Optical photometry of the UCM lists I and II

Pérez‐González, Pablo G.; Gallego, J.; Zamorano, J.; Paz, A. Gil de

doi:10.1051/0004-6361:20000153

Cited by 14 publications

(14 citation statements)

References 37 publications

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“…The specific frequency measurements indicate that RSGs brighter than M K = −10 account for 1.5% of the K−band light. If M81 is assumed to be a typical Sb galaxy, with 16% of its light coming from the bulge (Perez-Gonzalez et al 2001), then there should be ∼ 3300 RSGs with M K < −10 in the disk of M81. Table 4 of Bell & Kennicutt (2001), and the calibrations given in their Equations 2 and 3, the present-day SFR of M81 is 0.24 M ⊙ year −1 based on the UV flux, and 0.36 M ⊙ year −1 based on the Hα flux.…”

Section: Estimating the Sfr In M81 25 Myr In The Pastmentioning

confidence: 99%

Red Supergiants in the Disk of M81: Tracing the Spatial Distribution of Star Formation 25 Myr in the Past1

Davidge

2006

PUBL ASTRON SOC PAC

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Near-infrared images, obtained with the CFHTIR imager on the Canada-France-Hawaii Telescope, are used to investigate the brightest red stars in the disk of the nearby spiral galaxy M81. Red supergiants (RSGs) form a well-defined sequence on the color-magnitude diagrams (CMDs) that peaks near M K = −11.5; RSGs with this peak brightness are seen throughout all fields that were studied, indicating that star formation occured over a large part of the M81 disk only ∼ 10 Myr in the past. The number of RSGs per unit integrated K−band light is compared at various locations in the disk. The number density of bright RSGs is similar in three of four fields, indicating that the bright RSGs tend to be well mixed with the older stellar populations that dominate the integrated light in the K−band. However, the density of bright RSGs in a northern disk field is ∼ 2× higher than average, suggesting that the SFR in this part of the disk was higher than average 10 − 25 Myr in the past. The northern disk field contains areas of on-going star formation, and it is suggested that it is a region of prolonged star-forming activity. The number density of RSGs that formed during the past 10−25 Myr at galactocentric distances between ∼ 4 and 7 kpc is also comparable with that which formed between ∼ 7 and 10 kpc. We conclude that star-forming activity in M81 during the past 10 − 25 Myr (1) was distributed over a larger fraction of the disk than it is at the present day, and (2) was not restricted to a

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Section: Estimating the Sfr In M81 25 Myr In The Pastmentioning

confidence: 99%

Red Supergiants in the Disk of M81: Tracing the Spatial Distribution of Star Formation 25 Myr in the Past1

Davidge

2006

PUBL ASTRON SOC PAC

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“…The UCM dataset thus provides galaxy ellipticities (Pérez-González et al 2001), morphologies (Vitores et al 1996a) and E(B − V) colour excesses for a large number of galaxies. These can be used to investigate the dependence of internal extinction on galaxy inclination and morphology, which proved impossible with our Brγ observations.…”

Section: The Ucm Hα Surveymentioning

confidence: 99%

The Hα Galaxy Survey

James¹,

Shane²,

Knapen³

et al. 2005

A&A

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Abstract. We study the two main corrections generally applied to narrow-band Hα fluxes from galaxies in order to convert them to star formation rates, namely for [N] contamination and for extinction internal to the galaxy. From an imaging study using carefully chosen narrow-band filters, we find the [N] and Hα emission to be differently distributed. Nuclear measurements are likely to overestimate the contribution of [N] to total narrow-band fluxes. We find that in most star formation regions in galaxy disks the [N] fraction is small or negligible, whereas some galaxies display a diffuse central component which can be dominated by [N] emission. We compare these results with related studies in the literature, and consider astrophysical explanations for variations in the [N]/Hα ratio, including metallicity variations and different excitation mechanisms. We proceed to estimate the extinction towards star formation regions in spiral galaxies, firstly using Brγ/Hα line ratios. We find that extinction values are larger in galaxy nuclei than in disks, that disk extinction values are similar to those derived from optical emission-line studies in the literature, and that there is no evidence for heavily dust-embedded regions emerging in the near-IR, which would be invisible at Hα. The numbers of galaxies and individual regions detected in Brγ are small, however, and we thus exploit optical emission line data from the literature to derive global Hα extinction values as a function of galaxy type and inclination. In this part of our study we find only a moderate dependence on inclination, consistent with broad-band photometric studies, and a large scatter from galaxy to galaxy. Typical extinctions are smaller for late-type dwarfs than for spiral types. Finally, we show that the application of the type-dependent extinction corrections derived here significantly improves the agreement between star formation rates calculated using Hα fluxes and those from far-infrared fluxes as measured by IRAS. This again supports the idea that heavily dust-embedded star formation, which would be underestimated using the Hα technique, is not a dominant contributor to the total star formation rate of most galaxies in the local Universe.

