a characteristic gas density of n ∼ 10 4.2 cm −3 , and that are illuminated by a far-UV radiation field ∼10 3.2 times more intense than the local interstellar radiation field. The mass in these PDRs accounts for approximately half of the molecular gas mass in this galaxy. The L [C ii] /L FIR ratio is higher than observed in local ultraluminous infrared galaxies or in the few high-redshift QSOs detected in [C ii], but the L [C ii] /L FIR and L CO /L FIR ratios are similar to the values seen in nearby starburst galaxies. This suggests that MIPS J142824.0+352619 is a scaled-up version of a starburst nucleus, with the burst extended over several kiloparsecs.
The Astrophysical Journal, 2010
We have detected the 158 μm [C ii] line from 12 galaxies at z ∼ 1-2. This is the first survey of this important star formation tracer at redshifts covering the epoch of maximum star formation in the universe and quadruples the number of reported high-z [C ii] detections. The line is very luminous, between <0.024% and 0.65% of the far-infrared (FIR) continuum luminosity of our sources, and arises from photodissociation regions on molecular cloud surfaces. An exception is PKS 0215+015, where half of the [C ii] emission could arise from X-ray-dominated regions near the central active galactic nucleus (AGN). The L [C ii] /L FIR ratio in our star formation-dominated systems is ∼8 times larger than that of our AGN-dominated systems. Therefore this ratio selects for star formationdominated systems. Furthermore, the L [C ii] /L FIR and L [C ii] /L (CO(1-0)) ratios in our star-forming galaxies and nearby starburst galaxies are the same, so that luminous star-forming galaxies at earlier epochs (z ∼ 1-2) appear to be scaled-up versions of local starbursts entailing kiloparsec-scale starbursts. Most of the FIR and [C ii] radiation from our AGN-dominated sample (excepting PKS 0215+015) also arises from kiloparsec-scale star formation, but with far-UV radiation fields ∼8 times more intense than in our star formation-dominated sample. We speculate that the onset of AGN activity stimulates large-scale star formation activity within AGN-dominated systems. This idea is supported by the relatively strong [O iii] line emission, indicating very young stars, that was recently observed in high-z composite AGN/starburst systems. Our results confirm the utility of the [C ii] line, and in particular, the L [C ii] /L (FIR) and L [C ii] /L CO(1-0) ratios as tracers of star formation in galaxies at high redshifts.
The Astrophysical Journal, 2010
We have detected the 158 μm [C ii] line from 12 galaxies at z ∼ 1-2. This is the first survey of this important star formation tracer at redshifts covering the epoch of maximum star formation in the universe and quadruples the number of reported high-z [C ii] detections. The line is very luminous, between <0.024% and 0.65% of the far-infrared (FIR) continuum luminosity of our sources, and arises from photodissociation regions on molecular cloud surfaces. An exception is PKS 0215+015, where half of the [C ii] emission could arise from X-ray-dominated regions near the central active galactic nucleus (AGN). The L [C ii] /L FIR ratio in our star formation-dominated systems is ∼8 times larger than that of our AGN-dominated systems. Therefore this ratio selects for star formationdominated systems. Furthermore, the L [C ii] /L FIR and L [C ii] /L (CO(1-0)) ratios in our star-forming galaxies and nearby starburst galaxies are the same, so that luminous star-forming galaxies at earlier epochs (z ∼ 1-2) appear to be scaled-up versions of local starbursts entailing kiloparsec-scale starbursts. Most of the FIR and [C ii] radiation from our AGN-dominated sample (excepting PKS 0215+015) also arises from kiloparsec-scale star formation, but with far-UV radiation fields ∼8 times more intense than in our star formation-dominated sample. We speculate that the onset of AGN activity stimulates large-scale star formation activity within AGN-dominated systems. This idea is supported by the relatively strong [O iii] line emission, indicating very young stars, that was recently observed in high-z composite AGN/starburst systems. Our results confirm the utility of the [C ii] line, and in particular, the L [C ii] /L (FIR) and L [C ii] /L CO(1-0) ratios as tracers of star formation in galaxies at high redshifts.
