Papers by Jarle Brinchmann
Monthly Notices of …, Jan 1, 2003
The Astrophysical …, Jan 1, 2004
We utilize Sloan Digital Sky Survey imaging and spectroscopy of $53,000 star-forming galaxies at ... more We utilize Sloan Digital Sky Survey imaging and spectroscopy of $53,000 star-forming galaxies at z $ 0:1 to study the relation between stellar mass and gas-phase metallicity. We derive gas-phase oxygen abundances and stellar masses using new techniques that make use of the latest stellar evolutionary synthesis and photoionization models. We find a tight (AE0.1 dex) correlation between stellar mass and metallicity spanning over 3 orders of magnitude in stellar mass and a factor of 10 in metallicity. The relation is relatively steep from 10 8.5 to 10 10.5 M h À2 70 , in good accord with known trends between luminosity and metallicity, but flattens above 10 10.5 M . We use indirect estimates of the gas mass based on the H luminosity to compare our data to predictions from simple closed box chemical evolution models. We show that metal loss is strongly anticorrelated with baryonic mass, with lowmass dwarf galaxies being 5 times more metal depleted than L Ã galaxies at z $ 0:1. Evidence for metal depletion is not confined to dwarf galaxies but is found in galaxies with masses as high as 10 10 M . We interpret this as strong evidence of both the ubiquity of galactic winds and their effectiveness in removing metals from galaxy potential wells.
Monthly Notices of …, Jan 1, 2003
We develop a new method to constrain the star formation histories, dust attenuation and stellar m... more We develop a new method to constrain the star formation histories, dust attenuation and stellar masses of galaxies. It is based on two stellar absorption line indices, the 4000Å break strength and the Balmer absorption line index Hδ A . Together, these indices allow us to constrain the mean stellar ages of galaxies and the fractional stellar mass formed in bursts over the past few Gyr. A comparison with broad band photometry then yields estimates of dust attenuation and of stellar mass. We generate a large library of Monte Carlo realizations of different star formation histories, including starbursts of varying strength and a range of metallicities. We use this library to generate median likelihood estimates of burst mass fractions, dust attenuation strengths, stellar masses and stellar mass-to-light ratios for a sample of 122,808 galaxies drawn from the Sloan Digital Sky Survey. The typical 95% confidence range in our estimated stellar masses is ± 40 %. We study how the stellar mass-to-light ratios of galaxies vary as a function of absolute magnitude, concentration index and photometric pass-band and how dust attenuation varies as a function of absolute magnitude and 4000Å break strength. We also calculate how the total stellar mass of the present Universe is distributed over galaxies as a function of their mass, size, concentration, colour, burst mass fraction and surface mass density. We find that most of the stellar mass in the local Universe resides in galaxies that have, to within a factor of about 2, stellar masses ∼ 5×10 10 M ⊙ , half-light radii ∼ 3 kpc, and half-light surface mass densities ∼ 10 9 M ⊙ kpc −2 . The distribution of D n (4000) is strongly bimodal, showing a clear division between galaxies dominated by old stellar populations and galaxies with more recent star formation.
Urbana, Jan 1, 2008
This paper describes the Sixth Data Release of the Sloan Digital Sky Survey. With this data relea... more This paper describes the Sixth Data Release of the Sloan Digital Sky Survey. With this data release, the imaging of the northern Galactic cap is now complete. The survey contains images and parameters of roughly 287 million objects over 9583 deg 2 , including scans over a large range of Galactic latitudes and longitudes. The survey also includes 1.27 million spectra of stars, galaxies, quasars, and blank sky (for sky subtraction) selected over 7425 deg 2 . This release includes much more stellar spectroscopy than was available in previous data releases and also includes detailed estimates of stellar temperatures, gravities, and metallicities. The results of improved photometric calibration are now available, with uncertainties of roughly 1% in g, r, i, and z, and 2% in u, substantially better than the uncertainties in previous data releases. The spectra in this data release have improved wavelength and flux calibration, especially in the extreme blue and extreme red, leading to the qualitatively better determination of stellar types and radial velocities. The spectrophotometric fluxes are now tied to point-spread function magnitudes of stars rather than fiber magnitudes. This gives more robust results in the presence of seeing variations, but also implies a change in the spectrophotometric scale, which is now brighter by roughly 0.35 mag. Systematic errors in the velocity dispersions of galaxies have been fixed, and the results of two independent codes for determining spectral classifications and redshifts are made available. Additional spectral outputs are made available, including calibrated spectra from individual 15 minute exposures and the sky spectrum subtracted from each exposure. We also quantify a recently recognized Vol. 175 underestimation of the brightnesses of galaxies of large angular extent due to poor sky subtraction; the bias can exceed 0.2 mag for galaxies brighter than r ¼ 14 mag.
