Diffuse Far-Uv Line Emission from the Low-Redshift Lyman Break Galaxy Analog KISSR242 (original) (raw)
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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 Astronomical Journal, 2011
We present 46 rest-frame ultraviolet (UV) spectra of 28 local starburst and star-forming galaxies which were observed with the Faint Object Spectrograph (FOS) and the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) at a spectral resolution of a few 100 km s 1. We compare the HST spectra with lower resolution International Ultraviolet Explorer (IUE) spectra of the same galaxies and find systematic differences: the bright star clusters targeted in HST's ~1 apertures provide about 15% of the starburst luminosity traced by IUE's 10 20 aperture; they are bluer and have stronger stellar-wind features suggesting that the HST apertures have preferentially been placed on the youngest areas of the burst. In contrast, lines arising from the interstellar medium (ISM) show similar equivalent widths in both the large and small aperture observations, suggesting similar ISM properties from larger to smaller scales. In order to quantify the UV spectral morphology of star-forming galaxies, we created a set of UV line indices similar to the standard optical Lick indices. We discuss the relation between the UV spectral morphology and the properties of the galaxy host. We present our atlas of FOS and GHRS spectra both in print and electronically. The data set is useful as a baseline for comparisons with observations of the rest-frame UV spectra of star-forming galaxies at high redshift.
The Astrophysical Journal, 2021
Detailed analyses of high-redshift galaxies are challenging due to their faintness, but this difficulty can be overcome with gravitational lensing, in which the magnification of the flux enables high signal-to-noise ratio (S/N) spectroscopy. We present the rest-frame ultraviolet (UV) Keck Echellette Spectrograph and Imager (ESI) spectrum of the newly discovered = 2.79 lensed galaxy SDSS J1059+4251. With an observed magnitude F814W = 18.8 and a magnification factor = 31 ± 3, J1059+4251 is both highly magnified and intrinsically luminous, about two magnitudes brighter than * UV at ∼ 2-3. With stellar mass * = (3.22 ± 0.20) × 10 10 M , star formation rate SFR = 50 ± 7 M yr −1 , and stellar metallicity * 0.15 − 0.5 , J1059+4251 is typical of bright star-forming galaxies at similar redshifts. Thanks to the high S/N and the spectral resolution of the ESI spectrum, we are able to separate the interstellar and stellar features and derive properties that would be inaccessible without the aid of the lensing. We find evidence of a gas outflow with speeds up to −1000 km s −1 , and of an inflow that is probably due to accreting material seen along a favorable line of sight. We measure relative elemental abundances from the interstellar absorption lines and find that-capture elements are overabundant compared to iron-peak elements, suggestive of rapid star formation. However, this trend may also be affected by dust depletion. Thanks to the high data quality, our results represent a reliable step forward in the characterization of typical galaxies at early cosmic epochs.
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, 2008
used the Galaxy Evolution Explorer (GALEX) UV imaging survey to show that there exists a rare population of nearby compact UV-luminous galaxies (UVLGs) that closely resembles high redshift Lyman break galaxies (LBGs). We present HST images in the UV, optical, and Hα, and resimulate them at the depth and resolution of the GOODS/UDF fields to show that the morphologies of UVLGs are also similar to those of LBGs. Our sample of 8 LBG analogs thus provides detailed insight into the connection between star formation and LBG morphology. Faint tidal features or companions can be seen in all of the rest-frame optical images, suggesting that the starbursts are the result of a merger or interaction. The UV/optical light is dominated by unresolved (∼100-300 pc) super starburst regions (SSBs). A detailed comparison with the galaxies Haro 11 and VV 114 at z = 0.02 indicates that the SSBs themselves consist of diffuse stars and (super) star clusters. The structural features revealed by the new HST images occur on very small physical scales and are thus not detectable in images of high redshift LBGs, except in a few cases where they are magnified by gravitational lensing. We propose, therefore, that LBGs are mergers of gas-rich, relatively low-mass (M * ∼ 10 10 M ⊙ ) systems, and that the mergers trigger the formation of SSBs. If galaxies at high redshifts are dominated by SSBs, then the faint end slope of the luminosity function is predicted to have slope α ∼ 2. Our results are the most direct confirmation to date of models that predict that the main mode of star formation in the early universe was highly collisional.
AstroSat detection of Lyman continuum emission from a z = 1.42 galaxy
Nature Astronomy, 2020
One of the outstanding problems of current observational cosmology is to understand the nature of sources that produced the bulk of the ionizing radiation after the Cosmic Dark Age. Direct detection of these reionization sources 1 is practically infeasible at high redshift due to the steep decline of intergalactic medium transmission 2,4. However, a number of low-redshift analogs emitting Lyman continuum at 900Å restframe are now detected at z < 0.4 [5, 6, 7, 8, 9] and there are detections in the range 2.5 < z < 3.5 [10, 11, 12, 13, 14, 15] also. Here, we report the detection of Lyman continuum emission with a high escape fraction (¿20%) from a low-mass clumpy galaxy at z=1.42, in the middle of the redshift range where no detection has been made before and near the peak of the Cosmic Star-formation history 16. The observation was made in the Hubble Extreme Deep field 17 by the wide-field UltraViolet Imaging Telescope 18 on-board AstroSat 19. This is the first detection of Extreme Ultraviolet radiation from a distant galaxy at a rest-frame wavelength of 600, and it opens up a new window to constrain the shape of the ionization spectrum. Further observations with AstroSat should significantly increase the sample of Lyman continuum leaking galaxies at Cosmic Noon.
Ultraviolet Light from Young Stars in GEMS Quasar Host Galaxies at 1.8 z 2.75
The Astrophysical Journal, 2004
We have performed HST imaging of a sample of 23 high-redshift (1.8 < z < 2.75) Active Galactic Nuclei, drawn from the combo-17 survey. The sample contains moderately luminous quasars (M B ∼ −23). The data are part of the gems imaging survey that provides high resolution optical images obtained with the Advanced Camera for Surveys in two bands (F606W and F850LP), sampling the rest-frame UV flux of the targets. To deblend the AGN images into nuclear and resolved (host galaxy) components we use a PSF subtraction technique that is strictly conservative with respect to the flux of the host galaxy. We resolve the host galaxies in both filter bands in 9 of the 23 AGN, whereas the remaining 14 objects are considered non-detections, with upper limits of less than 5 % of the nuclear flux. However, when we coadd the unresolved AGN images into a single high signal-to-noise composite image we find again an unambiguously resolved host galaxy. The recovered host galaxies have apparent magnitudes of 23.0 < F606W < 26.0 and 22.5 < F850LP < 24.5 with rest-frame UV colours in the range −0.2 < (F606W − F850LP) obs < 2.3. The rest-frame absolute magnitudes at 200 nm are −20.0 < M 200 nm < −22.2. The photometric properties of the composite host are consistent with the individual resolved host galaxies. We find that the UV colors of all host galaxies are substantially bluer than expected from an old population of stars with formation redshift z ≤ 5, independent of the assumed metallicities. These UV colours and luminosities range up to the values found for Lyman-break galaxies (LBGs) at z = 3. Our results suggest either a recent starburst, of e.g. a few per cent of the total stellar mass and 100 Myrs before observation, with mass-fraction and age strongly degenerate, or the possibility that the detected UV emission may be due to young stars forming continuously. For the latter case we estimate star formation rates of typically ∼6 M ⊙ yr −1 (uncorrected for internal dust attenuation), which again lies in the range of rates implied from the UV flux of LBGs. Our results agree with the recent discovery of enhanced blue stellar light in AGN hosts at lower redshifts.
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 [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.