High resolution observations of a starburst at z = 0.223: resolved CO(1–0) structure
Astronomy and Astrophysics, 2006
We present the results of mapping the CO(1-0) emission of the z = 0.223 ultra-luminous starburst IRAS 11582+3020, with the IRAM interferometer, at ∼1 resolution. This galaxy was selected from an IRAM-30 m survey of 30 galaxies at moderate redshift (z ∼ 0.2−0.6) to explore galaxy evolution and, in particular, the efficiency of star formation, in the redshift range filling the gap between local and very high-z objects. The CO emission is kinematically resolved, and about 50% of the total emission found in the 27 (97 kpc) single dish beam is not recovered by the interferometer. This indicates that some extended emission may be present on large scales (typically 7-15). The FIR-to-CO luminosity ratio follows the trend from local to high-z ultra-luminous starbursts.
The Astrophysical Journal Supplement Series, 2009
We have analyzed FUSE (905-1187Å) spectra of a sample of 16 local starburst galaxies. These galaxies cover almost three orders of magnitude in starformation rates and over two orders of magnitude in stellar mass. Absorption features from the stars and interstellar medium are observed in all the spectra. The strongest interstellar absorption features are generally blue-shifted by ∼ 50 to 300 km s −1 , implying the almost ubiquitous presence of starburst-driven galactic winds in this sample. The outflow velocites increase with both the star formation rate and the star formation rate per unit stellar mass, consistent with a galactic wind driven by the population of massive stars. We find outflowing coronal-phase gas (T ∼ 10 5.5 K) detected via the O VI absorption-line in nearly every galaxy. The O VI absorption-line profile is optically-thin, is generally weak near the galaxy systemic velocity, and has a higher mean outflow velocity than seen in the lower ionization lines. The relationship between the line width and column density for the O VI absorbing gas is in good agreement with expectations for radiatively cooling and outflowing gas. Such gas will be created in the interaction of the hot out-rushing wind seen in X-ray emission and cool dense ambient material. O VI emission is not generally detected in our sample, suggesting that radiative cooling by the coronal gas is not dynamically significant in draining energy from galactic winds. We find that the measured outflow velocities in the HI and HII phases of the interstellar gas in a given galaxy increase with the strength (equivalent width) of the absorption feature and not with the a FUV luminosity derived from FUSE LiF 2A continuum flux at 1150Å. Values are corrected for MW extinction using the method of and the E(B-V) values given in this table.
The Astrophysical Journal, 2009
We have imaged CO(J=7→6) and C I(3 P 2 → 3 P 1) emission in the host galaxy of the z=6.42 quasar SDSS J114816.64+525150.3 (hereafter: J1148+5251) through observations with the Plateau de Bure Interferometer. The region showing CO(J=7→6) emission is spatially resolved, and its size of 5 kpc is in good agreement with earlier CO(J=3→2) observations. In combination with a revised model of the collisional line excitation in this source, this indicates that the highly excited molecular gas traced by the CO J=7→6 line is subthermally excited (showing only 58±8% of the CO J=3→2 luminosity), but not more centrally concentrated. We also detect C I(3 P 2 → 3 P 1) emission in the host galaxy of J1148+5251, but the line is too faint to enable a reliable size measurement. From the C I(3 P 2 → 3 P 1) line flux, we derive a total atomic carbon mass of M CI =1.1×10 7 M ⊙ , which corresponds to ∼5×10 −4 times the total molecular gas mass. We also searched for H 2 O(J KaKc =2 12 →1 01) emission, and obtained a sensitive line luminosity limit of L ′ H2O <4.4×10 9 K km s −1 pc 2 , i.e., <15% of the CO(J=3→2) luminosity. The warm, highly excited molecular gas, atomic gas and dust in this quasar host at the end of cosmic reionization maintain an intense starburst that reaches surface densities as high as predicted by (dust opacity) Eddington limited star formation over kiloparsec scales.