The Astrophysical …, Jan 1, 2009
This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the... more This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11,663 deg 2 of imaging data, with most of the ∼2000 deg 2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry on a 120 • long, 2. • 5 wide stripe along the celestial equator in the Southern Galactic Cap, with some regions covered by as many as 90 individual imaging runs. We include a co-addition of the best of these data, going roughly 2 mag fainter than the main survey over 250 deg 2 . The survey has completed spectroscopy over 9380 deg 2 ; the spectroscopy is now complete over a large contiguous area of the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog, reducing the rms statistical errors at the bright end to 45 milliarcseconds per coordinate. We further quantify a systematic error in bright galaxy photometry due to poor sky determination; this problem is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.
The Astrophysical …, Jan 1, 2006
This paper describes the Fourth Data Release of the Sloan Digital Sky Survey (SDSS), including al... more This paper describes the Fourth Data Release of the Sloan Digital Sky Survey (SDSS), including all survey-quality data taken through 2004 June. The data release includes five-band photometric data for 180 million objects selected over 6670 deg 2 and 673,280 spectra of galaxies, quasars, and stars selected from 4783 deg 2 of those imaging data using the standard SDSS target selection algorithms. These numbers represent a roughly 27% increment over those of the Third Data Release; all the data from previous data releases are included in the present release. The Fourth Data Release also includes an additional 131,840 spectra of objects selected using a variety of alternative algorithms, to address scientific issues ranging from the kinematics of stars in the Milky Way thick disk to populations of faint galaxies and quasars.
Monthly Notices of …, Jan 1, 2004
We present a comprehensive study of the physical properties of ∼ 10 5 galaxies with measurable st... more We present a comprehensive study of the physical properties of ∼ 10 5 galaxies with measurable star formation in the SDSS. By comparing physical information extracted from the emission lines with continuum properties, we build up a picture of the nature of star-forming galaxies at z < 0.2. We develop a method for aperture correction using resolved imaging and show that our method takes out essentially all aperture bias in the star formation rate (SFR) estimates, allowing an accurate estimate of the total SFRs in galaxies. We determine the SFR density to be 1.915 +0.02 −0.01 (rand.)
The Astrophysical …, Jan 1, 2007
This paper describes the Sixth Data Release of the Sloan Digital Sky Survey. With this data relea... more This paper describes the Sixth Data Release of the Sloan Digital Sky Survey. With this data release, the imaging of the Northern Galactic Cap is now complete. The survey contains images and parameters of roughly 287 million objects over 9583 deg 2 , including scans over a large range of Galactic latitudes and longitudes. The survey also includes 1.27 million spectra of stars, galaxies, quasars and blank sky (for sky subtraction) selected over 7425 deg 2 . This release includes much more extensive stellar spectroscopy than previously, and also includes detailed estimates of stellar temperatures, gravities, and metallicities. The results of improved photometric calibration are now available, with uncertainties of roughly 1% in g, r, i, and z, and 2% in u, substantially better than the uncertainties in previous data releases. The spectra in this data release have improved wavelength and flux calibration, especially in the extreme blue and extreme red, leading to the qualitatively better determination of stellar types and radial velocities. The spectrophotometric fluxes are now tied to point spread function magnitudes of stars rather than fiber magnitudes. This gives more robust results in the presence of seeing variations, but also implies a change in the spectrophotometric scale, which is now brighter by roughly 0.35 mags. Systematic errors in the velocity dispersions of galaxies have been fixed, and the results of two independent codes for determining spectral classifications and redshifts are made available. Additional spectral outputs are made available, including calibrated spectra from individual 15-minute exposures and the sky spectrum subtracted from each exposure. We also quantify a recently recognized under-estimation of the brightnesses of galaxies of large angular extent due to poor sky subtraction; the bias can exceed 0.2 mag for galaxies brighter than r = 14 mag.
