Parametrization of the Galactic structure by two exponentials

Karaali, S.

doi:10.1002/asna.200510478

Cited by 4 publications

(7 citation statements)

References 26 publications

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“…Bahcall & Soneira (1980), Gilmore & Reid (1983), Majewski (1993), and Kroupa et al (1993). Analyses of deep imaging survey data using Galaxy disc models were completed by, for example, Phleps et al (2005), Ryan et al (2005), Karaali (2006), and Jurić et al (2008). The volume densities of the axisymmetric thin and thick discs depend on the galactocentric distance R and the height over or below the galactic plane, Z.…”

Section: The Galaxy Thin-disc Modelmentioning

confidence: 99%

Contamination by field late-M, L, and T dwarfs in deep surveys

Caballero

Burgasser

Klement

2008

A&A

108

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Context. Deep photometric surveys of substellar objects in young clusters and high-redshift quasars are affected by contaminant sources at different heliocentric distances. If not correctly taken into account, the contamination may have a strong effect on the Initial Mass Function determination and on the identification of quasars. Aims. We calculate in detail the back-and foreground contamination by field dwarfs of very late spectral types (intermediate and late M, L, and T) in deep surveys and provide the data and tools for the computation. Methods. We adopt the latest models and data from the literature, which include the following: (i) a model of the Galactic thin disc by an exponential law; (ii) the length and height scales of late-type dwarfs; and (iii) the local spatial densities, absolute magnitudes, and colours of dwarfs for each spectral type. Results. We derive a simplified expression for the spatial density in the thin disc that depends on the heliocentric distance and the galactic coordinates (l, b) and integrate this into the truncated cone studied in the survey. As a practical application, we compute the numbers of L-and T-type field dwarfs in very deep (I = 21−29 mag) surveys in the direction of the young σ Orionis cluster. The increasing number of contaminants at the faintest magnitudes could inhibit the study of the opacity mass limit at M < ∼ 0.003 M in the cluster.

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Section: The Galaxy Thin-disc Modelmentioning

confidence: 99%

Contamination by field late-M, L, and T dwarfs in deep surveys

Caballero

Burgasser

Klement

2008

A&A

108

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“…Therefore, we have estimated the back-and/or foreground contamination in our I J survey only by non-member field-dwarf contaminants of very late spectral types (intermediate-and late-M, L, and T). Up-to-date models and data from the literature have been used: (i) a model of the Galactic thin disc by an exponential law (Phleps et al 2005;Ryan et al 2005;Karaali 2006); (ii) the length and height scales for late-type dwarfs in the Galaxy (Chen et al 2001); (iii) the spatial densities, absolute magnitudes and colours of ultracool dwarfs for each spectral type (Kirkpatrick et al 1994;Dahn et al 2002;Cruz et al 2003;Vrba et al 2004;Nakajima 2005).…”

Section: Contamination By Fore-and Background Sourcesmentioning

confidence: 99%

The substellar mass function in sigma Orionis. II. Optical, near-infrared and IRAC/Spitzer photometry of young cluster brown dwarfs and planetary-mass objects

Caballero,

Béjar,

Rebolo

et al. 2007

Preprint

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Aims. We investigate the mass function in the substellar domain down to a few Jupiter masses in the young σ Orionis open cluster (3±2 Ma, d = 360 +70 −60 pc). Methods. We have performed a deep I J-band search, covering an area of 790 arcmin 2 close to the cluster centre. This survey was complemented with an infrared follow-up in the HK s -and Spitzer 3.6-8.0 µm-bands. Using colour-magnitude diagrams, we have selected 49 candidate cluster members in the magnitude interval 16.1 mag < I < 23.0 mag. Results. Accounting for flux excesses at 8.0 µm and previously known spectral features of youth, 30 objects are bona fide cluster members. Four are first identified from our optical-near infrared data. Eleven have most probable masses below the deuterium burning limit and are classified as planetary-mass object candidates. The slope of the substellar mass spectrum (∆N/∆M ≈ aM −α ) in the mass interval 0.11 M ⊙ < M < 0.006 M ⊙ is α = +0.6 ± 0.2. Any opacity mass-limit, if these objects form via fragmentation, may lie below 0.006 M ⊙ . The frequency of σ Orionis brown dwarfs with circumsubstellar discs is 47±15 %. Conclusions. The continuity in the mass function and in the frequency of discs suggests that very low-mass stars and substellar objects, even below the deuterium-burning mass limit, may share the same formation mechanism.

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“…Therefore, we estimate the contamination fraction in our IJ survey only from background and foreground non-member field dwarfs of very late spectral types (intermediate-and late-M, L, and T). This we base on up-to-date models and data from the literature: (i) an exponential model for the Galactic thin disc (Phleps et al 2005;Ryan et al 2005;Karaali 2006); (ii) the length and height scales for late-type dwarfs in the Galaxy (Chen et al 2001); (iii) the spatial densities, absolute magnitudes and colours of ultracool dwarfs for each spectral type (Kirkpatrick et al 1994;Dahn et al 2002;Cruz et al 2003;Vrba et al 2004;Nakajima 2005). Table 6 shows the resulting possible contaminants listed in approximately 1 mag-wide bins.…”

Section: Contamination By Fore-and Background Sourcesmentioning

confidence: 99%

The substellar mass function inσ Orionis

Caballero

Béjar

Rebolo

et al. 2007

A&A

127

207

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Aims. We investigate the mass function in the substellar domain down to a few Jupiter masses in the young σ Orionis open cluster (3 ± 2 Ma, d = 360 +70 −60 pc). Methods. We have performed a deep IJ-band search, covering an area of 790 arcmin 2 close to the cluster centre. This survey was complemented with an infrared follow-up in the HK s -and Spitzer 3.6-8.0 µm-bands. Using colour-magnitude diagrams, we have selected 49 candidate cluster members in the magnitude interval 16.1 mag < I < 23.0 mag. Results. Accounting for flux excesses at 8.0 µm and previously known spectral features of youth, we identify 30 objects as bona fide cluster members. Four are first identified from our optical-near infrared data. Eleven have most probable masses below the deuterium burning limit which we therefore classify as candidate planetary-mass objects. The slope of the substellar mass spectrum (∆N/∆M ≈ aM −α ) in the mass interval 0.11 M < M < 0.006 M is α = +0.6 ± 0.2. Any mass limit to formation via opacity-limited fragmentation must lie below 0.006 M . The frequency of σ Orionis brown dwarfs with circumsubstellar discs is 47±9 %. Conclusions. The continuity in the mass function and in the frequency of discs suggests that very low-mass stars and substellar objects, even below the deuterium-burning mass limit, share the same formation mechanism.

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Parametrization of the Galactic structure by two exponentials

Cited by 4 publications

References 26 publications

Contamination by field late-M, L, and T dwarfs in deep surveys

Contamination by field late-M, L, and T dwarfs in deep surveys

The substellar mass function in sigma Orionis. II. Optical, near-infrared and IRAC/Spitzer photometry of young cluster brown dwarfs and planetary-mass objects

The substellar mass function inσ Orionis

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