Measure Of Star Formation Rate Research Articles

UV Star Formation Rates in the Local Universe

We measure star formation rates of ~50,000 optically-selected galaxies in the local universe (z~0.1), spanning a range from gas-rich dwarfs to massive ellipticals. We obtain dust-corrected SFRs by fitting the GALEX (UV) and SDSS (optical) photometry to a library of population synthesis models that include dust attenuation. For star-forming galaxies, our UV-based SFRs compare remarkably well with those derived from SDSS H alpha. Deviations from perfect agreement between these two methods are due to differences in the dust attenuation estimates. In contrast to H alpha, UV provides reliable SFRs for galaxies with weak or no H alpha emission, and where H alpha is contaminated with an emission from an AGN. We use full-SED SFRs to calibrate a simple prescription that uses GALEX UV magnitudes to produce good SFRs for normal star-forming galaxies. The specific SFR is considered as a function of stellar mass for (1) star-forming galaxies with no AGN, (2) those hosting an AGN, and for (3) galaxies without H alpha emission. We find that the three have distinct star formation histories, with AGN lying intermediate between the star-forming and the quiescent galaxies. Normal star forming galaxies (without an AGN) lie on a relatively narrow linear sequence. Remarkably, galaxies hosting a strong AGN appear to represent the massive continuation of this sequence. Weak AGN, while also massive, have lower SFR, sometimes extending to the realm of quiescent galaxies. We propose an evolutionary sequence for massive galaxies that smoothly connects normal star-forming galaxies to quiescent (red sequence) galaxies via strong and weak AGN. We confirm that some galaxies with no H alpha emission show signs of SF in the UV. We derive a UV-based cosmic SFR density at z=0.1 with smaller total error than previous measurements (abridged).

The star formation rate of Ca II and damped Lyman absorbers at 0.4 < z < 1.3

Using stacked Sloan Digital Sky Survey (SDSS) spectra, we present the detection of (O II) λλ3727, 3730 nebular emission from the galaxies hosting Ca II absorption line systems and galaxies hosting Mg II-selected damped Lyman α (DLA) absorbers. Both samples of ab- sorbers, 345 Ca II systems and 3461 Mg II-selected DLA systems, span the redshift interval 0.4 zabs < 1.3; all of the former and half the latter sample are expected to be bona fide DLAs. The measured star formation rate (SFR) per absorber from light falling within the SDSS fi- bre apertures (corresponding to physical radii of 6-9 h −1 kpc) is 0.11-0.14 Myr −1 for the Mg II-selected DLAs and 0.11-0.48 Myr −1 for the Ca II-absorbers. These results represent the first estimates of the average SFR in an absorption-selected galaxy population from the di- rect detection of nebular emission. Adopting the currently favoured model in which DLAs are large, with radii 9 h −1 kpc, and assuming no attenuation of the (O II) emission by dust, leads us to conclude that the SFR per unit area of Mg II-selected DLAs falls an order of magnitude below the predictions of the Schmidt law, which relates the SFR to the H I column density at z ∼ 0. While DLA sightlines are known to contain little dust, the unknown geometry of the dust distribution in the galaxies causes the main uncertainty in our results. The contribution of both DLA and Ca II absorbers to the total observed star formation rate density, ˙ ρ ∗ , in the redshift range 0.4 < z < 1.3, is small, 10 and 3 per cent, respectively. The result contrasts with the conclusions of Hopkins et al. that DLA absorbers can account for the majority of the total observed ˙ ρ ∗ in the same redshift range. The disagreement is a direct consequence of the much lower SFR per unit area we observe than predicted by the Schmidt law. Our results effectively rule out a picture in which DLA absorbers are the sites in which a large fraction of the total ˙ ρ ∗ at redshifts z 1 occurs.

The Local Rate and the Progenitor Lifetimes of Short‐Hard Gamma‐Ray Bursts: Synthesis and Predictions for the Laser Interferometer Gravitational‐Wave Observatory

The recent discovery of the first four afterglows of short-hard gamma-ray bursts (SHBs) suggests that they typically result from long-lived progenitor systems. The most popular progenitor model invokes the merger of either double neutron star (DNS) binaries or neutron star-black hole (NS-BH) systems. Such events are strong sources of gravitational waves (GWs) and might be detected by ground-based GW observatories. In this work we combine the census of SHB observations with refined theoretical analysis to perform a critical evaluation of the compact binary model. We then explore the implications for GW detection of these events. Beginning from the measured star formation rate through cosmic time, we consider what intrinsic luminosity and lifetime distributions can reproduce the known SHB redshifts and luminosities as well as the peak flux distribution of the large BATSE SHB sample. We find the following: (1) The typical progenitor lifetime is long. Assuming lognormal lifetime distribution, the typical lifetime is >4 (1) Gyr (2 σ [3 σ] c.l.). If the lifetime distribution is a power law with index η, then η > -0.5 (-1) (2 σ [3 σ] c.l.). This result is difficult to reconcile with the properties of the observed Galactic DNS population, suggesting that if SHBs do result from DNS mergers, then the observed Galactic binaries do not represent the cosmic one. (2) We find that the local rate of SHBs is larger than 10 Gpc-3 yr-1 and may be higher by several orders of magnitude, significantly above previous estimates. (3) Assuming that SHBs do result from compact binaries, our predictions for the LIGO and VIRGO event rates are encouraging: the chance for detection by current facilities is not negligible, while a coincident detection of GW and electromagnetic radiation from an SHB is guaranteed for next-generation observatories.