Arxiv preprint astro-ph/ …, Jan 1, 2004
We use a complete sample of galaxies drawn from the Sloan Digital Sky Survey (SDSS) to study how ... more We use a complete sample of galaxies drawn from the Sloan Digital Sky Survey (SDSS) to study how structure, star formation and nuclear activity depend on local density and on stellar mass. Local density is estimated by counting galaxies above a fixed absolute magnitude limit within cylinders 2 Mpc in projected radius and ±500 km s −1 in depth. The stellar mass distribution of galaxies shifts by almost a factor of two towards higher masses between low and high density regions. At fixed stellar mass both star formation and nuclear activity depend strongly on local density, while structural parameters such as size and concentration are almost independent of it. Only for low mass galaxies (M * < 3 × 10 10 M ⊙ ) do we find a weak shift towards greater concentration and compactness in the highest density regions. The galaxy property most sensitive to environment is specific star formation rate. For galaxies with stellar masses in the range 10 10 − 3 × 10 10 M ⊙ , the median SFR/M * decreases by more than a factor of 10 as the population shifts from predominantly star-forming at low densities to predominantly inactive at high densities. This decrease is less marked, but still significant for high mass galaxies. Galaxy properties that are associated with star formation correlate strongly with local density. At fixed stellar mass twice as many galaxies host AGN with strong [OIII] emission in low density regions as in high. Massive galaxies in low-density environments also contain more dust. To gain insight into the processes that shut down star formation, we analyze correlations between spectroscopic indicators that probe the SFH on different timescales: the 4000Å break strength, the Balmerabsorption index Hδ A , and the specific star formation rate SFR/M * . The correlations between these indicators do not depend on environment, suggesting that the decrease in star formation activity in dense environments occurs over long (> 1 Gyr) timescales. Since structure does not depend on environment for galaxies with masses greater than 3 × 10 10 M ⊙ , the trends in recent star formation history (SFH), dust and nuclear activity in these systems cannot be driven by processes that alter structure, for example mergers or harrassment. The SFH-density correlation is strongest for small scale estimates of local density. We see no evidence that star formation history depends on environment more than 1 Mpc from a galaxy. Finally, we highlight a striking similarity between the changes in the galaxy population as a function of density and as a function of redshift. We use mock catalogues derived from N-body simulations to explain how this may be understood.
The Astrophysical …, Jan 1, 2004
We investigate the accretion-driven growth of supermassive black holes in the low-redshift univer... more We investigate the accretion-driven growth of supermassive black holes in the low-redshift universe using 23,000 narrow-emission-line (''type 2'') active galactic nuclei (AGNs) and the complete sample of 123,000 galaxies in the Sloan Digital Sky Survey from which they were drawn. We use the stellar velocity dispersions of the early-type galaxies and AGN hosts to estimate their black hole masses, and we use the AGN [O iii] k5007 emission line luminosities to estimate black hole accretion rates. We find that most present-day accretion occurs onto black holes with masses less than 10 8 M that reside in moderately massive galaxies (M Ã % 10 10 -10 11.5 M ) with high stellar surface mass densities ( Ã % 10 8:5 -10 9.5 M kpc À2 ) and young stellar populations. The volumeaveraged accretion rates of low-mass black holes (<3 ; 10 7 M ) imply that this population is growing on a timescale that is comparable to the age of the universe. Around half this growth takes place in AGNs that are radiating within a factor of 5 of the Eddington luminosity. Such systems are rare, making up only 0.2% of the lowmass black hole population at the present day. The rest of the growth occurs in lower luminosity AGNs. The growth timescale is more than 2 orders of magnitude longer for the population of the most massive black holes in our sample. The volume-averaged ratio of star formation to black hole accretion in bulge-dominated galaxies is $1000, in remarkable agreement with the observed ratio of stellar mass to black hole mass in nearby galaxy bulges. We conclude that (1) bulge formation and black hole formation are tightly coupled, even in present-day galaxies, and (2) the evolution of the AGN luminosity function documented in recent optical and X-ray surveys is driven by a decrease in the characteristic mass scale of actively accreting black holes.