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“…Gunn r and Johnson B observations were obtained in several observing runs from 1989 to 2001 using 1–2 m class telescopes at the German–Spanish Observatory of Calar Alto (CAHA, Almería, Spain) and the Observatorio del Roque de los Muchachos (La Palma, Spain). The observing details as well as the reduction and calibration procedures can be found in Vitores et al (1996a,b) for the r data, and in Pérez‐González et al (2000, 2001) for B . Briefly, the sample has average magnitudes of m B = 16.1 ± 1.1 ( M B =−19.2) and m r = 15.5 ± 1.0 ( M r =−19.8), with a mean B ‐band effective radius of 2.8 kpc.…”

Section: Datamentioning

confidence: 99%

“…Aiming to include the majority of the galaxy light, we used apertures with radii equal to three exponential disc scalelengths as determined in the r ‐band images (Vitores et al 1996b). In the few cases when the r ‐band bulge–disc decomposition was not available, we used the radius of the 24 mag arcsec 2 isophote measured in the B band ( r 24 ; Pérez‐González et al 2001). We inspected each image visually and checked that these apertures were encompassing all the detectable galaxy flux, and that no artefacts were disturbing the data.…”

Section: Datamentioning

confidence: 99%

“…We will also study in detail how well our modelling techniques are able to reproduce the observations. In Pérez‐González et al (2003a, hereafter Paper II), the second paper of the series, we will present the properties of the UCM galaxies derived using these data and techniques. Paper II will discuss the young and newly formed stars in the galaxies, together with the underlying population of evolved stars, the total stellar masses, etc.…”

Section: Introductionmentioning

confidence: 99%

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Stellar populations in local star-forming galaxies -- I. Data and modelling procedure

Pérez‐González

Paz

Zamorano

et al. 2003

Monthly Notices of the Royal Astronomical Society

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We present an analysis of the integrated properties of the stellar populations in the Universidad Complutense de Madrid (UCM) Survey of Hα-selected galaxies. In this paper, the first of a series, we describe in detail the techniques developed to model star-forming galaxies using a mixture of stellar populations, and taking into account the observational uncertainties. We assume a recent burst of star formation superimposed on a more evolved population. The effects of the nebular continuum, line emission and dust attenuation are taken into account. We also test different model assumptions including the choice of specific evolutionary synthesis model, initial mass function, star formation scenario and the treatment of dust extinction. Quantitative tests are applied to determine how well these models fit our multi-wavelength observations for the UCM sample. Our observations span the optical and near infrared, including both photometric and spectroscopic data. Our results indicate that extinction plays a key role in this kind of studies, revealing that low-and high-obscured objects may require very different extinction laws and must be treated differently. We also demonstrate that the UCM Survey galaxies are best described by a short burst of star formation occurring within a quiescent galaxy, rather than by continuous star formation. A detailed discussion on the inferred parameters, such as the age, burst strength, metallicity, star formation rate, extinction and total stellar mass for individual objects, is presented in paper II of this series.

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Optical photometry of the UCM lists I and II

Cited by 14 publications

References 37 publications

Red Supergiants in the Disk of M81: Tracing the Spatial Distribution of Star Formation 25 Myr in the Past1

Red Supergiants in the Disk of M81: Tracing the Spatial Distribution of Star Formation 25 Myr in the Past1

The Hα Galaxy Survey

Stellar populations in local star-forming galaxies -- I. Data and modelling procedure

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