Mapping the starburst in blue compact dwarf galaxies
Astronomy and Astrophysics, 2009
Aims. By means of optical Integral Field Spectroscopy observations, we aim to disentangle and characterize the starburst component in the Blue Compact Dwarf Galaxy Mrk 1418. In particular we propose to study the stellar and ionized gas morphology, to investigate the ionization mechanism(s) acting in the interstellar medium, to derive the physical parameters and abundances of the ionized gas. Methods. Integral Field Spectroscopy observations of Mrk 1418 were carried out with the Potsdam Multi-Aperture Spectrophotometer (PMAS) at the 3.5 m telescope at Calar Alto Observatory. The central 16 ′′ × 16 ′′ (1.14 × 1.14 kpc 2 at the distance of Mrk 1418) were mapped with a spatial sampling of 1 ′′ ; we took data in the 3590-6996 Å spectral range, with a linear dispersion of 3.2 Å per pixel. The seeing was about 1. ′′ 5. From these data we built maps of the most prominent emission lines, namely [O ii], Hβ, [O iii], Hα, [N ii] and [S ii] as well as of several continuum bands, plus maps of the main line ratios: [O iii]/Hβ, [N ii]/Hα, [S ii]/Hα, and Hα/Hβ, and derived the physical parameters and gaseous metal abundances of the different star-forming regions detected in the field of view.
A kiloparsec-scale hyper-starburst in a quasar host less than 1 gigayear after the Big Bang
Nature, 2009
The host galaxy of the quasar SDSS J114816.64+525150.3 (at redshift z=6.42, when the Universe was <1 billion years old) has an infrared luminosity of 2.2×10 13 L 1,2 ⊙ , presumably significantly powered by a massive burst of star formation 3,4,5,6 . In local examples of extremely luminous galaxies such as Arp 220, the burst of star formation is concentrated in the relatively small central region of < 100 pc radius 7,8 . It is unknown on which scales stars are forming in active galaxies in the early Universe, which are likely undergoing their initial burst of star formation. We do know that at some early point structures comparable to the spheroidal bulge of the Milky Way must have formed. Here we report a spatially resolved image of [CII] emission of the host galaxy of J114816.64+525150.3 that demonstrates that its star forming gas is distributed over a radius of ∼ 750 pc around the centre. The surface density of the star formation rate averaged over this region is ∼1000 M ⊙ year −1 kpc −2 . This surface density is comparable to the peak in Arp 220, though ∼2 orders of magnitudes larger in area. This vigorous star forming event will likely give rise to a massive spheroidal component in this system.
Lyα Emission in Starbursts: Implications for Galaxies at High Redshift
The Astrophysical Journal, 2003
We present the results of a high resolution UV 2-D spectroscopic survey of star forming galaxies observed with HST-STIS. Our main aim was to map the Lyα profiles to learn about the gas kinematics and its relation with the escape of Lyα photons and to detect extended Lyα emission due to scattering in gaseous halos. We have combined our data with previously obtained UV spectroscopy on other three star-forming galaxies. We find that the P-Cygni profile is spatially extended, smooth and spans several kiloparsecs covering a region much larger than the starburst itself. We propose a scenario whereby an expanding supershell is generated by the interaction of the combined stellar winds and supernova ejecta from the young starbursts, with an extended low density halo. The variety of observed Lyα profiles both in our sample and in high redshift starbursts is explained as phases in the time evolution of the super-shell expanding into the disk and halo of the host galaxy. The observed shapes, widths and velocities are in excellent agreement with the super-shell scenario predictions and represent a time sequence. We confirm that among the many intrinsic parameters of a star forming region that can affect the properties of the observed Lyα profiles, velocity and density distributions of neutral gas along the line of sight are by far the dominant ones, while the amount of dust will determine the intensity of the emission line, if any.