The Astrophysical …, Jan 1, 1998
Several aspects of the evolution of star-forming galaxies are studied using measures of the 2dime... more Several aspects of the evolution of star-forming galaxies are studied using measures of the 2dimensional surface brightness profiles of a sample of 341 faint objects selected from the CFRS and LDSS redshift surveys that have been observed with the Hubble Space Telescope. The size function of disk scale lengths in disk-dominated galaxies (i.e. bulge to total ratios, B/T ≤ 0.5) is found to stay roughly constant to z ~ 1, at least for those larger disks with exponential scale lengths α -1 > 3.2 h 50 -1 kpc, where the sample is most complete and where the disk and bulge decompositions are most reliable. This result, which is strengthened by inclusion of the local de Jong et al (1996) size function, suggests that the scale lengths of typical disks can not have grown substantially with cosmic epoch since z ~ 1, unless a corresponding number of large disks
The Astrophysical …, Jan 1, 1998
Monthly Notices of …, Jan 1, 2000
Hubble Space Telescope images of a sample of 285 galaxies with measured redshifts from the CFRS a... more Hubble Space Telescope images of a sample of 285 galaxies with measured redshifts from the CFRS and Autofib-LDSS redshift surveys are analysed to derive the evolution of the merger fraction out to redshifts z ∼ 1. We have performed visual and machine-based merger identifications, as well as counts of bright pairs of galaxies with magnitude differences δm ≤ 1.5 mag. We find that the pair fraction increases with redshift, with up to ∼ 20% of the galaxies being in physical pairs at z ∼ 0.75 − 1. We derive a merger fraction varying with redshift as ∝ (1 + z) 3.2±0.6 , after correction for line-of-sight contamination, in excellent agreement with the merger fraction derived from the visual classification of mergers for which m = 3.4 ± 0.6. After correcting for seeing effects on the ground-based selection of survey galaxies, we conclude that the pair fraction evolves as ∝ (1 + z) 2.7±0.6 . This implies that an average L * galaxy will have undergone 0.8 to 1.8 merger events from z = 1 to z = 0, with 0.5 to 1.2 merger events occuring in a 2 Gyr time span at around z ∼ 0.9. This result is consistent with predictions from semi-analytical models of galaxy formation. From the simple co-addition of the observed luminosities of the galaxies in pairs, physical mergers are computed to lead to a brightening of 0.5 mag for each pair on average, and a boost in star formation rate of a factor of 2, as derived from the average [O II] equivalent widths. Mergers of galaxies are therefore contributing significantly to the evolution of both the luminosity function and luminosity density of the Universe out to z ∼ 1.
The Astrophysical Journal Letters, Jan 1, 2000
We discuss a new method for inferring the stellar mass of a distant galaxy of known redshift base... more We discuss a new method for inferring the stellar mass of a distant galaxy of known redshift based on the combination of a near-infrared luminosity and multi-band optical photometry. The typical uncertainty for field galaxies with I < 22 in the redshift range 0 < z < 1 is a factor 2. We apply this method to a newly-constructed sample of 321 field galaxies with redshifts and Hubble Space Telescope morphologies enabling us to construct the stellar mass density associated with various morphologies as a function of redshift. We find a marked decline with time in the stellar mass associated with peculiar galaxies accompanied by a modest rise in that observed for ellipticals. The result suggests that peculiars decline in abundance because they transform and merge into regular systems. The star formation rate per unit stellar mass indicates that massive systems completed the bulk of their star formation before redshift one, whereas dwarfs continue to undergo major episodes of activity until the present epoch.
The Astrophysical …, Jan 1, 2007
We measure star formation rates (SFRs) of ≈ 50, 000 optically-selected galaxies in the local univ... more We measure star formation rates (SFRs) 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 (ultraviolet) 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-measured emission lines (primarily Hα). Systematic deviations from perfect agreement between these two methods is shown to be due to differences in the dust attenuation estimates. In contrast to measurements based on Hα, UV provides reliable SFRs for galaxies with weak or no Hα emission, and where Hα is contaminated with an emission from an AGN (1/2 of the sample). We use full-SED SFRs to calibrate a simple prescription that uses GALEX far-UV magnitude and the UV slope to produce good dust-corrected SFRs for normal star-forming galaxies. The specific SFR (SFR normalized by stellar mass) 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 Hα emission (the latter two groups forming the bulk of the optical red sequence). 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. On the other hand, 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 Hα emission show signs of star formation in the UV. We derive a UV-based cosmic star formation density at z = 0.1 with significantly smaller total error than previous measurements.
The Astrophysical …, Jan 1, 2004
The distribution in color and absolute magnitude is presented for 55,158 galaxies taken from the ... more The distribution in color and absolute magnitude is presented for 55,158 galaxies taken from the Sloan Digital Sky Survey in the redshift range 0.08 < z < 0.12, as a function of galaxy number overdensity in a line-of-sight cylinder of transverse radius 1 h −1 Mpc. In all environments, bulge-dominated galaxies (defined to be those with radial profiles best fit with large Sérsic indices) form a narrow, well defined colormagnitude relation. Although the most luminous galaxies reside preferentially in the highest density regions, there is only a barely detectable variation in the color (zeropoint) or slope of the color-magnitude relation (< 0.02 mag in 0.