Star Formation Rates of a z~1 DEEP2 Galaxy Sample from LIRIS Multi-slit Hα Spectroscopy

AbstractWe present preliminary results of Hα near-infrared (NIR) spectroscopy of 16 galaxies with redshifts in the range 0.8 ≤ z ≤ 1.0 drawn from the DEEP2 Galaxy Redshift Survey. The spectra were taken using the multi-slit mode of LIRIS (Long-slit Intermediate Resolution Infrared Spectrograph), installed at the 4.2-m WHT. Twelve out of 16 spectra yield robust (&gt;5σ) Hα detections. We compare star formation rates (SFRs) from Hα luminosities to those derived from DEEP2 rest-frame UV measurements. This study is part of a larger program to obtain accurate Hα luminosities of about 50 star-forming galaxies at z ~ 1 in the Extended Groth Strip. Our scientific goals are the measurement of SFRs from Hα, and the comparison and calibration of Hα and other SFR tracers at z ~ 1. The study will be complemented with galaxy stellar masses, reddening estimates, galaxy morphologies and metallicities.

New test of supernova electron neutrino emission using Sudbury Neutrino Observatory sensitivity to the diffuse supernova neutrino background

Supernovae are rare nearby, but they are not rare in the Universe, and all past core-collapse supernovae contributed to the Diffuse Supernova Neutrino Background (DSNB), for which the near-term detection prospects are very good. The Super-Kamiokande limit on the DSNB electron {\it antineutrino} flux, $\phi(E_\nu > 19.3 {\rm MeV}) < 1.2$ cm$^{-2}$ s$^{-1}$, is just above the range of recent theoretical predictions based on the measured star formation rate history. We show that the Sudbury Neutrino Observatory should be able to test the corresponding DSNB electron {\it neutrino} flux with a sensitivity as low as $\phi(22.5 < E_\nu < 32.5 {\rm MeV}) \simeq 6 $ cm$^{-2}$ s$^{-1}$, improving the existing Mont Blanc limit by about three orders of magnitude. While conventional supernova models predict comparable electron neutrino and antineutrino fluxes, it is often considered that the first (and forward-directed) SN 1987A event in the Kamiokande-II detector should be attributed to electron-neutrino scattering with an electron, which would require a substantially enhanced electron neutrino flux. We show that with the required enhancements in either the burst or thermal phase $\nu_e$ fluxes, the DSNB electron neutrino flux would generally be detectable in the Sudbury Neutrino Observatory. A direct experimental test could then resolve one of the enduring mysteries of SN 1987A: whether the first Kamiokande-II event reveals a serious misunderstanding of supernova physics, or was simply an unlikely statistical fluctuation. Thus the electron neutrino sensitivity of the Sudbury Neutrino Observatory is an important complement to the electron antineutrino sensitivity of Super-Kamiokande in the quest to understand the DSNB.

TheHubble Space TelescopeACS Grism Parallel Survey. II. First Results and a Catalog of Faint Emission-Line Galaxies atz ≤ 1.6

We present the first results from the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Grism Parallel Survey, a large program obtaining deep, slitless ACS grism spectroscopy of high-latitude HST parallel fields. We report on 11 high Galactic latitude fields here, each with grism integration times of more than 12 ks. We identify 601 compact emission-line galaxies at z ≤ 1.6, reaching emission lines to a flux limit of ≳5 × 10-18 ergs cm-2 s-1 (3 σ). We determine redshifts by cross-correlation of the target spectra with template spectra, followed by visual inspection. We measure star formation rates from the observed [O II] λ3727, [O III] λ5007, and Hα line fluxes. Follow-up observations with the Keck telescope of one of the survey fields confirms our classification and redshifts with σ(z) ≃ 0.02. This is one of the deepest emission-line surveys to date, covering a total area of 121 arcmin2. The rough estimate of the comoving number density of emission-line galaxies in our survey at 0.3 < z < 1.3 is ∼4.5 × 10-3 h Mpc-3. We reach deeper into the emission-line luminosity function than either the STIS or NICMOS grism parallel surveys, finding an apparent space density of emission-line galaxies several times higher than those surveys. Because of the ACS high spatial resolution, our survey is very sensitive to faint, compact galaxies with strong emission lines and weak continua. The ACS grism survey provides the comoving star formation density at z ≤ 1.6 at a high level of completeness.

H i Observations of SA 68-6597: The Faintest Blue Compact Dwarf Galaxy

Blue compact dwarf galaxies (BCDs) are faint (MB ≤ -17 mag), compact (R < 1 kpc), and at least qualitatively very blue galaxies, due to active star formation, and have low metallicities. Found serendipitously as part of a redshift survey of faint galaxies with the Keck Telescope (DEEP), SA 68-6597 is at a distance of 80 Mpc, and is one of the faintest (-12.4 mag), lowest metallicity (~0.05 Z☉) BCDs known. Its Hβ line width of σ = 27 km s-1 and small size, Reff ~ 190 pc, suggest that it is an extremely low mass galaxy. We have used the Arecibo telescope to measure the H I properties of SA 68-6597 in order to better constrain its total mass and its potential for future star formation. SA 68-6597 has a M = (1.4 ± 0.4) × 107 M☉ and an H I FWHM line width of 33. Combining the H I line width with an estimate of the size of the H I disk, we derive a Mdyn 3 × 107 M☉. The values M/LB = 1.0 ± 0.3 M☉/L☉, Mdyn/LB ≥ 2 M☉/L☉, and M/Mdyn 0.47 are typical for BCDs. Combining the measured star formation rate of 0.003 M☉ yr-1 with the H I mass, we derive a gas depletion timescale of 5 ± 2 Gyr. While SA 68-6597 is a fainter, lower mass, higher metallicity counterpart to other BCDs like I Zw 18 and SBS 0335-052, its H I properties suggest that it will not evolve dramatically in the near future. Given the limits on its gaseous and dynamical masses, SA 68-6597 may be able to evolve into a moderately massive dwarf spheroidal galaxy.

Star formation rates of distant luminous infrared galaxies derived from Hα and IR luminosities

We present a study of the star formation rate (SFR ) for a sample of 16 distant galaxies detected by ISOCAM at 15 μ m in the CFRS0300+00 and CFRS1400+52 fields. Their high quality and intermediate resolution VLT/FORS spectra have allowed a proper correction of the Balmer emission lines from the underlying absorption. Extinction estimates using the Hβ /Hγ and the Hα /Hβ Balmer decrement are in excellent agreement, providing a robust measurement of the instantaneous SFR based on the extinction-corrected Hα luminosity. Star formation has also been estimated exploiting the correlations between IR luminosity and those at MIR and radio wavelengths. Our study shows that the relationship between the two SFR estimates follow two distinct regimes: (1) for galaxies with SFR IR below ~100 /yr, the SFR deduced from Hα measurements is a good approximation of the global SFR and (2) for galaxies near ULIRG regime. The corrected Hα SFR understimated the SFR by a factor of 1.5 to 2. Our analyses suggest that heavily extincted regions completely hidden in optical bands (such as those found in Arp 220) contribute less than 20% of the global budget of star formation up to .

Massive galaxy clusters as gravitational telescopes for distant supernovae

We investigate the potential of using massive clusters as gravitational telescopes for searches and studies of supernovae of Type Ia and Type II in optical and near-infrared bands at central wavelengths in the interval 0.8–1.25 μm. Using high-redshift supernova rates derived from the measured star formation rate, we find the most interesting effects for the detection of core-collapse SNe in searches at limiting magnitudes mag, where the total detection rate could be significantly enhanced and the number of detectable events is considerable even in a small field. For shallower searches, ~24 mag, a net gain factor of up to 3 in the discovery rate could be obtained, and yet a much larger factor for very high source redshifts. For programs such as the GOODS/ACS transient survey, the discovery rate of supernovae beyond could be significantly increased if the observations were done in the direction of massive clusters. For extremely deep observations, mag, or for very bright SNe (e.g. Type Ia) the competing effect of field reduction by lensing dominates, and fewer supernovae are likely to be discovered behind foreground clusters.