The Astrophysical …, Jan 1, 1999
Two-dimensional surface photometry has been performed on a magnitude-limited sample of 46 field g... more Two-dimensional surface photometry has been performed on a magnitude-limited sample of 46 field galaxies that are classified as ellipticals based on two-dimensional fitting of their luminosity profiles using Hubble Space Telescope imaging. These galaxies are described well by a deVaucouleurs R 1/4 profile. The sample was selected from the combined Canada-France and LDSS redshift surveys and spans the redshift range 0.20< z <1.00. This analysis reveals several clear evolutionary trends. First, the relationship between galaxy half-light radius and luminosity evolves with redshift such that a galaxy of a given size is more luminous by ∆M B = −0.97 ± 0.14 mag at z = 0.92 relative to the local cluster elliptical relation. Second, the mean rest-frame color shifts blueward with redshift by ∆(U − V ) = −0.68 ± 0.11 at z = 0.92 relative to the same relation in the Coma cluster. These shifts in color and luminosity of field elliptical galaxies are similar to those measured for cluster ellipticals. Approximately 1/3 of these elliptical galaxies (independent of redshift) exhibit [OII] 3727 emission lines with equivalent widths > 15 angstroms indicating ongoing star formation. Therefore, field elliptical galaxies are not composed entirely of very old stellar populations. Estimated star-formation rates together with stellar population evolutionary models imply that ≤ 5% of the stellar mass in the elliptical galaxy population has been formed since z = 1. We find some evidence that the dispersion in color among field ellipticals at z ∼ 0.55 may be larger than that seen among samples of cluster ellipticals and S0 galaxies at similar redshift. We see no evidence for a decline in the space density of early-type galaxies with look-back time. The < V /V max > statistics and a comparison with local luminosity functions are both consistent with the view that the population of massive early-type galaxies was largely 1 Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy Inc., under NASA contract NAS 5-26555. 2 Based in part on data obtained through the facilities of the Canadian Astronomy Data Centre. 1 in place by z ∼ 1. This implies that merging is not required since that time to produce the present-day space density of elliptical galaxies. However, the statistics are poor: a larger sample is required to produce a decisive result.
Monthly Notices of …, Jan 1, 2005
We derive stellar metallicities, light-weighted ages and stellar masses for a magnitudelimited sa... more We derive stellar metallicities, light-weighted ages and stellar masses for a magnitudelimited sample of 175,128 galaxies drawn from the Sloan Digital Sky Survey Data Release Two (SDSS DR2). We compute median-likelihood estimates of these parameters using a large library of model spectra at medium-high resolution, covering a comprehensive range of star formation histories. The constraints we derive are set by the simultaneous fit of five spectral absorption features, which are well reproduced by our population synthesis models. By design, these constraints depend only weakly on the α/Fe element abundance ratio. Our sample includes galaxies of all types spanning the full range in star formation activity, from dormant early-type to actively starforming galaxies. By analysing a subsample of 44,254 high-quality spectra, we show that, in the mean, galaxies follow a sequence of increasing stellar metallicity, age and stellar mass at increasing 4000Å-break strength. For galaxies of intermediate mass, stronger Balmer absorption at fixed 4000Å-break strength is associated with higher metallicity and younger age. We investigate how stellar metallicity and age depend on total galaxy stellar mass. Low-mass galaxies are typically young and metal-poor, massive galaxies old and metal-rich, with a rapid transition between these regimes over the stellar mass range 3 × 10 9 M * 3 × 10 10 M ⊙ . Both high-and low-concentration galaxies follow these relations, but there is a large dispersion in stellar metallicity at fixed stellar mass, especially for low-concentration galaxies of intermediate mass.
The Astronomical …, Jan 1, 2009
The Sloan Extension for Galactic Understanding and Exploration (SEGUE) Survey obtained ≈240,000 m... more The Sloan Extension for Galactic Understanding and Exploration (SEGUE) Survey obtained ≈240,000 moderateresolution (R ∼ 1800) spectra from 3900 Å to 9000 Å of fainter Milky Way stars (14.0 < g < 20.3) of a wide variety of spectral types, both main-sequence and evolved objects, with the goal of studying the kinematics and populations of our Galaxy and its halo. The spectra are clustered in 212 regions spaced over three quarters of the sky. Radial velocity accuracies for stars are σ (RV) ∼ 4 km s −1 at g < 18, degrading to σ (RV) ∼ 15 km s −1 at g ∼ 20. For stars with signal-to-noise ratio >10 per resolution element, stellar atmospheric parameters are 4377
Monthly Notices of the …, Jan 1, 2006
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Papers by Jarle Brinchmann