Star Formation Rates in Interacting Starburst Galaxies

By narrowband imaging in Hα and in the adjacent red stellar continuum we have studied the rate and distribution of star formation in 43 systems of luminous and ultraluminous IR galaxies currently undergoing interaction and merging. These galaxies are amongst the most luminous at 60 μm and range in distance from ~50 up to 100 Mpc. Here we present the Hα and the adjacent red-continuum narrowband images, and we compare the star formation rates derived from Hα with those estimated from the IR luminosity. We find clear evidence for substantial extinction and obscuration of star-forming regions in the optical. Without correction for reddening in the host galaxy or correction for [N II] contamination, the star formation rates derived for Hα are typically 0.5-1.0 dex lower than those estimated from the IR flux, and the scatter in the correlation is very large. However, an unexpected result is that when spectroscopic data are used to eliminate objects dominated by an active nucleus, to determine the galaxian extinction, and to correct the Hα flux for both reddening and for the contamination by the [N II] emission, a remarkably good correlation emerges between the star formation rates estimated from the Hα flux and those derived from the FIR continuum. In addition, a strong correlation is found between the extinction in the line-emitting region, AHα, and the rate of star formation. Our results invalidate the use of Hα imaging as a reliable indicator of star formation in starburst galaxies unless spectroscopic data are also available. This has important implications for the determination of star formation rates in high-redshift galaxies. Finally, we find no correlation between the measured star formation rates, and the interaction class, suggesting that the enhanced star formation rates triggered by the interaction continue throughout the whole of the merging sequence.

Star Formation History in the NICMOS Northern Hubble Deep Field

We present the results of an extensive analysis of the star formation rates determined from the NICMOS deep images of the northern Hubble Deep Field. We use SED template fitting photometric techniques to determine both the redshift and the extinction for each galaxy in our field. Measurement of the individual extinctions provides a correction for star formation hidden by dust obscuration. We determine star formation rates for each galaxy based on the 1500 A UV flux and add the rates in redshift bins of width 1.0 centered on integer redshift values. We find a rise in the star formation rate from a redshift of 1 to 2 then a falloff from a redshift of 2 to 3. However, within the formal limits of the error bars this could also be interpreted as a constant star formation rate from a redshift of 1 to 3. The star formation rate from a redshift of 3 to 5 is roughly constant followed by a possible drop in the rate at a redshift of 6. The measured star formation rate at a redshift of 6 is approximately equal to the present day star formation rate determined in other work. The high star formation rate measured at a redshift of 2 is due to the presence of two possible ULIRGs in the field. If real, this represents a much higher density of ULIRGs than measured locally. We also develop a new method to correct for faint galaxies or faint parts of galaxies missed by our sensitivity limit, based on the assumption that the star formation intensity distribution function is independent of redshift. We measure the 1.6 μm surface brightness due to discrete sources and predict the 850 μm brightness of all of our galaxies based on the determined extinction. We find that the far-infrared fluxes predicted in this manner are consistent with the lack of detections of 850 μm sources in the deep NICMOS HDF, the measured 850 μm sky brightness due to discrete sources and the ratio of optical-UV sky brightness to far-infrared sky brightness. From this we infer that we are observing a population of sources that contributes significantly to the total star formation rate and these sources are not overwhelmed by the contribution from sources such as the extremely superluminous galaxies represented by the SCUBA detections. We have estimated the errors in the star formation rate due to a variety of sources including photometric errors, the near-degeneracy between reddening and intrinsic spectral energy distribution as well as the effects of sampling errors and large-scale structure. We have tried throughout to give as realistic and conservative an estimate of the errors in our analysis as possible.

The Extreme Outer Regions of Disk Galaxies: Star Formation and Metal Abundances

AbstractThe extreme outer regions of disk galaxies, lying at or beyond the classical optical radius defined by R25, present an opportunity to study star formation and chemical evolution under unique physical conditions, possibly reminscent of those which existed during the early stages of disk evolution. We present here some of the first results from a large study to measure star formation rates and metallicities in the extreme outer limits of a sample of nearby spiral galaxies. Despite their low gas column densities, massive star formation is often observed in these outer parts, but at an azimuthally–averaged rate much lower than that seen in the inner disk. Gas-phase O/H abundances of roughly 10% solar characterize the gas at 1.5–2 R25. The implications of our results for star formation ‘laws’ and models of disk evolution are discussed.

Star Formation Rates in Faint Radio Galaxies

The decimetric radio continuum luminosity of a star-forming galaxy appears to be directly proportional to the rate of formation of supernovae in the galaxy. Since decimetric radiation does not suffer significant extinction and is not directive, radio luminosities may thus provide a particularly straightforward way to determine the current rate of star formation. Using a sample of over 700 local galaxies we confirm the utility of the radio luminosity as a measure of star formation rate by showing concordance with the rates predicted by U-band, H-alpha, and far-infrared luminosites. We also show that there are systematic discrepancies between these various indicators, suggesting that the H-alpha luminosity may underestimate the star formation rate by approximately an order of magnitude when the star formation rate is more than 20 solar mass per year. We use this calibration and the measured radio luminosities of sub-mJy radio sources to infer the star formation rate in approximately 60 star-forming galaxies at moderate (z = 0.1) redshifts, both as the actual rate and as the fraction of the existing mass of stars in the galaxy. For some of these objects the inferred current rate of star formation could increase the stellar mass in the galaxy by approximately 10% over an interval of about 30 Myr.